Introduction: Diagnose and Replace a Submersible Well Pump

About: Photography teacher, woodworker, and general repair man

So, the other day I noticed that my well pump was running, A LOT. If you want to search the symptoms, it's called "short cycling" and is absolutely horrible for your pump. Short cycling is when your pump runs, pressurizes your tank, and then immediately runs again. This leads to overheating and failure.

To me, this seemed like a simple thing to fix because I knew that my pressure tank was way past it's warranty (it's 25 years old) so I assumed that it was that. It turns out that my pressure tank is fine but that it's too small. This over worked my pump to the point of failure.

This instructible covers my process to diagnose and remedy the problem. It is also directed at 2-wire systems, not 3-wire systems. If you have a control box, you have a 3-wire pump. If you don't have a control box, you have a 2-wire pump.

Super important note: My well is only 50ft deep and my pump is only 20ft down the hole. This makes my process very easy. Some states maintain a record with the DNR of well depths which you can find by typing "*State Name* DNR well records" into Google. Here is Indiana's. Fun fact, nothing creeps your neighbor out more than knowing when, how deep, what their pump depth is, and who drilled their well.

Also, you should have stickers somewhere that tell you what kind of pump you have and when it was installed. I used this and the pressure tank's draw down levels (available at the manufacturer's website) to calculate how long my pump should be running and then checked it against what it was actually doing. It's also good to know how old your pump is so you can plan for failures.


First, let's go over what I don't have. I don't have a license in electrical, plumbing, or wells. I also don't have $4000+ to hire a pro. What I do have is a shallow water table, tools, and access to the internet.

In other words, if you're reading this, you're reading the ramblings of a just a random guy who has done it once who happened to read a lot of tutorials and watch some Youtube videos on well systems. I'm not an expert by any means and I encourage you to consult a professional.

As always, please work safely. Shut off the power at the breaker and the switch before working on your well because most run on 220v or 230v. You will get wet, you will be standing on the ground, and those voltages can kill you.


Second, if your pump has failed it is crucially important to understand why. A quality pump should last 10-20 years from my readings and personal experience. Mine failed after six years. Simply replacing the pump with a new one without investigating why it failed will likely lead to the new one failing in six years.

When I bought my home, the sellers had to install a new well pump because the old one was not supplying enough pressure. They did that but never changed the pressure tank. The new pump needed a much larger pressure tank than what was left in my home.This caused my pump to run three times as often as it should and not long enough to cool, leading to a drastically shortened lifespan.


Third, any time you open your well head, you're going to want to sanitize the well. It's a gross place that can breed bacteria which can make you sick. I have a step specifically covering that.


Fourth, again, attempt this project at your own risk. It really isn't that difficult but I can see how it can become incredibly difficult really fast. It isn't that costly given the parts but if something goes wrong, I bet that it can become incredibly expensive. Realistically, you should probably not listen to my advice and just hire a professional.


Step 1: Diagnose the Issue - Water Pressure Tank

As I said earlier, replacing the pump without finding out why it failed is a bad idea. You will inevitably end up replacing your pump again in the near future. So, let's diagnose the issue.

There are basically three parts to a well water system. A pump, pressure tank, and electricity.

Pressure tanks commonly last 10 years or less. Mine is 25 years old so I immediately assumed that was the problem. Testing a pressure tank is pretty easy.

Regardless of these tank pressure tests, you want your pump to run at least 1 minute if it the motor is under 1hp and 2 minutes if it is over 1hp. My tank was just fine but my motor only ran for 15-20 seconds to get a full pressure load. This is what lead to the premature failure.

You can estimate the run time by using your gallons per minute rating of your pump. Mine is 10gpm and 1/2 horsepower so I need a 10 gallon DRAW DOWN reservoir in my pressure tank. A 20 gallon pressure tank has only only between 4-6 gallons of water draw down so I need a 50 gallon or more tank.

In addition to this, the depth of your pump, and pressure of the system also play a role in this calculation. The more pressure that you have, the lower the draw down volume is meaning that you could get away with a smaller tank (probably not advisable). Pump depth is also important. The deeper the pump, the less effective it is at pumping water so a 10gpm pump at 200 ft. deep may only be pumping 8gpm. That isn't as big of a problem compared to when that same pump which is rated for 150 ft deep is only 20ft deep. When it is far more shallow it doesn't have to move as much weight of water making it more efficient. For instance, my pump is pumping closer to 18gpm (pumps roughly 6 gallons in 20 seconds currently) so I need a much larger tank. My new pump pumps 16 gallons into the pressure tank in 64 seconds.


Step 1: find the little air valve. It's somewhere on or near the top of the tank.

Step 2a: Release some air from the valve. Did water spray out? If yes, your pressure tank is waterlogged. Supposedly you can just pump the water out by draining the pressure from your lines and filling it with air; however, if it were mine, I'd just replace it because it's obviously bad. I suppose pumping it could give you a few days of time so that you could complete the repairs on your own schedule.

