# U.S. Pressure Tank Drawdown Test: Measure Usable Water

Source: https://brictale.com/water/pressure-tanks/pressure-tank-drawdown-test
Published: 2026-08-22
Audience: Homeowner
Published by Brictale, a consumer home-intelligence publication. https://brictale.com

## Short answer

This U.S.-only worksheet measures gallons delivered between pump shutoff and restart. Record the tank model, observed cut-in and cut-out pressures, collected gallons, refill time, and conditions. Run it only on a documented conventional discrete cycle from a normal tool-free cold fixture. Compare a manufacturer table only when model and pressure band match; a low result needs professional diagnosis.

---

U.S.-only scope: this worksheet uses U.S. CDC/EPA guidance, state-certified drinking-water laboratories, and U.S. plumbing, electrical, discharge, licensing, permit, and code terminology. If you are outside the United States, stop at this jurisdiction gate and use the applicable local health or environmental authority, laboratory, and qualified trade professional before relying on the workflow.

The useful number in a pressure-tank drawdown test is not the number printed on the tank label. It is the gallons you can collect after the pump stops and before it starts again, under a recorded pressure band. A correct comparison needs four matches: the exact tank model, the observed cut-in pressure, the observed cut-out pressure, and the test conditions. If any of those are unknown, the result is a measurement record—not a tank verdict.

Use the flow on this page to decide which of four outcomes fits your evidence:

| Result | What it supports | Safest next step |
|---|---|---|
| Observed drawdown matches the manufacturer's value for the exact model and pressure band | The tank is delivering the published usable volume under this test | If cycling is still bothersome, investigate demand, pump output, controls, or whether the tank is undersized for the system |
| Observed drawdown is reproducibly lower, and model and pressures match | Lost usable volume or a test/setup problem is plausible | Give the record to a qualified well professional for gauge, tank, valve, and precharge diagnosis |
| Observed drawdown is stable but small for the home's demand | The tank may be functioning but undersized for the pump and household pattern | Ask for a pump-cycle and tank-sizing review; do not call the tank failed from gallons alone |
| Model, pressure band, or conditions do not match | Published comparison is invalid | Repeat with better records or have the professional identify the correct table |

This is a comparison worksheet, not a universal pass/fail calculator. Manufacturer tables vary by model and operating range. For example, Pentair lists a Simer LT2 with 5 gallons of maximum capacity but only 0.6 gallons of drawdown with a 30/50 pressure switch; the same page lists 0.7 gallons at 20/40. That is why “two-gallon tank,” “five-gallon tank,” or another nominal label cannot stand in for usable water. ([Pentair's Simer LT2 specifications](https://www.pentair.com/en-us/products/residential/water-supply-disposal/water-supply-pumps/simer-lt2-2-gallon-vertical-pre-charged-pressure-tank.html))

## 1. Know what the test measures

A precharged pressure tank stores water against an air charge so the pump does not need to start for every small demand. Drawdown is the water delivered between pump shutoff and pump restart. It is an operating-volume observation, not the tank's shell volume, rated equivalency, or advertised maximum capacity.

The measurement has two events:

1. The pump stops at the system's cut-out pressure.
2. A fixture delivers water until the pump starts at the system's cut-in pressure.

The gallons collected between those events are the observed drawdown for that test. LAKOS uses this same stop-to-restart idea in its bucket procedure, directing the user to let the system refill, collect water until the pump turns back on, then time how long the pump takes to refill that measured amount. ([LAKOS's bucket-test procedure](https://www.lakos.com/resources/bucket-test/))

The refill portion is useful context. If you collect (G) gallons and the pump takes (T) minutes to return to shutoff, the observed refill rate is:

```text
observed refill rate (gallons per minute) = G ÷ T
```

That rate is only the observed pump-and-system result under the recorded conditions. It is not automatically the pump's rated flow, the well's sustainable yield, proof that the tank is healthy, or evidence of any particular fault. A longer or shorter refill than a prior baseline is a reason to preserve the record for professional investigation, not a diagnosis.

