How to replace a mechanical seal on your pool pump

One of the most common questions we get through the phone or through email is how to fix a leaky pump. The answer to that will of course depend on where the leak is located, but for leaks that happen in the middle of the pump or is located in the middle of the motor and the impeller (a dead giveaway is a leak coming from the vents of your motor) then it’s 99% that it’s a mechanical seal problem and you will need to replace it as soon as possible.

Now why do we need to replace it ASAP? Well, it’s simple. While your pool pump deals with water all the time, your pool pump water must be kept dry at all times! A leaky seal is actually a blessing in disguise, it gives you a tell-tale sign that maintenance is required. It’s better than a complete seal failure with no warning right? Spotting a pool leak or just evaporation? Click here for an in-depth guide to help you tell the difference.

Aside from opening up your pump and checking the mechanical seal manually, the best way to determine which mechanical seal to use is to get the part number from the user's manual. If you don't have your manual then don't worry, just shoot us an email at the contact form at the bottom with your pump brand and model and we'll sort out what seal is best for your pump.

Now, while it is technically possible to do all of the work poolside, Mr Pool Man always recommends that you have a worktable or workbench to do your work on. It takes a bit more time, but it saves you a lot of stress and makes the task so much easier.

The first thing you need to do is cut the power to the pool pump. Once you’ve shut the power off from the mains, disconnect the power connections from the pump. Close off all of the valves leading to and from the pump. Start by removing the motor. To do this, remove the bolts that hold the motor pump assembly to the wet assembly of the pump. See that red box in the photo above? That’s where the motor connects to the body. Once the screws are out, you can slide out the motor assembly and bring it over to your work table.

Once we’re comfortably at our work table, time to take the motor apart, well, not literally but you know what we mean. Remove the diffuser, this part should be straightforward. After taking off the diffuser, we need to take off the impeller. Now we can’t really twist off the impeller without securing the shaft so we will need to open up the back of the motor.

Remove the screws at the rear of the motor and pop off the cap, be sure not to touch the capacitor because it may still hold a charge and you might get a shock! Discharge the capacitor by using a screwdriver and shorting out the leads of the capacitor. While this is perfectly safe to do, please wear protective eyewear just in case.

Now, depending on your pump model, you may have to move aside the capacitor in order to gain access to the opposite end of the pump shaft. No need to remove the capacitor leads, just remove one of the screws holding it in place. Now that we have access to the pump shaft, secure it in place with a 7/16” wrench and turn the impeller counter clockwise.

Now that the impeller is off, we can now see the two parts of the mechanical seal. The white part should be attached to the seal plate while the black spring part is attached to the impeller. Remove the old mechanical seals by pushing them out with your hands. If they’re stuck, a rubber mallet can help, use something like the head of a screwdriver to push against the existing seal and give it a couple of gentle taps with a rubber mallet to pop them out.

Many people would just pop in the new mechanical seals, close it up and call it a day. But really, why rush? Since it’s already there, take a couple of minutes to inspect your impeller and clean it up properly. See if anything is stuck inside and for wear and tear. If you do spot any signs of damage, then make sure to note down your impeller model and order a replacement in advance, just in case.

Very Important: Wear gloves when handling the new seals. Oils from our hands (human body oils) can cause deterioration to the seals and may lead to premature damaging and leaking in the future. Did you take note of the way the seals were seated before popping them out? Well, if you didn’t, don’t worry! Here’s how they’re put together.

• Lubricate the white porcelain seal half on the rubber cup on the ceramic seat. Once that’s all nice and lubed up, gently push it into the seal plate, white side up. Set aside.
• For the other side, push the black spring seal into the pump impeller, with the black polished surface facing away from the impeller.

Once the mechanical seals are in, reattach the seal plate and the impeller. Again, secure the pump shaft with a 7/16” wrench then screw in the impeller clockwise. Don’t forget to re-secure the capacitor before closing up the back of the motor. Reassemble everything (don’t forget the diffuser!) and slide the motor assembly back into the pump body. Screw everything back in place, (don’t overtighten even if you’re tempted to do so! Overtightening can cause cracks which can lead to permanent damage) and reattach all of the electrical fittings. Once done, you can reopen the valves and that’s it! You’re done!

Sometimes a mechanical seal doesn't give you warnings and will fail on you causing catastrophic flooding of your pool pump motor. Now, you can always replace the motor itself, but we don't recommend that. A couple of reasons why we don't recommend simply replacing the motor when a a mechanical seal fails are the following:

• Replacement motors are pricey, they can run up to about half the price of a brand new pump.
• A sudden mechanical seal failure can also be a symptom of something else wrong in the pump (excess vibration and other problems) and it may happen again to your brand new motor.

In cases of mechanical seal failures causing motor failture, we recommend to simply replacing the whole pump itself, that way you'll be assured that the failure doesn't reoccur anytime soon, plus you'll have the peace of mind of a brand new warranty just in case. Browse our collection of pool pumps by clicking the button below.

BUT in cases where a pump simply dies or fails without a mechanical seal failure then a motor replacement can be a good option to go for.

Replacing a mechanical seal takes about 2 minutes and the part only costs a few dollars, what takes time is taking everything else apart. But this little maintenance trick will save you hundreds, if not thousands of dollars down the line so when you see your pump leaking near the middle or near the motor part, get yourself a new mechanical seal and fix it asap!

Related articles:

• Maintaining your Pool with a Broken Pool Pump
• Finding, Fixing and Preventing Spa Leaks, the only guide you’ll need