Spa Filtration & Sanitation Tips for your backyard hot tub

Spa Filtration & Sanitation Tips for your backyard hot tub

by Rob Cox via Poolcenter

Hot Tub Tips: Filtration and Sanitation

If your backyard paradise includes a separate spa or hot tub, you know how important it is to maintain your spa water chemistry and proper filtration.

A spa is not just a little pool, it requires special attention to keep the water clear and clean.

This blog post takes a look at the unique differences in spa care, as contrasted with swimming pool care.


Much like a pool, hot tubs use a circulation pump to force the water through a filter to remove micro-contaminants and bather waste. Most spas use a cartridge filter, which is removed and hosed clean every 2-6 weeks, depending on size and condition of the spa filter.

Running the Spa Pump: In a swimming pool, the water should be turned over 1-2 times daily. This means that all of the pool water should be run through the filter, once or twice daily. For most spa owners, it would be recommended to double the turnover rate, filtering all of the water 3-4 times per day.

You may have a spa pump that operates on low-speed all the time, and on high when you are using the spa. If you have a time clock, you can experiment with running the filter on low speed for 8-12 hours daily, or two runs of 4-6 hours each.

If experimenting with reduced filter run times, keep a close eye on the water chemistry and water clarity. If either suffers, add a few more hours to the time clock.

Maintaining the Filter Cartridge: On some spas and hot tubs, the filter cartridge is woefully undersized. If you’re cleaning the cartridge too often, here’s some tips for improved spa filtration.

Spa cartridges are often available in higher square footage. For instance, you may find thecorrect cartridge for your spa available in both a 35 sf and 50 sf model. The 50 sq. ft. model has 30% more filter surface area.

Cleaning your spa cartridge with Spa Filter Cleaner is recommended every 3-6 months to remove clogging minerals and oily deposits, which inhibit filtration, and cause short filter cycles.

Allow your spa cartridge to dry completely before re-installing it. Full air exposure and drying kills remaining bacteria and contaminants that are hiding in the pleats.

When re-installing the spa cartridge, be sure to seat it fully into the base of the spa filter, so that water is not able to bypass the spa filter cartridge.

Replace your cartridge(s) every 1-2 years; or if cracks or rips develop, or if you find yourself cleaning the spa cartridge twice as frequently as when new.


This is where an easier distinction is drawn between pool and spa care. The water chemistry in a spa changes dramatically when several adults jump in – the pH will will spike, and the sanitizer level will drop – quickly. You can understand why – with the volume of water being so small, that the water chemistry changes so much.

We also have the element of high temperature in a hot tub. Hot water more rapidly depletes sanitizer level, and the fast evaporation of spa water can increase your hardness levels and total dissolved solids.

Maintaining Spa Sanitation: Bromine is the sanitizer of choice in a Hot Tub, it’s more stable than chlorine in a hot water environment, and retains more efficacy in the face of swings in pH level. Pool chlorine tablets should not be used in a spa. Ozone and Mineral Purifiers are often used in spas to supplement the level of Bromine.

Ozonators or Mineral cartridges such as Nature2 or Spa Frog, keep your sanitizer from working too hard.

Shock your Spa with a good quality Spa Shock, after heavy use, or at least twice per month.

Test your spa water several times per week, to ensure proper levels of sanitizer, pH, Alkalinity and Hardness.

Use Spa Purge every 6-12 months, when you drain the spa, to clean Bio-Film Bacteria from hidden areas.

Open your Spa Cover weekly during periods of non-use, to allow the spa water and the spa cover to “breathe” for an hour.