The pressure band matters because the tank's air-water relationship changes as pressure changes. Goulds/CentriPro publishes drawdown tables that use a pressure factor multiplied by total tank volume, with named values for specific models and pressure ranges. The same table says its figures are based on a 22 psi differential and Boyle's law, and that temperature, elevation, and pressure can affect drawdown. ([Goulds/CentriPro's tank-selection data](https://www.xylem.com/siteassets/brand/centripro/resources/manual/bmaid.pdf))

That gives you three distinct questions:

- Is the tank providing the usable gallons its own table predicts at the pressure band actually observed?
- Is that amount enough to keep the pump from starting too often for the home's real demand?
- Is another part of the system consuming or interrupting the drawdown before the tank can deliver it?

Only the first question is answered by a model-matched drawdown comparison. The other two require the cycle record and system context.

## 2. Set the safety boundary before collecting water

The homeowner-safe part of this test is observation and water collection from one normal, tool-free cold-water fixture. Do not turn a bucket test into pressure-switch service.

Stop and arrange qualified help if you see a leaking, bulging, deeply corroded, or damaged tank; uncontrolled pressure; a relief valve discharging; sparking; hot, wet, or damaged wiring; a pump that appears to run without water; or water near electrical equipment. Do not continue merely because the faucet still works.

Brictale's remote-guide boundary is deliberately conservative: do not open, remove, or access any pressure-switch or control enclosure, whether power is on, supposedly off, or isolated. Only qualified personnel may isolate power, verify isolation, or service that enclosure. Do not touch live wiring, bypass a control, adjust a pressure switch, pull a pump, open a well, enter a well pit or other confined space, manipulate pressurized equipment, remove a gauge, or add air to a tank as part of this homeowner test. This is Brictale's scope limit, not a claim that one product manual establishes a universal work rule.

Treat the bucket-test water as non-potable unless you already know the supply is safe. Do not taste it or use it for drinking, cooking, ice, brushing teeth, washing dishes, washing, bathing, handwashing, or pets. If chemical contamination is suspected—or you cannot rule it out—stop the test and do not touch, wash with, give to pets, or otherwise use the water. Do not attempt to contain, drain, disinfect, or dispose of it yourself; ask the local health or environmental authority for the containment, disposal, testing, and return-to-use instructions. If microbiological contamination is suspected, also stop use and contact that authority. Use a state-certified drinking-water laboratory only as directed before returning the water to use. CDC says chemically contaminated water should not be used for any purpose because touching or other contact may be dangerous; EPA directs homeowners to certified drinking-water laboratories and local authorities for well-specific advice. ([CDC well-water treatment guidance](https://www.cdc.gov/drinking-water/safety/guidelines-for-treating-well-water.html), [EPA private-well testing guidance](https://www.epa.gov/privatewells/protect-your-homes-water))

Amtrol's manual warns that a tank can corrode, leak, flood, rupture, or in rare cases explode, and says qualified professionals should install and periodically inspect and service the unit. Its warnings specifically say not to add or adjust precharge when there is visible exterior corrosion, loss of air, or a reduction in pump cycle time; the manual assigns checking, adjusting, or recharging precharge to qualified professionals. ([Amtrol's precharged well-tank safety instructions](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf))

The tank's visible label is useful evidence, but it is not permission to work on the tank. Photograph the label from a dry, stable location. Record the model and serial or date code if legible. Keep the tank's rated pressure and the installed system's limits separate from the test result. Amtrol's 125 psig rating, for example, applies to the referenced Amtrol well-tank line; it must not be copied to another model. ([Amtrol's pressure and product-safety limits](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf))

Before collecting water, identify the exact tank/system pressure rating from the label or current manual and whether required relief protection is known to be present. Stop immediately and obtain qualified service if observed pressure is at or above that exact rating, the rating is unknown, relief protection is absent or unknown, or a relief device is discharging. Do not inspect, test, adjust, remove, or discharge through the relief valve yourself. The referenced Amtrol manual requires the system to stay below its rated pressure and requires a properly sized relief valve; those limits are model-specific, so unknown protection is not a safe basis for a homeowner test. ([Amtrol's pressure and relief-valve requirements](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf))

For the water collection itself, use only a normal, tool-free cold-water fixture downstream of the tank, a container whose volume is known well enough to record uncertainty, and a timer. Do not use a tank drain, relief-valve outlet, gauge or air-valve connection, hot-water outlet, or any fixture or timer setup near electrical equipment. Keep the container on the floor or another stable surface if lifting it could cause a spill. Use only one fixture. Make sure the discharge will not flood a room, damage a drain, or contact electrical equipment.

