Why Is My Pool Filter Leaking? (Common Problems)

Why Is My Pool Filter Leaking?

There is plenty of pool equipment to worry about in terms of troubleshooting to locate a water leak. A salt water pool has several extra components including a salt cell, water flow sensor and the salt chlorination system itself that you need to worry about.

Sometimes, locating a leak in the pool equipment area can be more difficult if the equipment is sitting on grass or gravel and the leak isn’t easily able to spot.

A leak in your salt water pool filtration system usually comes from the filter housing itself from a gasket or loose clamp. A pressure gauge or valve that hasn’t been properly tightened can also be the culprit as the vibrations from the pump can loosen clamps and fittings over time.

Why is my pool filter leaking?

Here are the most common reasons your pool filter is leaking and what you can do to troubleshoot it yourself and make the fix.

Pool filter leakage problems on the filter itself

There are a number of common reasons your pool filtration system can leak in around the filter unit itself. Here are the main ones:

Gasket leak

If you take the filter housing apart and put it back together again improperly, the gasket can get pinched when reattaching it. This can easily lead to a leak especially if you damage or rip the gasket as you seat the top of the filter housing in place again.

If water is dripping from around the part of the filter where it’s attached, check to see if the gasket itself has a problem. Over time the gasket may need to be replaced if it cracks or hardens and rips.

Clamp leak

On sand filters and certain types of cartridge filters, the top of the housing is held in place with a metal clamp that tightens and creates a seal to help retain the pressure that builds in the filter when the pump is turned on. If the clamp is incorrectly applied or isn’t tight enough, water can leak out and reduce filter efficiency.

If you have a filtration system with a clamp assembly that includes multiple clamps that are manually tightened around the filter housing such as a Sta-Rite system, one or more clamps can either be incorrectly positioned or over time, can loosen due to the vibrations when the pump is running. Either situation can cause water to leak slowly or drip from the housing.

In my experience with the Sta-Rite system the brackets can sometimes be slightly difficult to grab onto the housing exactly so care needs to be taken. Over time, I have checked brackets and had to retighten them as they had come loose over a few weeks time.

Drain valve leak

Pool filters have some sort of drain plug or valve to allow water to flow from the filter housing and also for washing the filter out from time to time. Typically it’s on the side of the filtration housing or near the bottom of the tank.

On our Sta-Rite System 3 filtration system, there is a drain plug that screws on at the bottom of the housing of the filter housing itself. It has a diameter of about 2″ give or take and can be used not only to drain the filter at the end of the season but also to wash out the cartridges and to rinse out sand that accumulates at the bottom of the housing.

If you damage the small O-Ring or fail to tighten the plug properly after taking it apart, it will leak. It can be easily tightened with an adjustable wrench or screw driver depending on the model you have but you do need to ensure it isn’t cross-threaded or left loose.

Pressure gauge leak

The pressure gauge is usually located right at the top of the filter housing and as the name would suggest provides a pressure reading of the filter unit when the pump is running. In winter at closing, the gauge is typically unscrewed and brought in for the winter.

The pressure gauge has a small gasket and small threading on it so it can be easy to damage it over time typically through over tightening when screwing it back onto the top of the filter housing or through cross threading.

The gauge also typically has a small air valve that opens and closes to allow air to escape from the filter when you start the pump up and are clearing the air out after washing the filtration system or otherwise taking it apart. Once the air has been removed from the filter, a small stream of water starts to come out and you can then close the valve. If you fail to properly tighten the valve, it will leak.

Filter crack

The filter housing itself can crack and that can most certainly cause a leak. Depending on the size and location of the leak, a PVC epoxy resin or glue can typically be used to repair the crack.

If the crack is large enough or has dented the housing you might need to replace the filter housing especially if it’s of a good age and if you can’t get the dented part pushed back into alignment. The filtration system builds up pressure when the pump is running and maintains this pressure as it operates so the housing needs to be tightly closed and airtight during operation.

Pool filter leakage problems on the filter itself
Pool equipment that is packed tightly together (and sitting over grass or gravel to boot) can make it difficult to see a leak let alone to quickly determine where it’s coming from specifically.

Pipe leakage problems around the pool filter

If you check out the picture above, you can see a significant amount of pool equipment including (from left to right) a heater (green box), electrical box, piping, filtration system, more pipes, pump, lots more piping and more equipment. It can be difficult to quickly diagnose a leak sometimes and more so if the equipment is located over gravel or grass which can hide the dripping water better than if the equipment was located on top of bricks or concrete.

Here are some common reasons why a pool filter can leak in and around the pool filter unit.

Piping leak

Check the PVC piping in and out of the filter system as over time the seals can weaken and leak. You can typically repair minor leaks yourself by applying a PVC cement or glue to fix it. It has happened several times to me over the years but for the most part, the piping has held up well.

Pool heater system

The pool heater system also has piping coming in and out of it and if it’s located close enough to the filtration system, you might mistake a leak from the heater as actually coming from the filter. Pool heaters can also leak from underneath.

Having said that, a pool heater “leak” can also be condensation that isn’t harmful.


If your pool equipment is situated fairly close together, it can sometimes be difficult to determine exactly where the leak is coming from. Pool leakage can also occur in around the pump, from the pump basket, the heater, the piping leading in and out of the heater and in and around the salt call among other place.

Carl Mueller

I bought a home with a salt water pool in 2006 and soon realized the benefits over traditional chlorinated pools. On this website I'll discuss all the tips and tricks I've learned over the years. I'll also help you troubleshoot various problems with pools in general and ones specific to salt water pools that I've experienced personally!

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