Hot Tub Filter FAQ

As a hot tub owner, it’s important to be as familiar with your spa equipment as you can. Being knowledgeable will mean that you will know how to fix any problems that arise and will know how to keep your system functioning without any hitches. If you’re THAT kind of hot tub owner, you’ll love having the answers to the most frequently asked questions about the hot tub filter.

What is a hot tub filter cartridge?

Hot tub filters have been made in cartridge form since the 1960s. Manufactured as a cylinder with fabric pleats, it creates a large surface area that allows water to flow while placing less strain on the pump because more dirt and debris are caught in the folds. The filters are made either of polyester or another similarly fine material that is an efficient filtering surface.

What are filters made of?

Filters are made up of 3 elements: the end caps (made of plastic), a core structure that lends size and shape to the filter (made of PVC), and the pleated media (typically a polyester with a continuously graded pore structure).

The pleats are what make the hot tub cartridge filters special. It allows a large amount of material to be used in just a small container. The fabric in your filter holds onto the impurities until the filter can be cleaned or replaced.

Why is it important that hot tub filters are in good condition?

Your hot tub’s filtration system is really the unsung hero of the whole unit. If your filter is worn out or clogged, it will affect the rest of your equipment. Clogged filters are the leading cause of repair service calls and spa pump failure. There may not be anything wrong with your pump or heater, but the high limit switch has shut off the equipment to protect it from overheating because of the restricted water flow.

How often should I clean my spa filter?

Ideally, you should be rinsing off your spa cartridge filter every 2-4 weeks, depending on your spa usage (frequency of use + number of bathers).

How do I clean my filter?

For your typical cleaning, remove the filter from the spa and use a garden hose to wash it at a 45° angle both on the interior and the exterior until all the dirt and debris is cleaned out. Spray between each pleat to make sure that everything is out.

Is there any way to make cleaning it easier?

You can use tools like a filter flosser or an aqua comb to help with these cleanings. Both attach to the end of your garden hose and work to deep clean with less work while getting deep into the filter folds. The filter flosser cuts the cleaning in half and will help you use 50% less water and eliminate splash back problems—a nice step when trying to conserve resources.

What do filter cleaning products do?

Hosing off the filter isn’t always adequate for proper filter maintenance, however. Algae, scum, lotions, and body oils can cling to the fibers of your filter and won’t budge with simple water pressure. For cases like these, you’ll need to soak your filters in a filter cleaner like the ones offered by Spa Pure, Leisure Time, or ProTeam. You should use a filter cleaning product every 3-4 months or every time you empty your spa. You should make it a more frequent practice if you’re a heavy hot tub user.

Fill a bucket with water and add your cleaner according to the instructions on the bottle. Cleaners will have you soak the cartridge anywhere from 30 minutes to overnight, depending on which kind you use. Soaking in the cleaner solution will strip off the contaminants that may be deeply set in the folds. These cleaners are compatible with most all sanitation systems and won’t affect your water chemistry.

How do I breakup scale deposits in my filter?

If your fill water tends to be calcium and deposit heavy and that tends to accumulate in your filter, you can add it to a muriatic acid bath after cleaning thoroughly to dislodge the calcium. Just add some muriatic acid to water at a ratio of 1:20 and let soak until the bubbling stops. Rinse off and let dry.

Give your filter time to dry completely, keeping it somewhere it is safe from dirt and debris. Letting it air out before installation will destroy any microorganisms lurking inside your cartridge’s folds.


A lot of hot tub owners will get an extra filter so that they have a clean and dry filter ready to swap out with the one that needs cleaning. This means no wait time and a filter will always be installed. You should let your filter dry completely after cleaning, and having an extra one on hand will make it so you can bathe again right away.

How often should I replace my filter cartridge?

It’s recommended that you replace your filter cartridge annually, or every two years if you have two different cartridges you swap out for every cleaning. This will give you an extra year for each cartridge if you’re a casual user and are gentle on your equipment.

How do I know when it’s time for a new filter?

If you have any doubts, there are a few ways to know if it’s time to be replaced. Like we said, an old, dirty filter does not help you or your hot tub and may end up costing you more in the long run if you have equipment damage as a result.
  • If your filter is discolored (brown, gray, green, or dark yellow) even after a thorough cleaning, it could mean the fabric has deteriorated and isn’t functioning properly.
  • If you have moved into a new home with a spa or have transferred ownership of a hot tub, changing the filter is a good way to start fresh.
  • If the pleats in the filter cartridge have started to go flat or the media has lost its fibrous sheen.
  • The plastic caps on the top of bottom have cracked or have begun to separate from the fabric.
  • The material begins to shred or come apart.

You can use the hot tub filter search tool at hot tub warehouse to help you figure out which cartridges work best in your hot tub.

How can I extend the life of my filters?

Well, since you asked…here are some additional tips to help improve the longevity of your hot tub filters:

  • NEVER use a power washer or dish water to clean out your filter cartridge - that kind of high pressure is very damaging.
  • NEVER use household cleaners or laundry detergent as opposed to a filter cleaner. These leave behind residue that will cause major foaming problems in your hot tub water.
  • NEVER use bleach to clean the material in your filter cartridges. This may get them looking clean, but bleach will break down the fabric will not filter properly.
  • ALWAYS keep a spare filter on hand so you always have a clean and dry filter available during cleanings.
  • ALWAYS follow your equipment’s instructions for removing and reinstalling your hot tub filter cartridges.
  • ALWAYS maintain proper water chemistry and a follow a hot tub maintenance schedule. Doing so will be easier on your filters and hot tub equipment. If your filter stays clean, you won’t have to overcompensate with more chemicals.
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