Before opening the faucet, confirm a lawful, ordinary discharge destination for the water and volume under local requirements. If you cannot confirm one without manipulating plumbing, do not run the worksheet. If contamination is suspected, stop and ask the local health or environmental authority for containment and disposal instructions. EPA supports using certified drinking-water laboratories and contacting local health or environmental authorities for well-specific guidance; this page does not infer a universal household discharge rule from that guidance. ([EPA private-well protection guidance](https://www.epa.gov/privatewells/protect-your-homes-water))

This observation worksheet is not authorization to install, service, or discharge water. Plumbing, electrical, well, pressure-vessel, discharge, permit, inspection, and professional-licensing requirements vary by jurisdiction. Follow the authority having jurisdiction, the current instructions for the exact manufacturer and model, and a qualified local professional. The Amtrol manual likewise requires applicable local and state codes and qualified professional installation and service; its instructions are not a universal code for another tank. ([Amtrol's local-code and professional-service instructions](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf))

The test should be postponed when irrigation, a water softener or filter is regenerating, a dishwasher or washing machine is running, livestock demand is active, or another person may use water. Those demands can consume some of the tank water between the two pressure events, so the bucket reading is lower than the tank's total delivered water and the direct comparison is invalid.

## 3. Fill out the measurement worksheet first

Write the record before opening the faucet. A professional can do more with a dated, repeatable record than with “the pump cycles fast.” Use one line for each trial.

### System identity

| Field | Record |
|---|---|
| Test date and time | ______________________________ |
| Tank manufacturer | ______________________________ |
| Exact tank model | ______________________________ |
| Serial number or date code | ______________________________ |
| Tank label volume or capacity wording | ______________________________ |
| Tank condition from safe visual inspection | dry / wet / corroded / bulged / unknown |
| Pump type if known | single-speed conventional / variable-speed / constant-pressure / unknown |
| Pressure control type | mechanical switch / electronic sensor / unknown |
| Gauge location and units | ______________________________ |
| Faucet or valve used | ______________________________ |
| Exact tank/system pressure rating | ______________________________ |
| Relief protection known present? | yes / no / unknown |

Do not substitute a brand family, color, diameter, or “about 20 gallons” for an exact model. If the label is unreadable, enter “unknown.” A table for one model cannot validate another model with a similar nominal size.

### Pressure and cycle observations

| Field | Trial 1 | Trial 2 | Trial 3 |
|---|---:|---:|---:|
| Pump stop / cut-out pressure | ______ psi | ______ psi | ______ psi |
| Pump restart / cut-in pressure | ______ psi | ______ psi | ______ psi |
| Gallons collected, stop to restart | ______ gal | ______ gal | ______ gal |
| Refill time, restart to stop | ______ min | ______ min | ______ min |
| Observed refill rate | ______ gpm | ______ gpm | ______ gpm |
| Gauge behavior | smooth / flutter / stuck / unknown | smooth / flutter / stuck / unknown | smooth / flutter / stuck / unknown |
| Notes on air, sediment, pressure pause, or flow change | __________________ | __________________ | __________________ |

Record what the gauge actually showed, even if it differs from a familiar “30/50” assumption. A 31/49 reading is not the same evidence as a verified 30/50 band. If the gauge is damaged, unreadable, or moving erratically, mark the pressure as unverified instead of forcing a comparison.

