How To Replace a Pool Pump Impeller

Pool pumps aren’t cheap, so when yours stops running properly, you should understand how it works and determine whether you can fix the problem yourself to save yourself some money on the repair.

That’s the case with the impeller. If it breaks, you can replace it on your own. You just need to know how to do it.

What Does a Pool Pump Impeller Do?

The impeller is the most crucial part of the pump and its only moving part. It’s what pulls the water through the pump to circulate it, so without it, your pump is useless.

Older pool pumps may have semi-open-face impellers. However, today’s pumps have closed-face impellers, making them far more efficient but also a little harder to replace.

One of the most common problems with impellers is debris in the pump, and depending on what kind of debris it is, it can crack or break the impeller. In this case, when the rest of the pump is good, you just want to replace that part. If you just need to clean it, read my article on cleaning your pool pump impeller. Here’s a step-by-step guide to replacing your pool pump’s impeller.

Step 1: Cut the Power

You need to be sure your pump won’t turn on while you’re working, so make sure to unplug it. You could simply turn the switch off, but pumps have a bad habit of automatically turning themselves back on, and you don’t want that.

Step 2: Open the Relief Valve

After you’ve unplugged it, open the relief valve to let out all the pressure inside the pump. It will spray at first, so be prepared and don’t get a face full of water. Wait until the gauge reads 0 psi before doing anything else, even after the water stops spraying.

Step 3: Remove Fasteners

Remove the bolts and washers that attach the motor assembly to its housing, and keep track of them as you remove them. Put them somewhere you won’t lose them, like a small container or snack baggie. That way, when it’s time to reassemble the pump, you have all your fasteners.

Step 4: Remove the Housing

Gently pull the motor assembly free of the housing and set the housing aside and out of your way.

Step 5: Check and Remove the Diffuser and Gasket

The pump’s diffuser and gasket are located at the end of the assembly. Snap it off and check both pieces over before setting them aside (This is an excellent time to check them over and see if they need replacing as well).

Note: Sometimes, the diffuser gets stuck in the housing. If it’s not on the end of the motor assembly, check inside the housing. Pull it out from there and check it over.

Step 6: Secure the Motor Shaft and Remove the Impeller

You have to unscrew the impeller from the motor shaft, which means you need access to the shaft to hold it in place.

Remove the Cover and Capacitor

To do that, go to the other end of the assembly and take the back cover off. You’ll see the motor’s wiring, capacitor, and a plastic strip between its leads to prevent shorting.

Since the capacitor stores power and you have to pull that plastic strip out, you need to carefully place a screwdriver across its leads to temporarily short it out and avoid getting a shock.

Then remove its screw, take it off its leads and push it out of the way. You don’t need to disconnect it.

Holding the Shaft and Removing the Impeller

Use a wrench or a pair of pliers to hold the back end of the motor shaft steady, and turn the impeller counterclockwise to unscrew it from the shaft. You might have to use a strap wrench or something else soft to loosen it at first. If you’re having trouble, read my guide on removing a stuck pool pump impeller.

Step 7: Remove the Seal on the Impeller

The impeller has a seal on it. Half of that seal is in the seal plate on the end of the motor shaft, and the other half is on the end of the impeller. Remove the part that’s on the impeller, paying close attention to how it’s mounted.

Step 8: Put The Seal On the New Impeller

Unless you need to replace the seal, you can use the old seal on the new impeller (you should probably do this anyway because using the seal that comes with the new impeller can cause headaches due to a poor fit).

That’s why you need to pay attention to how it sat on the old impeller. You need to put it on the new impeller with the same orientation so it’ll go back onto the motor shaft properly.

Avoid touching the bearing on the top of the seal because the oils from your skin can corrode it.

Step 9: Reassemble Your Pump

Now that your new impeller is ready screw it back onto the motor shaft, making sure that the seal seats itself properly on its other half. You can hand-tighten it; no need to torque it down.

Put the capacitor back into the pump’s motor assembly and reattach it to its leads, put the plastic strip back into place, and then reattach the assembly’s back cover.

Lubricate the diffuser’s gasket (if you don’t have to replace the diffuser) and put the diffuser back onto the assembly. Slide the whole thing back into its housing and secure everything with the bolts and washers you set aside earlier.

Step 10: Prime the Pump

Remove the lid on the strainer and fill the strainer with water. Then put the lid back on.

Step 11: Plug the Pump Back In

Plug the pool pump back in and turn it on. If you cut power by turning off the circuit breaker first, remember to turn the breaker back on as well.

Once the pump is running, wait for the water to start spraying out of the relief valve and close it.

Congratulations! You’ve just replaced your pool pump’s impeller all by yourself and probably saved a bundle over an entirely new pump.

Questions about replacing the impeller? Drop me a line.

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