Step 2b: Air came out. Shut the water off to your home BEHIND the pressure tank then drain all of your lines. Then, take a pressure reading at that valve. It should be a few PSI below your pressure switch's "on" setting. For me, my pressure switch kicks on at 30 PSI so I want my tank to read 27 PSI when it's fully empty. Mine read 22 PSI so I pumped it up until it was at 27 PSI. That didn't fix the problem but I felt good about it.

If your pressure tank is set to be over your pressure switch's cut-on level, your pump will run prematurely and shut off after only a few seconds once it reaches the cut-off level. In that instance, you want to bleed some pressure out of your tank.

Is your problem fixed? If yes, Yay! If not, continue on.

Step 3: Check the check valve on your pump. With your pressure tank fully pressurized, shut the water off AFTER the tank. This will leave only your tank and pump connected together. Does pressure remain constant for 10+ minutes? If yes, something is happening with your motor to cause it to short cycle. If the pressure drops, you have a bad check valve which is causing your pump to work extra hard (turn on too often/start while moving in reverse) and draining your lines which causes your pump to run.

Step 2: Diagnose the Issue - Well Pump and Electricity

This is a little more involved and basically only covers 2-wire setups. I used this document to find all of the electrical values. It also has instructions on how to test both 2 and 3-wire pumps. It's a terrific resource but it only applies to Franklin pumps.There should be a sticker near your inlet or in your control box to let you know the model number and manufacturer of your pump.

Step 4: Check the line voltage. This is pretty simple. Take the cover off your pressure switch and check the voltage between the two screws for each leg (assuming you have a 2-wire pump). For me, I know that each side should read 115v, which it does. If it didn't, my problem would be in the electrical wiring TO the pump (blown fuse most likely). Since mine did read 115v on each leg, I moved on to step 4.

Step 5: Check the resistance between the legs. Disconnect the pump from the pressure switch. Take a resistance reading between the two wires. My pump is supposed to read 4.2-5.2 ohms. Mine was 4.5 ohms. If your pump is within it resistance readings, move to step 5.

If the meter reads OL, then a wire is physically broken somewhere, find it and replace it. This could be due to the pump twisting in the pipe and breaking the wire. If that is the case, put in a torque arrestor. They're only $16 and will save you the headache of this happening again. Replace the wire with submersible grade wire.

If the meter is reading less resistance than what it should, then you have a short inside the motor. It's going bad and needs to be repaired or replaced. Move on to Step 3 of this instructible (next page).

Step 6: Measure the current. You'll want to do this on the start up and run. Start by turning power to your pressure switch off. Then, drain enough water that your pressure switch will turn on. Then, disconnect a black wire from your pressure switch. With your meter in its 10a setting, connect one lead to the black wire and the other to where it was connected to your pressure switch. Then, turn the power to your pump back on.

On my 2-wire pump, I should have a constant 5 amps. Instead, I have a start of 20 amps and then it decreases to 16 amps before turning off. This means that my pump is working extra hard to move water which indicates a bad impeller, bearing, line blockage, or bad check valve.

Step 7: Check the check valve. To do this, you must pull the submersible well pump. I cover that in the next section.

That said, well pumps sometimes have check valves. If it's bad, it won't close allowing water to drain through the impeller. This causes it to spin in reverse while it's off so the motor has to work extra hard to get the water moving in the correct direction. A bad check valve can also not allow water to move out of the pump causing excessive loads on the motor.

Step 3: Remove the Submersible Well Pump

If you have made it this far, I feel your pain. You're dreading the cost of a plumber/well tech. You're thinking, "how hard can this be, it's a pump on a pipe in a hole?" And, depending on where you live, you're both not wrong and incredibly wrong.

I am lucky to live in an area where the water table is 10-15 ft. down. In fact, now that I know that, I fully understand why the entrance to my neighborhood is constantly flooding. Other places need to drill 300+ ft down to get to an aquifer.

This is where things get a little dicey. If you break your well pump off, it's going to fall into a very narrow hole. You're going to want someone to hold the rope for you. If you don't have a rope attached to your pump, put one on. They're very inexpensive but could save you thousands.

Remember how I said that I'm not a well technician? What I am about to say comes purely from the internet. You could research it on your own. Better yet, call a professional.

Note: There's a photo of the T with an arrow on it. This arrow lines up with a notch in the PVC. It points to where the pipe that feeds into your house connects to the well pipe. You'll need to line that up when you put your pump back in place.

Step 1: Identify your pitless adapter type. Your adapter is probably 5ft down so you can get a good look at it with a flash light. This is important because they all require different tools, or no tools, to get to release. There are a ton of Youtube videos showing these.

