Spa Water Mold

Spa & Hot tub Water Mold

Spa Water Mold is a growing problem, especially in spas that are not maintained properly and/or are used infrequently.

The picture you see had been  properly maintained since its installation in August 2014. The picture was taken in mid April 2015...8 months! 

Once you can see the mold on the surface of the spa (as shown in the picture), you can be sure that the  plumbing lines, air lines & jets are completely infested. Many of you have been asking about this problem, so here is some information about Spa Water Mold, as well as how to treat it and how to prevent it.

For detailed information on biofilms, water mold & slime, is found below.

What it is & what it looks like: a naturally occurring fungus  (this is NOT a form of Algae; it is animal not vegetable).  Spa Water Mold (WWM) - along with Pink Slime - come from Biofilms. Spa Water  Mold looks like white mucous or tissue paper-like substance forms a heavy, protective coating providing the organism with an unusually high level of protection that is very resilient against halogen-based (chlorine, bromine) & non-halogen sanitizers or germicides.

Water mold can remain a contaminant even after treatment & it exists on the surface of PVC plastics, inside piping, filter cartridge housings, jet nozzles, etc.  If you see it on the inside surface of your spa, it is well established in all of the plumbing lines & air blower lines of your spa or hot tub. Water mold can re-contaminate long after it appears that it has been destroyed. 

Small quantities of Spa Water Mold can lead to a re-establishment of the problem caused by improper water & spa maintenance, environment, poor circulation & with "slow moving" water (behind jet nozzles, the back of the motor impeller, etc., areas that you would  think have a lot of water motion). 

Treatment: Purge, Drain & Refill using either Hot Tub Serum Total Cleanse or AquaFinesse SpaClean Puck. Badly infested spas may need to be treated a second time. Follow label instructions.

Prevention: Continue regular weekly maintenance that includes Hot Tub Serum Step 2 or AquaFinesse Hot Water Care Liquid.

Infestation of water mold after in a brand new spa just 8 months!
Infestation of water mold after in a brand new spa just 8 months!

spa & hot tub biofilms, mold & slime

Biofilms grow everywhere...

White Water Mold in spas & hot tubs is for all practical purposes, the covering for the real problem - biofilm.  If you think your hot tub water is clean and sanitary just because it looks clear, think again.

Yes, you may have shocked the water and even maintained a good chlorine, bromine, biguanide (Soft Soak or BaquaSpa) level, or installed a new Nature2 or Spa Frog cartridge but you've only controlled about 1% of the bacteria present! PoolSpaGuru helps you with how to get rid of mold in spa water

As we look for the root cause, we see more and more that there are real "problems" that are often undetected.

Biofilms in spas & hot tubs can and often do lead to cloudy water, foaming, odors, scale build-up on the heater (prevents efficient heating), and even corrosion (certain biofilms can have a pH of about 1.0 - very acidic) of any metal surface of the circulation system including heaters, filter parts, rails, etc.  Even degradation of pillows, covers & other spa accessories will occur over time.

By the way, if you have a jetted bathtub, this information is for you too!

First, what is a biofilm? A biofilm is a film or large quantity of bacteria that is living in and as a vast colony in the microscopic world. In the "big" world, you could call a coral reef a "biofilm." All biofilms are self-perpetuating and can be difficult to remove. Worst of all, biofilm love virtually any surface, especially wet or damp ones. But beware, even after drying out, the biofilm will not necessarily be dead but simply dormant. Did we mention that biofilms are relatively resistant to chlorine, bromine or other sanitizers?

Second, how do biofilms form? As just mentioned, biofilms form on any surface. In your spa or hot tub.  That means the seats, walls, bottom, skimmer baskets, filter cartridge and filter well, tank bodies, pump bodies and impellers, jets, handles, lights, air holes, heater plumbing, and especially the piping. There is a 5 steps process as to the formation of biofilms: Attachment, Colonization, Protection, Growth, and finally what I call Distribution.

Attachment is just that; the bacteria attaches to the surface. It wants a place to call home and grow. Bacteria want to be in relationships, so they find a nice surface to settle down and join up with a few of their closest friends.

After attaching to the spa or plumbing surface with their friends, Colonization takes place as bacteria multiply and divide, growing in number. According to studies, it is at this crucial point that this attachment is "irreversible." The bacteria colony is there to stay unless purposefully removed. This stage is typically accomplished in a matter of minutes or hours at most.

In the Protection stage, the bacteria colony or biofilm begins protecting itself against invasion. Invasion from environmental factors, "lethal" chemicals (such as chlorine or bromine), predators, anything that want to destroy it. In technical terms, the bacteria begins to excrete a protective coating called an "exopolysaccharide" film. The film is sticky or slimy and very hearty. Now the biofilm is ready to experience explosive growth.

Growth of biofilms is like a coral reef, the biofilm gets bigger and tougher. Super colonies of biofilm are actually absorbing certain chemicals that were meant to destroy them.

Now we come full circle to Distribution where these broken parts begin to attach to other surfaces or different parts of the same surface. And the cycle begins anew.

By the way, biofilms are everywhere. Pools, spas, bathrooms, kitchens, the funky look to your patio furniture, on your teeth (plaque is a biofilm), wherever there is a surface that can be damp you will find a biofilm.

