What happens if a well pump is oversized?

Installing a 2 HP pump where a 1 HP pump is needed causes rapid short-cycling. The pump fills the pressure tank in 20 seconds and shuts off. Repeated frequent motor starts cause premature capacitor and winding burnout.

How do I determine my well's drawdown level?

The driller's well completion log records static water depth and pumping water level. If your well rests at 60 feet but drops to 120 feet while pumping 10 GPM, your drawdown is 60 feet and your pumping water level is 120 feet.

What size pressure tank do I need for a 10 GPM pump?

Submersible pump motors require at least 1 to 2 minutes of continuous run time per cycle to cool the windings. A 10 GPM pump needs a pressure tank with at least 10 to 15 gallons of usable water drawdown (typically a 32 to 44 gallon total volume pressure tank).

Free Submersible Well Pump TDH Calculator

💧 Well Depth & Water Elevation

Pumping Water Level Depth (ft) Static depth + well drawdown

Elevation from Well to House (ft) Vertical uphill grade

Desired Water Delivery Flow (GPM) Standard home: 8 - 12 GPM

Pressure Switch Cut-Off (PSI)

Drop Pipe Inside Diameter

Total Pipe Run Length (ft) Down well + horizontal ditch

📊 Total Dynamic Head & Pump Sizing

Total Dynamic Head (TDH) 287 Feet 124.2 PSI equivalent

Recommended Pump Size 1.0 HP 10 GPM series pump

Static Elevation Lift: 140 Feet

Pressure Tank Equivalent Head: 138.6 Feet (60 PSI)

Piping Friction Head Loss: 8.5 Feet (Low loss)

Minimum Pressure Tank Size: 32 to 44 Gallon Tank

✅ Equipment Matched: A 1.0 HP 10 GPM submersible pump will easily deliver 10 GPM against 287 ft TDH to shut off at 60 PSI.

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What is Total Dynamic Head (TDH)?

A deep well submersible pump does not merely lift water to ground level; it must push water all the way to the top of your house and pressurize a bladder pressure tank. Total Dynamic Head (TDH) is the sum of three distinct resistance forces expressed in feet of water:

TDH = Elevation_Lift (ft) + Pressure_Head (ft) + Friction_Loss (ft)

Converting PSI to Feet of Head

A column of pure water 2.31 feet tall produces exactly 1 PSI of hydrostatic pressure at its base. Therefore, to charge a 60 PSI pressure switch, the pump must produce: (60 ext{ PSI} imes 2.31 = mathbf{138.6 ext{ feet of head}}) purely to satisfy the pressure tank!

Why 1-1/4" Drop Pipe is Superior to 1" Pipe

Pumping 10 GPM through a 1-inch polyethylene drop pipe generates over 7.0 feet of friction loss per 100 feet of pipe. Upgrading to 1-1/4" pipe slashes friction loss down to only 1.8 feet per 100 feet (a 75% reduction), eliminating pump motor strain and saving significant electricity over the 15-year life of the pump.