### Test conditions and uncertainty

Record whether all other fixtures were closed, whether treatment equipment was idle, whether irrigation was off, and whether the water source was stable. Also record the container's usable measurement increment and your timing method.

```text
Container or meter: ______________________________
Smallest marked volume: __________________ gallons
Estimated volume uncertainty: ±__________________ gallons
Timer method: ____________________________________
Estimated timing uncertainty: ±__________________ seconds
Other water use: none / yes / unknown
Recent service, outage, drought, freezing, or plumbing change:
__________________________________________________
```

The worksheet should preserve uncertainty instead of creating false precision. If your container is marked only in half-gallon increments, report “about 3.5 gallons” or an explicit range rather than “3.47 gallons.” If the pump restarted while you were looking away, mark the trial as approximate.

## 4. Run the bucket test without changing the controls

The sequence below is for a normal, tool-free cold-water fixture. It does not require opening a pressure switch or touching wiring.

{{visual:drawdown-cycle-map}}

### Preflight: confirm a comparable cycle

Run this worksheet only when the exact pump and control documentation describes a normal, discrete pump-stop and pump-restart sequence with a conventional cut-out and cut-in pressure. Variable-speed, constant-pressure, transducer-controlled, or other systems without that documented cycle are out of scope. Do not open an enclosure or force a cycle to make the worksheet fit; record “not comparable” and hand the system to a qualified professional. LAKOS's bucket sequence itself assumes that the pump turns on, shuts off, and turns back on at distinct events. ([LAKOS's conventional bucket-test sequence](https://www.lakos.com/resources/bucket-test/))

### Step 1: check conditions without changing the plumbing

Do not close or move an unidentified shutoff, bypass, check, filter, treatment, pressure, or other valve. Do not change the plumbing or controls. The homeowner-safe way to reduce competing demand is to schedule the test when ordinary fixtures, irrigation, and appliances are not being used and to confirm that treatment equipment is not regenerating or backwashing. If a device must remain active, record it; if you cannot establish the conditions without manipulating components, mark the trial unknown and arrange qualified diagnosis.

### Step 2: establish pump stop

Before opening the selected faucet, check whether the pump is already running continuously, failing to build pressure, or appearing to run dry. Any of those is a stop condition: do not start the bucket test, do not alter a valve or control, and arrange qualified service. Also stop if the observed pressure is at or above the exact tank/system rating, the rating is unknown, or relief protection is absent or unknown.

Open the selected faucet and let water run until the pump starts. Close the faucet and allow the system to refill until the pump stops. LAKOS describes this refill-to-shutoff setup before the measured collection step. ([LAKOS's refill-to-shutoff sequence](https://www.lakos.com/resources/bucket-test/))

Watch the gauge from a safe position. Write down the pressure at which the pump stops. If the pump does not stop, the gauge does not move toward shutoff, the pressure is uncontrolled, or the faucet flow becomes abnormal, stop the test and record the condition for a professional.

### Step 3: collect gallons until restart

Use the same normal, tool-free cold-water fixture. Place the container so it will not tip. Open the fixture and collect water continuously. Record the total volume delivered when the pump starts again. Close the fixture promptly after restart.

This is the observed drawdown: water from pump stop to pump restart. The first trial may be rough because the container is hard to read or the restart is easy to miss. Keep it as a baseline, then repeat only if the system remains safe and the conditions can be kept the same.

Do not keep collecting after restart and call the total “tank size.” Once the pump starts, the pump is contributing water and the test is no longer measuring tank-only delivery. Do not leave the faucet open while walking away.

### Step 4: time the refill

After the pump starts, close the faucet and start the timer as consistently as you can. Time from restart until the pump stops again. LAKOS's procedure uses the measured collected volume and the refill time to calculate gallons per minute. ([LAKOS's measured-volume and refill-time calculation](https://www.lakos.com/resources/bucket-test/))

If you started the timer late, write that down. Timing error matters more for a short refill than for a long one. The refill rate is context, not a hidden pass/fail test.

