NOTE: If hot tub cover is waterlogged or smelly it should be replaced. A waterlogged cover will likely be infested with mold, mildew and bacteria and continuously inoculate the spa water with more micro-organisms.


Moldy EPS Foam CoversBiofilm is a complex association of micro-organisms which adhere to hot tub surfaces, particularly inside the plumbing, where they are difficult to remove. Biofilm may contain bacteria, viruses, mold and parasites as well as dirt and polysaccharides to improve adhesion to surfaces. It grows within the plumbing systems and jets, forming a slippery film. Micro-organisms inside the biofilm layer are somewhat protected from sanitizing agents. They present a danger to the bather if exposed before sanitizers can kill them. It is important to remove biofilm and prevent it from reforming as it can, under certain circumstances, cause disease.

There are several types of micro-organisms, which can grow in spa water: bacteria, fungi, protozoan, and viruses; some of these are pathogens. These organisms can come from a variety of sources including other humans and animals, from the ground, water or even airborne sources. A poorly maintained spa can form biofilm in the plumbing system and on surfaces to allow organisms to multiply.

Culprits include various forms of Pseudomonas, which can affect ears, eyes, skin (rashes) and the respiratory tract. Another is Mycobacterium avium, which can cause flu-like symptoms.

Interestingly, researchers have found that many people who complain of “allergic reactions” to sanitizing chemicals are actually suffering from skin rashes caused by bacteria due to inadequate sanitizer levels!

Hot tub folliculitis is a condition caused by Pseudomonas bacteria, and is often seen where spa sanitation is absent. The most common symptom is an itchy rash or small reddish bumps, sometimes confused with bug bites. It can develop into more serious problems. This condition usually clears without scarring. It may recur if the infected hot tub is not properly cleaned and disinfected.