Biofilm in Spas

The word “biofilm” is gross and scary – to hot tub owners, it should be. A biofilm is a biological microorganism in which the cells stick to surfaces. This hot tub problem is becoming more and more common and is referred to as “slime” because of the extracellular polymeric substance they contain – big words meaning tough to get rid of!

Formation of Biofilms

Biofilms start to form with the attachment of free-floating microorganism to a surface. The initial build-up of biofilms is very weak and can be removed easily. If they are left to build up more colonies, they can be very hard to remove from surfaces. Biofilms have an anchoring system called pili which is a cell adhesion structure. Biofilms are usually found on solid substrates submerged in or exposed to an aqueous solution. A prime example of an aqueous solution is a hot tub. A hot tub is a very humid climate which is an excellent place for biofilms to grow. Given sufficient resources for growth, a biofilm will quickly grow to be macroscopic which is visible to the naked eye.


formation of biofilm

Why should I care about biofilms as a hot tub problem?

It is important to remove biofilms from hot tubs because of the effects it can have on water chemistry. This is the main source of sanitizer demand and it particularly unhealthy for someone to sit in. Chlorine/Bromine demand is the main source as to why hot tub owners go through more chlorine or bromine. They are unhealthy because essentially they are bacteria! Bacteria are never healthy to sit in and should be removed in order to maintain clean water.

I have a biofilm – what now?!?

There are two different ways biofilms can be removed. They can be removed mechanically which is taking a brush, towel or filter cleaners. This method only works for biofilms that are in visible places on the hot tub. When removing biofilms from the acrylic surface of a hot tub, make sure the towel or brush is soft. This is so that the towel or brush does not scratch the acrylic surface. Filter cleaners are great at removing biofilms from filters. The second method to remove biofilms is doing a chemical cleaning of the plumbing lines and inside heaters. This where towels and brushes cannot get inside. Hot tub owners should purchase a plumbing and heater cleaner in order to remove biofilms. Also regular oxidation of hot tub water will help prevent the build-up of biofilms. Oxidation is the removal of bacterial wastes and unwanted contaminates in hot tub water. This makes chlorine or bromine more effective and can help focus on keeping biofilms from building up.

If you have ever had or ever develop a biofilm, TELL YOUR SPA CARE PROFESSIONAL RIGHT AWAY and they will work with you to put together a programmed approach to spa care to remove and prevent the problem for good!


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