### Step 5: repeat for consistency

A second and third trial are useful only if they use the same faucet, no competing demand, the same stop-to-restart definition, and similar pressure readings. Compare the trial results:

```text
repeatability spread = highest observed gallons − lowest observed gallons
average observed gallons = (trial 1 + trial 2 + trial 3) ÷ number of valid trials
```

If the spread is large, do not average it away. Record the range and look for reasons: inconsistent faucet opening, an early or late restart, a pressure gauge that sticks, another demand starting, a treatment valve changing position, or a well recovering between trials. A variable result is a reason to improve the measurement or call a professional, not a reason to select the smallest number because it sounds worse.

## 5. Match the result to the right manufacturer table

The comparison calculator should have a deliberate “not comparable” state. It should not estimate a published drawdown from a nominal tank volume when the exact table is missing.

{{visual:drawdown-comparison-matrix}}

### Required comparison fields

Enter these side by side:

| Published-table field | Observed-test field |
|---|---|
| Exact manufacturer and model | Manufacturer and model from the installed label |
| Published operating band | Observed cut-in and cut-out pressures |
| Published drawdown in gallons | Collected gallons from stop to restart |
| Table notes and assumptions | Faucet, demand, gauge, date, and uncertainty |

The comparison is eligible only when the installed model is identified and the observed pressure band corresponds to the manufacturer's published band. “30/50” must mean cut-in 30 psi and cut-out 50 psi for the comparison; a nearby but unverified pressure range should be flagged.

Goulds/CentriPro demonstrates why this discipline matters. Its data includes different drawdown values for different models and pressure ranges, and explains that a factor is multiplied by the total tank volume to calculate drawdown. Its example calculates a V-200 tank at 35/55 psi as 65.1 gallons of total volume times a pressure factor of .29, or 18.9 gallons of drawdown. That example belongs to the named tank-selection data; it is not a universal formula for every pressure tank. ([Goulds/CentriPro's model-specific drawdown example](https://www.xylem.com/siteassets/brand/centripro/resources/manual/bmaid.pdf))

Use these worksheet formulas only after the match is confirmed:

```text
observed drawdown = measured gallons from stop to restart
difference = observed drawdown − published drawdown
relative difference = difference ÷ published drawdown
```

The relative difference is descriptive, not a manufacturer acceptance limit. Do not insert an invented “within 10 percent” rule. The table itself may have assumptions, and the measurement has container, timing, gauge, and event-detection uncertainty. Goulds/CentriPro explicitly notes that temperature, elevation, and pressure can affect drawdown, so a small discrepancy is not automatically a failed tank. ([Goulds/CentriPro's drawdown limitations note](https://www.xylem.com/siteassets/brand/centripro/resources/manual/bmaid.pdf))

### Worked example: a matched comparison

Suppose the installed label is confirmed as the Pentair Simer LT2, the gauge shows a verified 30/50 band, and three safe trials measure 0.55, 0.60, and 0.65 gallons. Pentair lists 0.6 gallons of drawdown at 30/50 for that model. The average is 0.60 gallons and the spread is 0.10 gallons. If the container uncertainty is approximately ±0.05 gallons, the measurements are consistent with the published figure at the resolution of this home test.

That conclusion is narrow: the tank delivered about the listed drawdown under that test. It does not prove the bladder is new, the pressure switch is healthy, the gauge is calibrated, the pump is correctly sized, or the system has enough drawdown for the home's demand. The Pentair page also marks this product discontinued, which is a reminder to use the installed model's current documentation rather than assuming a replacement with a similar label has the same table. ([Pentair's Simer LT2 model and drawdown data](https://www.pentair.com/en-us/products/residential/water-supply-disposal/water-supply-pumps/simer-lt2-2-gallon-vertical-pre-charged-pressure-tank.html))

### When the comparison must stop

Stop the numerical comparison if the model is unknown, the gauge band is unknown, the table is for a different model, the pressure band differs, the exact pressure rating is unknown, relief protection is absent or unknown, the tank is visibly damaged, the system is variable-speed/constant-pressure or otherwise lacks a documented discrete cycle, the pump did not complete a normal cycle, or the collection included pump-delivered water. Choose “not comparable” and preserve the record.

