Water Well Submersible Pump Installation: The Right Way to Do It


A submersible pump sits fully submerged at the bottom of your well casing, pushing water up through a drop pipe to your pressure tank and distribution system. Unlike jet pumps, submersible pumps are silent, self-priming, and efficient – but installing one incorrectly causes premature motor failure, waterlogged pressure tanks, and contaminated water. This guide covers every stage of a correct pump installation, from selecting the right unit to lowering it safely into the well.

Key Takeaways

– Size the pump to your well’s recovery rate, not just your household demand – a pump that outpaces recovery will run dry and burn out within months.

– Use a torque arrestor if your well casing is 4" or smaller; motor start/stop torque causes the pump to swing and abrade the drop cable against the casing wall.

– Install a check valve within 25 feet of the pump outlet, and a second one at the pressure tank inlet if the vertical rise exceeds 50 feet.

– Minimum wire gauge for a 1 HP, 230V pump at 200-foot depth is #10 AWG – undersized drop cable causes voltage drop that overheats the motor.

– A waterlogged pressure tank (pre-charge below 2 PSI under cut-in pressure) forces the pump to short-cycle, which is the leading cause of motor winding failure.

What Is a Submersible Well Pump?

A submersible pump is a sealed motor-and-pump unit designed to operate underwater. The motor is hermetically sealed and cooled by the water surrounding it. Water enters through intake screens near the bottom, passes through one or more impeller stages, and exits through the drop pipe rising to the surface.

Most residential well pumps are 4" diameter units rated between 5 and 25 GPM. A 10 GPM pump is adequate for most single-family homes with a well that recovers at least 1 gallon per minute. For wells with slow recovery, match pump GPM to the recovery rate, not the peak demand.

Parts You Need Before You Start

Step-by-Step Pump Installation

Step 1: Measure Well Depth and Static Water Level

Lower a weighted tape or electronic sounder to confirm total well depth and current static water level. The pump should be set 10-20 feet above the well bottom to avoid drawing sediment, and at least 10 feet below the static water level to prevent air entrainment.

Step 2: Assemble the Drop Pipe, Cable, and Safety Rope

Attach the drop pipe to the pump outlet using a brass fitting – never plastic threads directly on the pump. Tape the drop cable to the drop pipe every 10 feet using electrical tape or cable ties rated for submersion. Attach the safety rope to the pump’s lifting eye with a stainless steel clamp, not a knot that can slip under load.

Run the drop cable alongside the pipe, not wrapped around it. Wrapping creates stress points that crack insulation over time.

Step 3: Install the Torque Arrestor

Slide the torque arrestor onto the drop pipe just above the pump before lowering. It expands against the well casing wall and absorbs the rotational force when the motor starts. Skipping this step in a tight casing is one of the most common causes of drop cable damage and early pump failure.

Step 4: Install the First Check Valve

Thread a check valve into the pump outlet or into the drop pipe within 25 feet of the pump. This prevents water from draining back down when the pump stops, which would cause the pump to restart under full column pressure – a condition that stresses motor windings and impeller seals.

For well-water projects, verify casing diameter, static water level, flow demand, and cable length against Mislier submersible well pump options before ordering equipment.

Step 5: Lower the Pump Using a Pitless Adaptor Tool

A pitless adaptor allows the drop pipe to exit the well casing horizontally below the frost line without breaking the sealed bore cap. To lower the pump, you need a homemade or commercial lifting tool – typically a 6-foot length of 11/4" threaded steel pipe with a tee handle – that threads into the pitless adaptor and supports the assembly while you feed pipe sections down the casing.

Lower slowly. Never let the drop pipe fall free or bounce against the casing. Have a second person manage the drop cable and safety rope to prevent tangling.

Step 6: Secure the Bore Cap and Pitless Adaptor

Once the pump is at the correct depth, seat the pitless adaptor into its receiver fitting in the casing wall. The bore cap seals the top of the casing against insects, surface water, and debris. A compromised bore cap is a direct contamination path – inspect the seal and replace it if cracked.