What to do? Resistant to chlorine or bromine. Bonds with biguanides. Ionizers have no effect. You have to remove it. The picture to the left shows a brand new spa having the bio-film removed over several hours. But how?

Learn how to remove the biofilm below.


removing hot tub biofilms, spa water mold

How to deal with Water Mold & Biofilms in your spa or hot tub

Biofilms can be removed mechanically or chemically.  

Mechanical removal using scrub brushes, filter cleaners, etc., physically remove the biofilm from visible places.

Visible places would be the filter cartridge itself, filter tank, all spa surfaces where you sit or lie down, water line, pillows, skimmer baskets, etc. You can physically handle the object that needs to be cleaned.  This is one of the reasons why we as Spa & hot tub Professionals are so adamant about wiping the spa's surfaces on a regular basis - even every time that you use the spa.  Wiping breaks up and lifts the biofilm off from its cozy environs enabling the chlorine or sanitizer to kill it and the filter to remove it.  Be careful however to regularly clean & chemically clean the filter to remove the accumulations of "filtered" biofilms from the filter cartridge.

Keep in mind that biofilms are a direct contributor to chlorine demand, causing the spa to use significantly more chlorine, bromine or biguanides than if none were present.  Remove the biofilm, remove an important component to chlorine demand.

Chemical. In hard to reach places like hot tub plumbing lines & inside heaters, biofilms need to be removed Chemically. This is where so much biofilm (and about 99% of the bacteria) accumulates and thrives.  Biofilm is typically left alone.  It has all that it needs - a surface, moisture, and nutrients floating by. Keep in mind that biofilm doesn't need sunlight - it's not an algae so sunlight is not one of biofilm's needs. Biofilm does need "warm" water - 90° F or better for optimal growth, but as long as it's not cold, the biofilm will survive and grow just fine thank you.

Tried & true products such as natural enzymes (ActivNzyme, or SpaGuard Natural Enzyme) "eat up" much of the nutrients and other waste that contribute to biofilm growth thereby stunting it. But as biofilms become more resistant and more proliferate, a new arsenal of products must be considered & used.  Flushing products such as Spa System Flush, Swirl Away or Natural Chemistry Spa Purge have shown to be fairly effective in bio-film removal. The picture below shows a brand new spa having bio-film removed - results after 12 hours of a flush product.

Proven products such as AquaFinesse or Hot Tub Serum are added to the spa water and quite rapidly remove the biofilm from the hidden surfaces.  Both of these products have been successfully used in the American and European market and in industrial applications for several years. As with the physical removal products, loosened & removed biofilm particles must be filtered out of the water then removed from the system entirely. 

After the initial application, you will notice that the water become very cloudy and the filter becomes rapidly clogged as the filter traps all of that used biofilm.  Cartridge filters must be chemically cleaned to restore the filter to a proper working condition.  If biofilm removal has never been done before, it may be necessary or even advantageous to replace the filter cartridge - especially in older spas & hot tubs.  Chemically treating a brand new spa is often a great idea since most spas are water tested at the factory leaving wet or damp lines to accumulate biofilms for sometimes months at a time before it is delivered to your home. These products are completely compatible with all hot water care chemical systems (chlorine, bromine, biguanides, ionizers).

Because biofilms and water mold are naturally occurring, you must treat the spa or hot tub continually. Failure to treat will result in a fairly rapid re-infestation throughout the plumbing.

Click here for all of the AquaFinesses Spa products or here for the Hot Tub Serum products


biofilm, mold & slime prevention

Continued maintenance

Understanding that biofilms are naturally occurring, we have to deal with them. Period. And the best way to deal with biofilms is to prevent them from recurring. Customers who have thought that they had their biofilm problem taken care of are surprised that after stopping treatment, the biofilm, mold and slime return almost with a vengeance. 

For that reason, the prevention of biofilm, mold and slime MUST be continuous. Preventing biofilm, mold & slime build-up must be part of your regular spa and hot tub program. 

Whether we like it or not, all of us are stuck with these problems simply because biofilms, mold and slime are naturally occurring. I can't overstate that fact enough.

Why did it seem that this is a recent problem and not something that we've always dealt with?

One reason, I believe, is that absolute fact that the raw chemicals used to produce vinyl, PVC pip, and other plastics has significantly changed over the years. Many of the "ingredients" in the formulary were found to be carcinogenic (cancer causing), so in order to protect all of us, the federal EPA (Environmental Protection Agency) outlawed those certain chemicals. Unfortunately, although carcinogenic, those same chemicals provided longer lives to vinyl liners and many plastic products purchased today do not last nearly as long as though produced or manufactured back in the 1970's or 1980's or even earlier.

The good news is that we do have products that can prevent and treat these issues in an efficient manner.  AquaFinesse Liquid Hot Tub Water Care is NSF approved for use in potable (drinking) water. Hot Tub Serum has been approved by the EPA as a product that will actually kill the biofilm. In other words, we have very viable choices to care for our spas & hot tubs.

Which product do we like better? PoolSpaGuru.com likes BOTH products! Honestly... and we will recommend either one for your particular need. Both products have proven track records in dealing with biofilms, mold and slime. Both CAN extend the time in between Purge, Drains & Refills dramatically (in many cases once or twice per year as opposed to every 3 months).