How To Find the Best Hot Tub Filter Replacement

Updated: Mar. 17, 2023

Keep your hot tub water safe and clean. When it's time for hot tub filter replacement, here's what you need to know.

Your hot tub filter has a big job to do. It keeps the water safe, clean and clear by filtering out dirt, minerals in hard water, sunscreen residue, hair and other gunk.

A dirty filter can become clogged, resulting in dirty, unsanitary water. A clogged filter cartridge will also make the hot tub pump work harder and can potentially shorten its lifespan. That’s why most manufacturers recommend you remove and rinse your hot tub filter once a week — a garden hose is fine — and deep clean it with a cleaning solvent every three to six months.

With good cleaning and maintenance practices, your filter should last about two to five years, depending on how much you use the hot tub. If you don’t plan to use your hot tub in the winter, then here’s how to winterize a hot tub.

When it’s time for hot tub filter replacement, here’s what you need to know:

How To Find Your Hot Tub Filter Replacement

According to Pool & Hot Tub Depot, there are more than 300 sizes of hot tub filters, so there’s no universal solution for filter replacement. Here’s how to find the right replacement filter for your hot tub:

Where to look for the filter part number

  • On the old filter. With any luck, the part number is printed or stamped on the bottom of the existing filter, on the plastic ring that forms one end.
  • In the owner’s manual. You hung on to the hot tub owner’s manual, right? If the part number is not printed on the old filter, check the manual, which should provide a part number (or at least the measurements) you need for a replacement.
  • Measure the old filter. When all else fails, measure the length and width of the old filter, down to 1/16-inch. Include the thickness of the plastic end caps when you measure height, but don’t include handles, threading or any other parts that protrude from the end cap.

Shop for a Replacement Filter

There are two ways to purchase a replacement filter:

  • Order online. If you’re certain of the part number, finding a replacement filter is straightforward. You can search a major retailer like Amazon, or look to a specialty site like Leslie’s Pools, where you can enter the part number and call up the part you need. If you don’t know the part number but have the dimensions, Leslie’s, as well as Spa Daddy and other sites, have online search tools where you can input the measurements and call up cartridges that will fit.
  • Go to a pool and hot tub supply store. To remove all doubt, you can take your old filter to the store where you purchased the hot tub, or to another local supply store, and match it against a new filter cartridge. If they don’t have your size in stock, they may be able to order it for you.

Filter Replacement Tips

  • Study the photos. If you’re shopping online and going by measurements instead of a part number, study those photos carefully. Filter end caps of the same dimensions may have different-sized holes, coarse or fine threads or a protruding handle. Only the filter that looks exactly like your old one will work in your hot tub.
  • Consider square footage. Once you’ve found the right cartridge size, you may want to consider the square footage of your hot tub. A filter built to clean a 50-sq.-ft. spa, for example, has more pleats, which are closer together than one made for a 25-sq.-ft. spa. The larger capacity filter is harder to clean by hand, but does a better job at filtering water.
  • Buy an extra. Never let a worn-out filter keep you from enjoying your hot tub. Filter cartridges are often sold in multi-packs, so it makes sense to keep at least one extra filter on hand. Just don’t let your reserve supply run out before you buy new ones!