## 6. Interpret the result without overdiagnosing the tank

The same small amount of collected water can mean different things. Use the matrix below to decide what to ask next.

| What you observed | What it may mean | What it does not prove | Next action |
|---|---|---|---|
| Stable gallons, matched table, frequent starts during normal use | Tank may be functioning but the usable volume may be small for pump flow or household demand | It does not prove a replacement is needed | Ask for cycle-frequency, pump-flow, and sizing review |
| Lower gallons on repeat trials with matched model and pressure band | A system condition or test/setup issue needs professional isolation | It does not identify a failed component | Provide records; request professional verification before parts are selected |
| Gallons change substantially between trials | Event timing, gauge behavior, competing demand, treatment cycle, or well condition may be affecting the test | It does not establish tank failure | Repeat under controlled conditions or use professional instruments |
| Pressure falls while no faucet is open | The observation needs professional investigation | It does not prove the tank is waterlogged or identify a cause | Do not manipulate unidentified valves; document ordinary demand and arrange diagnosis if pressure repeatedly drops |
| Pump will not stop | The system is outside this worksheet's safe scope | It does not prove the tank caused it | Stop bucket testing and obtain professional service |
| Tank shell leaks, bulges, or has significant corrosion | Pressure-vessel integrity is in question | It does not justify adding air or tightening fittings | Keep clear and use qualified service |

### Undersized but functioning

A functioning tank can be a poor fit for a system. If the measured drawdown is repeatable and close to the correct published value, but the pump still starts often during normal use, the tank may simply supply too few usable gallons for the pump's output or the home's demand pattern. A small amount of drawdown can be completely normal for a small tank. The design question is whether the cycle frequency and run duration are acceptable for the pump and controls.

Do not “fix” this conclusion by comparing the measured gallons with the tank's advertised shell volume. Discuss the pump's minimum run-time guidance, actual flow, pressure settings, demand, well yield, and available tank models with a professional. A larger tank may alter cycling; it does not repair a leak, a clogged restriction, a failed gauge, or a low-yield well.

### Lost usable volume

Lost usable volume becomes a stronger lead when the exact model is known, the pressure band matches the table, the gauge has been verified or its limitation is documented, competing demand was off, and repeat trials are consistently below the published value by more than the measurement uncertainty. Even then, the result identifies a problem to isolate; it does not identify the failed part.

The bucket result cannot determine the cause. It may reflect the tank, another system condition, or the test setup, but this worksheet does not rank those possibilities or select a failed part. Amtrol's manual is specifically conservative about adding pressure to an in-service tank after reduced cycle time or air loss because those signs can coexist with internal corrosion. ([Amtrol's warning about reduced cycle time, air loss, and corrosion](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf))

The correct next step is verification, not a universal pass/fail threshold. Ask the professional to explain which observation isolates the tank and which remaining alternatives were checked.

## 7. Treat precharge as a professional test record

Precharge is important to the comparison, but it is not part of the homeowner bucket procedure. Do not remove the air-valve cap, attach a gauge, add air, release air, drain a tank, or open or access a control enclosure under any circumstances as a homeowner. Only qualified personnel may isolate power, verify isolation, or service the enclosure and tank.

Amtrol's referenced instructions give a common example—precharge 2 psi below the pressure-switch cut-in—and show 28 psi for a 30/50 setting. That is an equipment instruction and example, not permission to apply 2 psi below cut-in to every tank or control strategy. ([Amtrol's precharge example](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf))

If a professional performs the precharge check, add these fields to the worksheet:

| Precharge record | Value |
|---|---|
| Who performed the check and date | ______________________________ |
| Exact tank model and condition confirmed | ______________________________ |
| Pump power isolation method | ______________________________ |
| Water pressure drained to | __________________ psi |
| Precharge instrument and stated accuracy | ______________________________ |
| Measured precharge | __________________ psi |
| Cut-in and cut-out used for comparison | ______ / ______ psi |
| Manufacturer procedure or manual section | ______________________________ |
| Visible corrosion, leakage, or water at air valve | ______________________________ |
| Adjustment made? | no / yes—professional record attached |

The condition “water pressure drained to zero” matters because an air reading taken while the tank remains pressurized with water is not the same as the specified precharge test condition. The pressure source and instrument also matter. If the professional cannot confirm the tank's integrity, the safe answer may be replacement or further inspection rather than adding air.

