A leaky foot-valve or check valve allows water to drain slowly down the well piping and flow back into the well. At some point, this will reduce the pressure in the pressure switch, causing the pump to cycle back on to increase the pressure. This is called intermittent pump cycling. It can drastically increase your electric bill and occurs when no water is being drawn from the system. Unfortunately, a leaky foot-valve or check-valve is not the only cause of intermittent cycling.
Determine the Cause of Intermittent Cycling
Eliminate all other leaks. A leak anywhere in the system can cause your pump to cycle intermittently. The key is to narrow down the location as much as possible. Start by closing the main valve to the house. The main valve is the one just beyond the pressure switch. This should eliminate all leaky toilets, sinks and household plumbing. If the pump still cycles, the leak is in the well, or the pipes between the well and the main valve.
Build a termination plug that will fit on the end of your pipe and have a pressure gauge. How you build this will vary depending on the type of pipe in your well. Basically it is just a series of pipe fittings connected together that will allow you to adapt from your pipe, seal off the end and terminate in a pressure gauge.
Build a clamp out of 2x4's. Bolt the two 2x4 boards together face to face with a piece of cardboard in between. Drill a hole the diameter of your pipe, down the center. Unbolt the 2x4s and remove the cardboard; there should be two crescent-shaped grooves: one on each board. Together, they will now be slightly smaller than the diameter of the pipe. This will allow you to clamp the well pipe without squashing it.
Flip the breaker at the circuit breaker panel to turn off the electricity to the well.
Remove the cover of the well housing. Often there is a series of eight or 10 bolts around the top. Once they have been removed, take the cover off.
Test the Well Pipe and House Feed Pipe
Attach the winch to the well pipe. There should be a gasketed flange attaching the well pipe to the sidewall. Pulling up on the flange with the winch will disconnect the pipe from the feed pipe to the house.
Pull the pipe up out of the well a couple of feet using your winch and clamp your 2x4s onto the pipe to prevent it from falling back into the well.
Verify that the clamp is holding the pipe by lowering the winch slightly. If it is holding, remove the flange from the top of the pipe and attach your termination plug and pressure gauge.
Pressurize the well pipe by turning the breaker to the well back on. It should hold the pressure for longer than an hour without cycling. If the pressure holds, your pipe and check-valve are not the problem. Check for leaks between the well and the house. If the pressure doesn't hold, the leak is in the well.
Winch the well the rest of the way out. If you determined the leak is in the well you have a leak in either the well pipe or a bad check valve. Either way, you should check both by pulling the pump out and pressure testing the separate sections of the pipe and the check valve.