How do I tell if my pressure tank is waterlogged?

Tap on the side of the tank with a knuckle or small wrench. A healthy tank sounds hollow on the top half (air) and solid on the bottom half (water). If the tank sounds solid all the way to the top and is heavy to push, or if water squirts out of the Schrader air valve when depressed, the internal bladder has ruptured and the tank must be replaced.

Why must well pumps run for at least 60 seconds per cycle?

Submersible motors rely on water flowing past the motor shroud to cool the electrical windings. Electric motors draw 5 to 7 times their running amperage during startup. Running for at least 1 to 2 minutes allows the starting heat spike to dissipate in the cool well water.

Can I install two pressure tanks together?

Yes! Plumbing two smaller tanks in parallel with a tee fitting delivers the exact same drawdown volume as one giant tank. Both tanks must have their air pre-charge calibrated to the exact same PSI (2 PSI below switch cut-in).

How often should I check pressure tank air pre-charge?

Check air pre-charge at least once a year. Over time, air molecules slowly permeate through the rubber membrane (losing 1 to 2 PSI per year). Always turn off the well pump and open a drain valve so tank water pressure is at 0 PSI before checking or adding air.

What happens if the air pre-charge pressure is too low?

If air pre-charge drops too low, the rubber bladder expands excessively during the 60 PSI cycle, rubbing against the rough steel inner tank wall, leading to premature bladder abrasion and tearing.

Free Water Well Pressure Tank Drawdown Calculator

🚰 Well Pump & Switch Settings

Well Pump Flow Rate (GPM) Pump delivery rating

Pressure Switch Cut-In / Cut-Out

Pump Motor HP

Desired Pump Run Time

Tank Diaphragm Technology

⚡ Drawdown Gallons & Tank Sizing

Required Drawdown Volume -- Gallons delivered before pump starts

Minimum Tank Total Size -- Total internal tank volume

Air Pre-Charge Setting (Empty Tank) --

Boyle's Law Drawdown Factor --

Recommended Standard Tank Model --

Maximum Pump Cycles per Hour --

Pump Short-Cycling Risk --

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Why Water Well Pressure Tanks Are Necessary

Water is physically incompressible. If you connect a submersible well pump directly to plumbing pipes without a pressure tank, opening a faucet causes water pressure to drop to zero instantly. The pump would start immediately, run for 2 seconds to pressurize the pipe, and shut off—cycling on and off dozens of times every time someone washes their hands. This violent short-cycling overheats motor start windings, welds contactor relay contacts, and destroys a $2,500 submersible pump within months.

Boyle's Law and Usable Drawdown

A captive diaphragm tank contains a factory-pressurized air cushion separated from water by a butyl rubber bladder. Because air is compressible, it stores mechanical energy under pressure per Boyle's Law ((P_1 V_1 = P_2 V_2)). However, only a fraction of the tank's total volume is usable water:

Drawdown Factor = 1 - [ (P_cut_in + 14.7) / (P_cut_out + 14.7) ]
For 40/60 PSI: Factor = 1 - (54.7 / 74.7) = 0.308 (30.8% of tank volume)

A standard 44-gallon pressure tank delivers only 13.5 gallons of actual water between the 60 PSI shut-off and 40 PSI turn-on thresholds!

The Cardinal Rule: Pre-Charge 2 PSI Below Cut-In

To calibrate a pressure tank, shut off the pump breaker and drain all water from the tank until water pressure reads 0 PSI. Use a tire pressure gauge on the top Schrader valve:

30/50 PSI Switch: Pre-charge air to exactly 28 PSI.
40/60 PSI Switch: Pre-charge air to exactly 38 PSI.
50/70 PSI Switch: Pre-charge air to exactly 48 PSI.

If the air pre-charge is set equal to or higher than cut-in pressure, water will be completely exhausted before the pump switches on, causing a sudden momentary drop to 0 PSI (air spitting from faucets) before the pump kicks in.