Do not infer bladder failure from a single air reading. Do not infer a healthy tank from a correct precharge reading. Precharge is one branch in a system diagnosis that also includes the gauge, pressure control, check valves, pump, well supply, piping, and household demand.

## 8. Hand off a decision-ready record and repeat it after service

Bring the following to a well or pump professional:

- A clear photograph of the tank label, model, serial or date code, and accessible gauge.
- The exact faucet or valve used and whether it was downstream of treatment equipment.
- At least one complete stop-to-restart drawdown record.
- Cut-in and cut-out pressures as observed, not assumed.
- Gallons collected, refill time, and calculated refill rate.
- Container graduations, timing method, and estimated uncertainty.
- Whether other water use, irrigation, treatment regeneration, or a leak could have been active.
- Visible corrosion, wetness, bulging, discharge, unusual noise, air, sediment, or pressure flutter.
- Recent pump, tank, switch, gauge, filter, softener, plumbing, electrical, weather, or well changes.
- Any precharge record performed by a qualified professional.

Ask the professional to separate three decisions on the estimate:

1. Is the measured drawdown inconsistent with the exact tank table under matched settings?
2. Is the tank functioning but undersized for the pump and demand?
3. Is another system fault causing the short cycle or pressure symptom?

Those are different scopes. “Replace the tank” may be reasonable when integrity is compromised, but tank replacement is not a substitute for finding a leak, clearing a restriction, checking a control, measuring pump performance, or evaluating the well. A correctly sized replacement can also give the wrong result if the pressure settings or system configuration differ from the published assumptions.

### Acceptance record after service

If a repair or replacement is approved, define the retest before the work begins:

| Acceptance item | Before service | After service | Notes |
|---|---:|---:|---|
| Tank model and pressure rating | __________ | __________ | __________________ |
| Cut-in pressure | __________ | __________ | __________________ |
| Cut-out pressure | __________ | __________ | __________________ |
| Drawdown gallons | __________ | __________ | __________________ |
| Refill time | __________ | __________ | __________________ |
| Pressure holds with known demand off | yes / no / unknown | yes / no / unknown | __________________ |
| Visible leaks or corrosion | __________ | __________ | __________________ |
| Short-cycle symptom under the same demand | __________ | __________ | __________________ |

Use the same faucet, container, pressure observation point, and demand conditions after service when practical. If the model or pressure settings changed, use the new manufacturer's documentation; do not compare a new configuration with the old table merely because the tank looks similar.

### Simple maintenance baseline

The most useful repeat test is not a frequent ritual. It is a baseline after normal service and a repeat when the system's behavior changes. Record the cycle under one known demand pattern, then watch for these triggers:

| Trigger | Record or action |
|---|---|
| Pump begins starting during small draws | Time one cycle and record gallons if safe; do not adjust controls |
| Pressure falls while the home is idle | Check for ordinary demand and document the gauge trend; arrange diagnosis if repeated |
| Refill takes longer than the baseline | Record demand, weather, treatment status, and pressure behavior |
| New leak, corrosion, bulging, or relief discharge | Stop and seek qualified service |
| Tank, gauge, switch, pump, filter, or treatment work | Repeat the documented acceptance test |
| Model or pressure settings are changed | Start a new baseline and obtain the correct table |

The end state is a repeatable measurement a professional can trust: exact equipment identity, observed pressure band, measured usable gallons, refill time, and uncertainty. That record can help separate a table-consistent small tank from a repeatably low result when the model and pressure band match, but it cannot diagnose the cause of a low result. It can prevent a nominal-gallon assumption from driving an unnecessary replacement while keeping the homeowner on the safe side of the boundary: observe, measure water, document the cycle, and stop before live electrical work, pressure-switch adjustment, tank pressurization, well access, pump removal, or other hazardous service.

