A leak in your pool filter could be something small, or it could be a really big thing. Either way, it needs to be repaired. Here are some things to look at in the process of diagnosing your pool filter leak.
If your filter body is cracked then it is definitely time for a new filter, especially if your filter is over 5 years old. On some filters, you can find a new tank half, but it is usually very expensive (at least half the cost of the filter) and it is a gamble. If the filter is old enough that one half has cracked, how long will it be until the other half also cracks? And then there are other things that can go wrong also.
If you have a cracked tank, it is almost always best to go ahead and replace the entire filter. The only exception would be perhaps on a filter that is only a few years old and where the problem was not a product of old age of the tank.
If the filter is leaking at the bulkhead fittings (these are the fittings that the backwash valve attaches to), then you have a couple of possible solutions.
If the bulkhead fitting has a nut inside the tank, then the filter will have to be taken apart and gaskets replaced, and the nuts tightened.
If your bulkhead fitting threads into the tank itself, you may be able to just tighten the fitting from the outside and fix the leak. If that does not work, you will need to get new o-rings, but you can probably still fix it without completely disassembling the filter.
If the filter is leaking at the center where the two halves come together, then the filter needs to be taken apart and serviced. Here is what should be done whenever you take the filter apart.
If your filter leaks after this, then check carefully for a hairline crack around the flange of the tank half. If you have a crack, then the filter will need to be replaced.
On some older stainless steel tanks, the sealing surfaces can become corroded and unable to seal. In this case, the filter also should be replaced.
Air relief assembly– sometimes these can leak either on the assembly themselves or on the o-ring where it seals to the tank. We have seen where a air relief assembly sent a slight drip down the back of the filter onto the center clamp making it look like the center o-ring was leaking.
Drain plug– if there is a leak under the filter, it might just be a drain plug. You will need a flashlight and a mirror to inspect this.