White Water Mold In Hot Tub

by Charlie
(Hot Springs AR)

I have cleaned my hot tube with "Clorox", aqua fresh, brought the bromine/chlorine level to 4-5 and cleaned with ahh-some twice. Drained tub after each of these scrubs, totally cleaned surface of tub, refilled with pure clean water.

It looks just great until I turn the pumps on, and then all the white mold comes out again in big tissue paper lumps and small parts. I clean this out with a screen until clear and turn pumps on again, and out comes the mold. What am I doing wrong????

Hi Charlie. You're not doing anything wrong. It's just water mold is everywhere and needs to be rinsed out. It know it's a pain. I've done it several times for customers. One thing I would recommend is to reduce the pH to 7.0 - 7.2 and increase and maintain the chlorine level up to 15 ppm. This is the only way to kill the mold.

Then there's the process of cleaning the filter. You should be using a clean one to capture the particles and rinse very well. When the process is complete, get a new filter. Or if your hot tub filter is sand, backwash each time you run a complete cycle. And be sure there's enough sand in the filter. Top it off if needed.


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Is This White Water Mold?

by John

Last summer we started seeing white flakes in the filter basket. We took the basket to our spa dealer to find out what it was. For every tech there, we got a different explanation: bacteria, soap scum, hard water, mold caused by water, mold in water, etc.

They tested our spa water every other week and it was always the same thing--too high pH and too low chlorine levels. No one ever mentioned water and mold. They told us to add more chemicals like bromine. Our spa is 2009 and came with an ozonator.

We added bromine, increased the shock frequency, etc, but the white flakes continued to fill up the filter basket every other day for mold removal. The spa water was always clear.

Then in November we noticed a lot of yellowish foam when we ran the spa that left a ring around the spa. Our dealer kept saying they didn't really know what caused the flakes or the foam. They sent out a tech to check it out and he discovered the ozonator was no long working for mold removal. It probably stopped abut the time the flakes appeared.

They recommended we remove the ozonator and just use the chemicals. We removed the ozonator but had to find an alternative to the increase in chemicals because they exacerbated my health issues and we had to find something else. We decided to try a natural enzyme system.

We followed their conversion instructions, but still had the white flakes in the basket. They said it was probably the mold in water. We've done the decon. process 3 times, put in new filters, prefilter to fill the spa, etc., but we still have white flakes in the basket. Now we don't know what to do. Please advise.

We haven't added the enzyme system yet because we need to identify and rid the spa of these flakes. No one has used the spa in over 4 months. Do we really have a water and mold problem? If yes, how to we proceed? This is what's in the filter basket. It varies from hour to hour how many white flakes are in the basket. We still see white bits on the bottom of the spa.

We've never had anything floating on the top of the water, they've always been on the bottom.

Thanks for the question John

By what you describe it sure sounds like white water mold in your hot tub.

It would be great to have your complete chemical readings:

Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper) and names of any algaecides you may have used along with clarifiers, phosphate removers, and/or flocs. It makes troubleshooting much easier.

Hot tubs are more harsh on chemicals than the swimming pool simply because of the temperatures. Your hot tub probably runs between 100 - 104 degrees while the swimming pool runs much lower.

Your chlorine could be bottoming out because you don't have any/low stabilizer (cyanuric acid/CYA) in it, or you could have too much. Without the readings it's difficult to say.

CYA range is 30 - 50ppm. You need to run the chlorine a bit higher, perhaps 4 - 5ppm because the heat will eat up the chlorine very quickly. That's why many hot tub owners opt for bromine. It's a bit more stable than chlorine and can better resist the heat.

What I've found to be the best way to get rid of water mold is to take everything out of the spa and bring all of the levels up to the proper reading. TA 80 - 100ppm, pH between 7.4 - 7.6, and CYA 30 - 50ppm, then do a double shock. Don't worry about the calcium hardness right now. Clean all of your hottub covers and NO heat in the hot tub while doing this process.

Allow to filter for 3 - 4 days, keeping the chlorine level above 10ppm as best you can, then drain and clean the inside of the hot tub, the filter, and baskets. Water mold is all throughout the hot tub, not just on the surface, so a shock is needed.

Next, refill, balance the chemicals, and shock again. Repeat the process above. Drain, clean, refill, and balance the chemicals again.

Remove the filter(s) and clean with a good filter cleaner. GLB Filter Fresh is a good option. Soak the filters for at least 24hrs and rinse thoroughly.

Unfortunately there's no easy quick fix to get rid of water mold. It's going to take time and patience.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Hot Tub/Spa Questions" category.

Check back to this post for updates or answers.

If you need immediate assistance (within 24 hrs) or for emergency personal assistance, you can make a donation of your choice and I'll answer your questions by phone.


Hope this helps and have a great Summer.


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