How to Clean a Hot Tub Filter

Cartridges fail from oil, not from dirt. Body oils, lotions and sunscreen coat the pleats in a film that water cannot shift, and once that film is established the filter restricts flow even though it looks clean. That is why a rinse-only routine kills a cartridge in months while a rinse-plus-soak routine gets a year or more out of the same part.

Weekly: the rinse

1. Turn the pump off. On most tubs that means the power, not just the jets. Pulling a cartridge with the pump running can pull debris into the plumbing.
2. Remove the cartridge and look at it before you clean it. Gray and tacky is oil. Chalky white is scale. Packed with debris is neither. What you see decides what you do next.
3. Rinse from the top down, working around, with a fan-jet nozzle or a rinsing wand. Direct water into the fold, not across the surface. A thumb over a hose end cleans the outer third of a pleat and leaves the rest loaded.
4. Use a comb on compressed pleats if debris is packed in, gently and on a wet cartridge. Forced, a comb tears media.
5. Refit and restart. Two minutes, once a week.

Monthly: the soak

1. Rinse first, so the cleaner is working on oil rather than on leaves.
2. Mix the cleaner to the label in a bucket deep enough to submerge the cartridge completely. Half-submerged cartridges come out half clean, with a visible line.
3. Soak for the stated time, commonly overnight.
4. Rinse until the run-off is completely clear, then rinse for another minute. This is the step people cut short and it is the one that matters most.
5. Let it dry if you can, which is only practical if you own a second cartridge. Drying makes the next rinse more effective because dried-on residue lifts more readily.

The rinse-after-soak step deserves the emphasis. Cleaner left in the pleats goes directly into the water when the cartridge is refitted, and it is a leading cause of foaming that owners blame on swimwear detergent. If foam appears within a day of refitting a soaked cartridge, that is what happened — see why your hot tub foams.

At every water change: the deep clean

The tub is drained, you have the time, and there is no pressure to get the cartridge back in tonight. This is the moment for a long soak, an acid step if there is scale, and an honest assessment of whether the cartridge is worth keeping at all.

It is also the moment to flush the plumbing, because whatever is on the inside of the pipes is part of what keeps loading your filter. The sequence is on draining and refilling a hot tub.

The two-cartridge rotation

Everything above becomes easy the moment you own two cartridges. One is in the tub, the other is soaking or drying. You never have to choose between a proper overnight soak and a usable tub tomorrow, which is the single reason most cartridges only ever get rinsed.

Two aftermarket cartridges in rotation will outlast one premium cartridge used alone, which is covered on the cartridge roundup.

Mistakes that halve a cartridge's life

• Pressure washing. High pressure drives debris into the media and can tear it. Volume beats pressure here.
• Hot water. Warm is fine, hot softens the end caps.
• Bleach or the dishwasher. Both damage pleated media. The full reasoning is on vinegar vs bleach vs the dishwasher.
• Skipping the rinse after a soak. Foaming, every time.
• Refitting a cartridge with a deformed cap. Water bypasses the media entirely and nothing looks wrong.

Why the routine matters beyond clarity

Filtration is what lets your sanitizer do its job on the whole volume of water rather than on the part of it that is still circulating. Maintaining a residual is the core of the CDC’s hot tub guidance,^[source] and a restricted cartridge quietly works against it. Fifteen minutes a month is a very cheap way to keep that from happening.