What Is Biofilm?

Biofilm is any group of bacteria and other micro-organisms that stick themselves to a surface which is in regular contact with water. These micro-organisms will cover themselves in a protective layer of slime that is resistant to disinfectants (like chlorine or bromine). Biofilm can harbour harmful bacteria like Legionella (Legionnaire’s Disease), Pseudomonas Aeruginosas, Mycobacterium Fortuitum and E-Coli. It forms naturally under most conditions but thrives in dark, warm (>90°F), water rich environments. If the surface that biofilm is on dries out it will not die but rather it will go into a dormant state, reactivating once it comes in contact with water again.

How Does Biofilm Affect My Hot Tub?

As mentioned in the last section biofilm forms on any surface that is in water, or that is in consistent contact with water and thrives in warm, dark areas. The plumbing and filtration system in hot tubs provide an ideal environment for biofilms to grow. Add in all of the organics that humans introduce in the water like lotions, soaps, antiperspirants, and sweat and you’ve got a perfect environment for biofilms to grow. Because of this, even relatively new hot tub (less than a year old) can experience problems with biofilm.

Biofilm will greatly decrease your sanitizer’s (chlorine/bromine) effectiveness in keeping your water bacteria free as the residual in the water is constantly being used up trying to get rid of the biofilm. You may also notice it as a visible ring at the waterline or discolouration on your filter.

How Can I Get Rid of Biofilm?

Biofilm growing on the shell of the hot tub (usually at the waterline) can typically be wiped off with disinfecting wipes. Biofilm growth on filters and in the plumbing can be more difficult to remove however. As previously mentioned simply draining the hot tub and waiting for the plumbing or filter to dry out will not kill biofilm, just put in a dormant state. Once you refill the hot tub, or re-wet the filters, it will reactive itself and continue to grow.

In order to get rid of existing biofilm in your plumbing you will need to add a pipe cleaning product, typically right before draining. The cleaner is added with the jets running for a few cycles to allow it to properly circulate through the entire plumbing system. The hot tub is then drained and re-filled. To clean your filters properly soak them in a chemical cleaner made specifically for cleaning hot tub filters for a few hours or overnight.

How Can I Prevent Biofilm From Returning?

Once you’ve removed the biofilm from your hot tub you will want to keep it out. Enzyme based products like Natural Chemistry’s Spa Perfect or Eco One’s Spa Monthly can be added weekly or monthly to break down oils and other contaminants. These products rely on natural enzymes to break down the protective slime layer that covers the bacteria and will help to slow the formation of biofilm but won’t completely stop it. Plumbing cleaners should still be used at least once a year to clean out the hot tub’s plumbing and the filters should be chemically cleaned 3-4 times a year to rid them of biofilm.

While not cheap, we have found using AquaFinesse weekly to be the best way to keep biofilm out of hot tubs. It can even break down existing biofilm, allowing you to treat your plumbing without having to drain and refill the hot tub.

If you have any questions about biofilm or any other water care issue call our certified water care specialists at 905-666-5333. Like us on Facebook (www.facebook.com/TheSpaShoppe) or follow us on Twitter (@thespashoppe) to get notified when new blog entries are posted.

The Spa Shoppe

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Whitby, ON L1N 2K6



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