Biofilm builds up in the plumbing of hot tubs and covers itself in a protective layer of slime that is resistant to sanitizers like chlorine or bromine. It’s a relatively common problem in hot tubs and pools that causes increased chemical use and issues with water quality. Luckily it is possible to get rid of this funky slime and prevent it from becoming problematic. 

What is Hot Tub Biofilm? 

Biofilm is a greasy, slimy substance that builds up on pipes and filters in your hot tub. It’s a combination of microorganisms and bacteria made up of dead skin, sweat and oils from body lotions, deodorants and perfume. Bacteria comes from mold, algae, fungus and airborne contaminants or is introduced to the tub by bathers. Biofilm creates a slimy outer layer to protect itself from the water’s sanitizers and chemicals but it becomes resistant as it continues to grow. Even a relatively new tub can experience problems with biofilm.

Biofilm is essentially a sponge for hot tub sanitizers like bromine and chlorine. Most of the sanitizer gets used up, killing the sanitizer-resistant slime layer surrounding the biofilm leaving the biofilm itself relatively undamaged. Once the sanitizer has been spent, the biofilm can regrow its protective layer. Other bacteria still present can also then begin to multiply. This buildup of bacteria can cause a range of water quality and safety issues, most commonly foamy, cloudy water and a visible oily ring at the waterline of the hot tub.

Even if you shower beforehand, dead skin, hair and sweat will still find their way into the water. Biofilm is rarely seen, so in most cases you just see the effects of it. When biofilm is present, it’s more challenging to maintain sanitizer levels. When chlorine and bromine are mixed with water they turn to acid, lowering your alkalinity. When alkalinity gets below 80ppm, the water becomes very acidic and can cause itchy skin, rashes and can even start to degrade the o-rings, seals and gaskets in your spa which will lead to leaks and expensive repairs. 

How Can I Get Rid of and Prevent Biofilm?

Removing biofilm requires some effort depending on the severity of contamination. Start by removing your filter and sanitizing it to ensure a dirty filter can’t recontaminate your tub. Next use a biofilm cleaner to decontaminate the plumbing. You’ll also need to super chlorinate the tub to kill any surviving pathogens. After the chlorination period, drain your tub and run water through to ensure the biofilm remover will reach the plumbing system. If biofilm or other buildup is visible after emptying your tub scrub it off, then install the clean filter and refill your tub.

To prevent the build up of biofilm there are a number of things you can do. Keep your tub covered when it’s not in use and clean the filter regularly. You’ll also want to keep a close eye on your water chemistry. Test the pH and alkalinity of your tub water weekly aiming to keep the pH level between 7.2-7.6. When the chemicals are balanced properly, they can do their job to eliminate bacteria in the water.

Consider allowing the water to circulate even when the hot tub isn’t in use. Proper circulation of the water ensures water cannot stagnate anywhere in the spa. You’ll also want to drain your tub every few months and thoroughly clean it. With a little diligence and care, your hot tub will remain the relaxing spa you intended it to be. Give us a call with questions at 970-879-4390 or contact us here.