Hot Tub Decontamination & Getting Rid of What Ails Your Spa

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With the COVID-19 pandemic dominating headlines worldwide, following the recommendations of health authorities is critically important. While you are not likely to get the Coronavirus from a hot tub (unless you are tubbing with infected people), it seems rather timely to discuss hot tub decontamination.

Turns out, lots of nasty microbes just love hot water, and they can cause big problems for hot tub users. Cryptosporidium (AKA Crypto), Legionella, and Pseudomonas are but just a few little gems you don’t want hiding in your tub.

What to do when you suspect your hot tub is harboring some of these un-pleasantries?  Have yourself a good old fashioned hot tub decontamination session, that’s what! Here’s what you want to do:

Phase 1 - Decontamination

Spa Cover

Thoroughly clean spa cover surfaces, paying special attention to the underside. Removing the foam cores (if possible) will allow you to inspect and clean them separate from the outer jacket.

We recommend using Clean All Spray, a gentle cleaner that will not affect pH, to remove dirt and other particles. Once everything is clean, seal it with 303 Protectant.

NOTE: If hot tub cover is in bad condition or waterlogged, replace it. Waterlogged covers harbor mold, mildew, and bacteria, and may continuously inoculate the spa water with microbes. If you need a new hot tub cover, consult the Spa Cover Replacement Guide.

Spa Filters

Remove and inspect your filter cartridge(s). Throw them away if they’re in bad condition or older than a year or more. Check out our handy Filter Finder if you need replacement filters.

If serviceable, Clean the Filters using Power Soak Filter Cleaner per label instructions.

After cleaning and rinsing filter, completely submerge it in a strong solution of Dichlor Chlorine and water. In a clean bucket, dissolve about 1 teaspoon Dichlor in 3-5 gallons of water, soaking the filter for 2-4 hours. Also, inspect and clean the interior of the filter housing and skimmer.

Hot Tub Vessel Super-Chlorination

Now that we’ve addressed the cover and filters, let’s focus on the spa itself. We’ll be super-chlorinating the spa water to at least 100 ppm with Dichlor Granular Chlorine.

Pre-dissolving the chlorine in a bucket will prevent damage to your spa’s acrylic surface from direct contact of chlorine granules. 100 ppm is too high to measure with test strips, so dose your spa using the following measures:

  • 100gal = 2.5 oz. (4-3/4 TBSP)
  • 250gal = 6.25oz. (3/4 cup)
  • 500gal = 12.5oz. (1-1/2 cups)
  • 1000gal = 25oz. (3 cups)

Raise the water level in the spa to about 1/2 to 1 inch above the normal high water mark. Circulate the spa water on high speed for 30 minutes with spa cover closed.

With jets on maximum, open air control valves for 5 minute intervals during this process to help disinfect air lines. If your spa has an electric air blower, run it for a minute every five minutes.

NOTE: Avoid inhaling vapors or mist from spa during decontamination.

Flushing the Plumbing System

Next, and before draining, add Spa System Flush per label instructions. Circulate water for an additional 30 minutes, continuing to turn air injectors and/or blower on and off at above intervals.

Spa System Flush is critically important. It breaks up and flushes away inaccessible oily deposits, dirt, and other debris from your spa’s internal plumbing system. It completes the cleaning process from the inside out.

Phase 2 - Water Replacement

Reinstall the cleaned and sanitized filter, or better yet, a new Filter Cartridge.

Refill the spa with fresh water. Now balance the water, paying close attention to Total Alkalinity and pH.

Using a PreFresh Spa Fill Filter reduces many impurities, including odor-causing organics. Starting with pure water reduces demand on your spa chemicals. Highly recommended for well water users or when source water is questionable.

Do not add sanitizer yet, but continue to Phase 3.

Phase 3 - Verification

The final and most important step is verification of decontamination. Understand that contaminants place a demand on, or deplete free chlorine residual. Now shock the refilled spa with 10 ppm of Dichlor Granular Chlorine, pre-dissolved in a plastic bucket of water.

This is around 1-1/4 oz. (2 tablespoons) per 400-500 gallons. Check the spa water with Test Strips to confirm about 10 ppm.

Let the spa to circulate for 8-12 hours with spa cover on so sunshine doesn’t degrade the chlorine level.

After this circulation period, check for free chlorine with Test Strips. If you get a residual free chlorine reading on your test strips, decontamination was most likely successful.

Still no free chlorine residual present? That means there is still excessive demand, indicating the presence of contamination. If there’s no free chlorine is present, repeat the decontamination procedure.

After you’ve verified no contamination exists, there’s one more very important thing to do: ENJOY YOUR HOT TUB!

Questions about the process? Can’t get it quite right? SpaDepot is here to help. Give us a call or shoot us an eMail!

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