Hot Tub Filter Leak Repair

Hot tub filters need some repair from time to time, besides replacing the cartridge. Common hot tub filter leaks can include cracked filter housings, leaking o-rings or gaskets, or pipe fittings that have shrunken or otherwise lost their seal where the pipes connect.

There are three main types of hot tub cartridge filters: the skimmer filter, the inline filter and the top load filter...

Skimmer Filter Leaks

The usual problem with a skimmer filter is leaking around the filter housing. If the spa skimmer is leaking where the skimmer connects to the backside of the spa shell, you can seal it up with silicone or replace the square gasket that fits between the skim-filter and the spa shell. In either case, lower the water level below the skimmer by draining. A new spa skimmer gasket will be the best leak repair option, just remove the front cover plate to access the screws. Use a large #3 Phillips head to get the screws really tight, without damaging the heads.

Skimmer filters that have cracks in the filter housing or cartridge canister have a different problem. This is usually caused by freeze damage, from water freezing inside of the hot tub filter housing. Small cracks on skim-filters can be successfully repaired with a two-part epoxy sealant, or heavy duty silicone - if the crack is small enough. If the entire bottom of the filter canister cracked, it may be wise to repair the entire skim filter assembly, or at least the canister portion of the skim-filter.

Skimmer filters for spas also have a few other parts to keep them in working order. Over time, you may need to replace the skimmer basket or weir (the flapper door thingy). Some spa skimmers have a floating weir, or may have small clips and seals or adapters that need to be in place for proper operation.

Leaking Pipes? The piece that connects to the bottom of your skimmer filter may be a threaded fitting (aka spigot or MPT), or it may be smooth pipe (aka socket or slip). If either begin to leak water, you can repair it two ways. First, lower the spa water to a point below the skimmer bottom. If you can access the inside of the skimmer with a small tube of high temp silicone, you can place a thick bead on the inside, where the fitting connects to the port. If you can't reach it, you can try sealing the outside of the fitting, while running the pump, to suck the sealant into the void. Not always a permanent repair however.

Inline Filter Leaks

An inline filter is one that is not a combination skim-filter, but a separate filter assembly that is plumbed 'in-line', or attached to the pipe. In some cases, the inline spa filter is plumbed in place before the pump, although in most cases it is connected after the pump (and before the heater).

For a spa filter that is attached before the pump, cracks or loose filter parts can cause the pump to pull air into the system. When installed after the pump, the filter housing is under pressure and any crack or loose parts (like the lock-ring) will cause the pressurized filter body to leak water when the pump is on. In either case, the filter will leak water while the pump is off, since it's installed below the water level.

A leaking spa filter housing (aka canister or body) cannot usually be successfully repaired for pressurized spa filters. The best repair is to replace the filter housing body or replace the entire filter assembly, which includes a new cartridge. A new complete spa filter will also include a new top assembly and bypass valve, to allow water to bypass the filter when the pump is running on high speed.

Small cracks on a hot tub filter housing that is installed before the pump (under suction) may be successfully repaired with an effective two-part resin-hardener type of epoxy sealant. For large cracks however, the best repair is to replace the spa filter housing or canister, or the complete filter.

Many times however, an inline spa filter may not be cracked, but leaks where the filter body attaches to the filter lid, via the round lock ring. A cracked lock-ring can cause this problem, as can a loose lock ring. Before you go hammering on the lock ring however, they are designed to require only hand-tightening. Over-tightening the spa filter lock ring can cause it to crack, so proceed carefully. In most cases, replacing the filter canister o-ring, and lubricating it with a proper o-ring lube will solve this problem.

Top Load Filter Leaks

Top Load filters are accessed while in the spa, or standing outside the spa - no need to climb into the equipment bay to check the filter, although they can also be installed underneath, inside the cabinet. Top Load filters have the plumbing connections at the bottom of the filter housing or body, while the inline filters (shown above) have the pipe or hose connecting through the lid, at the top of the filter assembly.

If a Top Load filter is leaking from the lid, a new o-ring is the usual solution, properly lubed with a lubricant specifically designed for o-rings. Of course be sure that the lid is tight and threaded on correctly, but be careful not to over-tighten the lid.

If your spa filter canister is cracked and leaking water, the best repair is to replace the canister / housing with new. For spa filters that are installed before the pump, small cracks might be successfully repaired with a strong epoxy repair product, but for pressure filters, I would recommend replacing the filter body, or the entire filter assembly.

Hot tub filters leak also at the drain plug or air bleeder knob, if loose or without thread sealant like Teflon tape. Some filter plugs also have a tiny rubber gasket or o-ring that will need replacement after many years.

For spa filter pipe leaks, determine if you have threaded fittings or the more common slip fittings, connecting at the bottom inlet/outlet ports. If a slip (glued) fitting is leaking, you'll need to replace the filter housing (or complete spa filter). For threaded fittings, screwed into the inlet/outlet port, you can cut the pipe and remove the fitting with large pliers. Replace with new, first smearing hi-temp sealant, followed by several wraps of Teflon tape (in a clockwise direction). Reconnect the pipes with a coupling or union.

If the union is leaking, unions on either side of the filter inlet/outlet - first try to tighten the union nut gently to seal up the leak. Use large channel type pliers if needed, if hand tightening alone doesn't seal up a leaking union. If pliers won't work, close the spa valves and open the union (water will spill), and replace the internal o-ring with lube.