## Evidence

- [LAKOS — Bucket Test](https://www.lakos.com/resources/bucket-test/) — LAKOS's homeowner-facing bucket-test procedure for measuring system flow and drawdown; use the sequence only at an accessible downstream valve and without opening controls.
- [LAKOS — Bucket Test](https://www.lakos.com/resources/bucket-test/) — LAKOS's calculation for the measured bucket-test interval; it does not establish pump capacity, well yield, or a tank-failure threshold.
- [Amtrol — Precharged Well Tanks Installation, Operation & Maintenance Instructions](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf) — Amtrol precharged well-tank instructions and example; the exact procedure depends on the tank, controls, and safety condition.
- [Amtrol — Precharged Well Tanks Installation, Operation & Maintenance Instructions](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf) — Amtrol safety warnings for its precharged well tanks; this is not a national code or a universal instruction for every tank design.
- [Amtrol — Precharged Well Tanks Installation, Operation & Maintenance Instructions](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf) — The referenced Amtrol manual and tank line only; do not apply its pressure rating to another model.
- [Goulds Water Technology — Motor Application and Installation Data](https://www.xylem.com/siteassets/brand/centripro/resources/manual/bmaid.pdf) — Goulds HydroPro and CentriPro tank-selection tables in the manual; model names, pressure factors, and values are manufacturer-specific.
- [Goulds Water Technology — Motor Application and Installation Data](https://www.xylem.com/siteassets/brand/centripro/resources/manual/bmaid.pdf) — The limitations note attached to the cited Goulds/CentriPro drawdown table; it supports uncertainty and matching cautions, not a universal correction factor.
- [Pentair — Simer LT2 2 Gallon Vertical Pre-Charged Pressure Tank](https://www.pentair.com/en-us/products/residential/water-supply-disposal/water-supply-pumps/simer-lt2-2-gallon-vertical-pre-charged-pressure-tank.html) — Pentair's current product page for the discontinued Simer LT2 model; the listed values apply only to that product and stated switch settings.
- [Pentair — Simer LT2 2 Gallon Vertical Pre-Charged Pressure Tank](https://www.pentair.com/en-us/products/residential/water-supply-disposal/water-supply-pumps/simer-lt2-2-gallon-vertical-pre-charged-pressure-tank.html) — Product construction description for the Simer LT2 only; it does not diagnose the condition of a tank installed at a home.
- [CDC — Guidelines for Treating Well Water](https://www.cdc.gov/drinking-water/safety/guidelines-for-treating-well-water.html) — U.S. CDC private-well treatment and emergency guidance; this supports the no-use/no-contact chemical-contamination boundary and escalation to the local authority, not a diagnosis from appearance alone.
- [EPA — Protect Your Home's Water](https://www.epa.gov/privatewells/protect-your-homes-water) — U.S. EPA private-well protection and testing guidance; the page also discusses certified laboratories, stormwater, wastewater, and local agencies, so it supports a U.S. local-authority handoff rather than a universal discharge route.
- [Amtrol — Precharged Well Tanks Installation, Operation & Maintenance Instructions](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf) — U.S.-specific local-code and qualified-professional warnings for the referenced tank line; jurisdiction-specific authorities and the installed model's current instructions control.
- [Amtrol — Precharged Well Tanks Installation, Operation & Maintenance Instructions](https://www.amtrol.com/wp-content/uploads/2019/07/9015-939-04_18-Precharged-Well-Tanks-IO.pdf) — Model-specific pressure and relief-protection requirements from the referenced Amtrol manual; supports stopping when the exact rating or relief protection is unknown, not applying 125 psi or a 100 psi relief value to another model.
- [LAKOS — Bucket Test](https://www.lakos.com/resources/bucket-test/) — The cycle assumptions explicitly shown in LAKOS's homeowner-facing procedure; variable-speed and constant-pressure systems require their exact manufacturer's procedure or qualified diagnosis.
- [Goulds Water Technology — Motor Application and Installation Data](https://www.xylem.com/siteassets/brand/centripro/resources/manual/bmaid.pdf) — Qualified-personnel and electrical-control warnings for Aquavar Solo2 controller troubleshooting in the referenced Goulds/CentriPro manual; this does not establish a universal rule for every pressure-switch or control enclosure.