Step 7: Wire the Pump

Run the drop cable from the well head to the pressure switch and control box (for 3-wire pumps) or directly to the switch (for 2-wire pumps). Use waterproof wire connectors rated for direct burial at the well head junction. Confirm wire gauge against depth and HP:

Undersized wire causes resistive heating that degrades motor insulation over years, not days – the failure looks like a random motor burnout.

Step 8: Connect the Pressure Tank and Pressure Switch

Set the tank pre-charge pressure to 2 PSI below the cut-in pressure of your pressure switch. For a 30/50 switch, pre-charge to 28 PSI. For a 40/60 switch, pre-charge to 38 PSI. Check pre-charge with a tire gauge when the tank is empty and the system is depressurized.

Install a second check valve between the pump outlet line and the pressure tank if your vertical rise exceeds 50 feet. This prevents water hammer when the pump cycles off.

Step 9: Prime, Test, and Inspect

Restore power and let the pump fill the system. Watch the pressure gauge – it should rise steadily to cut-out pressure (50 or 60 PSI) and hold. If pressure bleeds down with no fixtures open, you have a check valve failure or a leak in the drop pipe joint.

Run water for 5 minutes and check for sediment or discoloration. New installations often flush fine sand from the well screen. If discoloration persists beyond 10 minutes, the pump intake may be too close to the well bottom.

Common Mistakes That Cause Early Failure

– Oversizing the pump: A 25 GPM pump in a well that recovers at 3 GPM will run the well dry within minutes. Match GPM to recovery rate.

– Skipping the torque arrestor: In a 4" casing, the pump swings on every start cycle. The drop cable abrades against the casing wall and eventually shorts.

– Waterlogged pressure tank: If the bladder fails or pre-charge drops, the pump short-cycles – sometimes 10-20 times per hour. Motor windings fail from heat, not age.

– Improper wire splices: Any splice in the drop cable must use waterproof heat-shrink connectors rated for submersion. Standard wire nuts wick moisture and corrode within a season.

FAQs

How many GPM does a residential well pump need?

Most single-family homes need 6-12 GPM at peak demand. The limiting factor is usually well recovery rate, not household demand. If your well recovers at 2 GPM, a 10 GPM pump will exhaust the well in minutes. Size to recovery rate first, then confirm the pump can meet peak demand with a storage tank buffer if needed.

Can a pressure tank be too large for the pump?

A larger tank is almost never a problem – it reduces pump cycle frequency and extends motor life. The risk runs the other way: an undersized tank causes short-cycling. The practical minimum is 1 gallon of drawdown capacity per 1 GPM of pump output. A 10 GPM pump needs at least a 20-gallon tank (which provides roughly 5-7 gallons of drawdown).

What is the difference between a 2-wire and 3-wire submersible pump?

A 2-wire pump has its start capacitor built into the motor housing. A 3-wire pump uses an external control box that houses the start and run capacitors. The 3-wire design is easier to service – you replace the control box above ground rather than pulling the pump. For depths over 200 feet or pumps over 1 HP, 3-wire is the more serviceable choice.

Does a submersible well pump need a check valve if the pressure tank is close to the well?

Yes. The check valve protects the pump from water hammer and prevents back-spin of the impellers when the pump stops. Distance to the pressure tank is not the relevant variable – vertical head is. Any installation with more than a few feet of vertical rise needs a check valve at the pump outlet.

Conclusion

A correct water well submersible pump installation comes down to four decisions made before the pump goes in the ground: matching pump GPM to well recovery rate, sizing the drop cable for depth and load, installing check valves at the right points, and setting pressure tank pre-charge correctly. Get those four right and the pump will run for 15-25 years. Get any one wrong and you will be pulling the pump again within a few seasons.

Before your next installation or replacement, verify your well’s current recovery rate with a drawdown test – not the original driller’s log, which may be decades old and no longer accurate.