If you don't have a T at the top of your well, and you can see that nothing is on the back side of the adapter, you will need a pitless adapter wrench. Google it, it's basically $20 in 1" piping that you screw into the top and then just yank. You make a 5ft T, thread it into the top of the adapter, and pull it off its cleat.

Now, just because you don't have a T at the the top doesn't mean that there isn't a nut down there that needs to be turned. If something is on the backside of the adapter, there is likely some sort of nut which will release the cam. (I only came across one photo of this so I assume it is extremely old and/or rare)

If you have a T like mine at the top, you will need a wrench that's 5ft long. I tried making a screwdriver out of rebar like all the tutorials said and it didn't have enough rigidity to turn the screw so I went with the wrench. To make the wrench, get a 1/2" x 5ft piece of gas pipe (mine is 10ft because I had it laying around) and bang the end flat so that it is roughly 3/8" on the inside. Then, slide that pip down the center hole. Twist counter clockwise until it seats itself. Continue turning until you hear rushing water. Once the water is done draining from your home, continue to turn the screw until the pump moves freely (pull up on the pump every now and then, when it moves freely, you have loosened it enough).

If the pipe gets stuck, don't worry. Just keep unscrewing until the whole screw comes out. Then, cut the end with the stuck screw off and bag it flatter so that the flat part of the nut can easily slide out the back side. Reshape the new end of your pipe and gently thread the screw back in place. Do this while it is out of the well so that you don't inadvertently damage the threads by dropping it down a 5ft hole.

Note: Don't be an idiot and pull your pump if it is not moving. This gets expensive once you break something. If it seems stuck, call a pro.

Step 2: Pull the pump. Start by disconnecting the wires at the top. Have one person hold onto the rope and guide the tubing that is coming out of the hole. The other person pulls the plumbing out of the pipe. Eventually, you will have a length of piping, pitless adapter valve, and the pump laying in your yard.

Step 3: Disconnect the pump from the main pipe. It's pretty simply, cut the tape holding the wire against the pipe, unscrew the pump.

Step 3a: If you had a leaking check valve as possibly diagnosed earlier AND your electrical readings are all where they should be, you MAY be able to get away with putting a check valve between the pump and the pipe. Doing that solved some of my problems (mine was bad and couldn't charge my tank more than 10 PSI) but did not fix the motor burning out.

Step 4: Replace the Submersible Well Pump

At this point in my journey, it was 1am, and 7 degrees outside with a decent wind blowing. I'm fairly certain that well pumps are designed to fail at the exact worst possible time. I took fewer photos because I was cold and wet even though I was working inside a garage for much of this part.

Step 1: Replace the motor and piping. If you need to add a torque arrestor, now is the time to do it. Then, put your new pump on by threading it into place. Remember to add a rope to be able to help pull it out of the hole next time. Reassemble the well piping and pitless adapter. With your new pump secured in place on the pipe, it's time to wire it up.

Step 2: Wire it together. Start by putting your shrink tubing on first. Then, add your crimps. Mash the ends together really well because you don't want them coming loose. Use a flame or heat gun to shrink the tubing. Start from the middle and work your way out. This will help remove any of the air in the tubing. Glue should be coming out of both ends and all the way around the wire. Remember, this will be submerged in water so you want to do this right. Tape that mess to the pipe.

Periodically tape the wire to the side of the pipe.

Step 3: Put it back in the hole. Finally, attach a new rope to your pump. I wiped my pump down with bleach as I put it back in the hole. It seemed like a good idea because I had leaves stuck to the pipe and this removed and sanitized the pipe. (the sanitizing process will sanitize your pipes as well)

Remember that photo of the T with an arrow on it? The arrow lines up with a notch in the PVC. It points to where the pipe that feeds into your house connects to the well pipe. You'll need to line that up. With everything in line, use your wrench to tighten the bolt and secure the pitless adapter. Wire it back up using heat shrink tubing where needed and reinforcing all wire nuts with electrical tape.

Step 5: Bleach Your Well

Any time you take the well head off your well, you need to bleach the whole thing. To do that, you need to work out how many gallons of water are in your well.

I'm going to give you a link rather than retype the words. I don't want to be responsible for someone getting sick.

Disinfect your well:

This is incredibly important. DO NOT SKIP THIS STEP!!!

Once you have bleached and circulated the pump, put the well head back on.

When you go to drain the chlorinated lines, do not do it in your sink. Run a hose outside, away from lakes, rivers, streams, etc. Pumping a gallon or so of bleach into your septic all at once will cause problems.

Step 6: Done

That's basically it. If you know what's wrong, replacing a well pump can take as little as an hour plus the bleach time. Replacing the pressure tank should be another hour or so. For me, the biggest issue was diagnosing the problem.

I hope this instructible helps you or at least aids in the diagnostics of a flaky pump. If you feel like you are in too deep, please call a professional. I'm just a random guy and am not responsible for you breaking your well, pump, pressure tank, or plumbing because you read this.