"Spa snot"?

[Hilton]

I'm getting a build-up of a white substance in my skimmer, in particular building up on the thermometer and any items that may be in the basket (ie leaves). It is very thick, has the exact look and consistency of mucous, and is not the usual crud that builds up in hot tub skimmers.

This is actually my second occurance; the first was two weeks ago in a 10,000L indoor hot tub (concrete/tile, sand filter). The second is now in a 5,000L outdoor hot tub (concrete/tile, sand filter). Both are maintained in the neighbourhood of 7.5/130, 3-5ppm FC, but the FC occasionally drops to near 0 or goes up to 10 if usage is misjudged.

This is what happened at the first tub:
For a week and a half, I was cleaning it all off and did a mild shock (10ppm) a couple of times. It continued to grow back, so I triple-shocked the hot tub (600g Cal Hypo in 10,000L) for five hours. Afterwards, I drained, scrubbed the surfaces and skimmers, used a pipe cleaning product (Swirl Away), and used a filter cleaning agent (BioGuard Filter Brite). However, I think it may still be coming back; will know for sure in another week.

I am hoping someone here has some idea on what this is. The local health authority has apparently never heard of/seen anything like it. Nor has any of the three pool stores I have visited (including my main supplier); a rep from BioGuard suggested it was a bacterial colony, hence the attempted treatment mentioned above. I am also worried that I transferred this into the second tub on my own hands, despite some serious hand washing and scrubbing.

 

[waste]

Sorry you've got 2 tubs with this

I'm pretty sure it's a 'bio-nasty' and chlorine ought kill it. (Of course, maybe it's just facial tissues [i.e. Kleenex]- it is cold and flu season )

Are the tubs in regular use, all functions? I've noticed bio-slime come out of unused lines (like a flooded blower line) - the fix is easy, simply run that line a couple minutes each day to allow the exchange of sanitized water

HTH

 

[Hilton]

They are used several times per day, nothing unused.

The slime in the first one seems to be returning - there was a layer of it on the thermometer today. Not much, but that was how it started last time.

I've got the second one sitting w/ 400g CalHypo added 4 hours now. Going to leave it closed overnight. Not sure if I am going to drain it or just neutralize it...

On my phone right now, will post more tonight.

 

[chem geek]

Next time you do a drain/refill of the hot tub, try using Spa System Flush. Several people have reported better results at removing biofilm and organic deposits using this product compared to Swirl Away. Once you get rid of the film, you should be able to keep it away IF you can maintain the chlorine level consistently and not let it get to zero.

What are you using to chlorinate these hot tubs; what type of chlorine and what method (manual, automated)? These sound like larger commercial units. If they are residential, then you might consider doing initial chlorination using Dichlor and then switching over to bleach or chlorinating liquid after the CYA level has risen to 20-40 ppm (target 30 ppm). This will let you keep the FC level up at around 4 ppm or so without this being too harsh on hot tub users. Note that without an ozonator, the rough rule-of-thumb is that it takes around 3-1/2 teaspoons of Dichlor, 5 fluid ounces of 6% bleach, or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize every person-hour of bather waste (so scale accordingly).

 

[Pacifica]

Is the spa indoors? If this is the case, then the spas should be drained much more often. I would try doing that as well. A spa that is used several times per day would be considered high usage and should have the water replaced frequently. The reason being, is that it is much harder to oxidize the water because the hypochlorous acid that is oxidized needs to gas off from the spa for it to work correctly. Meaning that the hypochlorous acid is raining back down into the spa thereby making it hard to oxidize your water.

 

[Hilton]

As mentioned in the first post, the first spa was indoors, the sceond one is outdoors (under a roof). However, all our indoor pools and spa areas have large air exchange/dehumidifier systems that run 24/7; gassing off is not a problem. I have never once been able to get a CC reading over 0.5, and even that is rare.

All spas are hit every Monday with potassium monopersulphate, and are drained each time the TDS reaches 1500 or CYA builds up to 150. This typically occurs every 4 weeks.

 

[chem geek]

With the CYA building up it sounds like you are using Dichlor or Trichlor for chlorination (which is it?). 150 ppm CYA from Dichlor would be 165 ppm FC or over 4 weeks that is 5.9 ppm FC per day. If you were using Trichlor, then that would be 246 ppm FC or 8.8 ppm FC per day.

When the CYA gets high (technically, when the FC/CYA ratio gets low) the active chlorine level drops so rates of oxidation and sanitation drop potentially allowing bacteria biofilms to form (especially if the chlorine sometimes get to zero). It would be better if you switched from stabilized chlorine (Dichlor or Trichlor) to unstabilized chlorine (chlorinating liquid or bleach) after the CYA has built up to around 30 ppm or so, certainly no more than 50 ppm. Remember the following chemical facts that are independent of concentration of product or of spa size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

I'd still do a decontamination on your next drain/refill, but you should have fewer problems if you control the CYA level. Note that it is VERY important to get the Total Alkalinity (TA) level very low, perhaps to 50 ppm, when you switch to a hypochlorite source of chlorine. You could also consider using 50 ppm Borates (Proteam Gentle Spa or boric acid) which will help for pH stability.

 

[Hilton]

I should add this detail: I've noticed a constant drop in TA every day with this "biofilm" I have. Every day I find it at 70-80, down from the 130 I had raised it to. This does not happen normally. And I do usually have a 30ppm borate level (added via BioGuard Optimizer Plus).

Solid trichlor are used in all the spas.

I've thought about switching to bleach or an unstabilized product, but I was informed by our pool store (whose products I am required to use and advice I am supposed to follow due to the company policy of leaving the blame on them) that they don't recommend using bleach for assorted reasons, and that the Cya buildup was not an issue until it hit a very high level. I believe my only other alternative in their product lines (they carry BioGuard, SpaGuard, Natural Chemistry) is SpaGuard Chlorinating Crystals or something, which is Lithium Hypochlorite. I think that the cost of this, due to the size of my spas, is quite a lot higher though. (Same reason I use very small doses of Pool Refresh at 25 cents per week, which is a concentrated version of Spa Refresh which would cost $20 per week.) There is also the Calcium Hypochlorite, of course, but that just doesn't work over any length of time due to the CH raise. In addition, because I am only at each of these spas once per day (and not at all on weekends), I REALLY need something that is added by erosion.

Does ANYBODY carry a puck or stick based product that is an unstabilized chlorine?

 

[chem geek]

Unfortunately, the chemistry of chlorine does not allow for a slow-erosion puck of unstabilized chlorine except for a Cal-Hypo puck that tends to fall apart too quickly. Even Trichlor pucks aren't well suited to spas because they tend to erode too quickly at hot temperatures so you must have the feeder dialed down somewhat. Note that Trichlor is acidic and will drop TA over time. For every 10 ppm FC added by Trichlor, the TA will drop by 7.1 ppm. So the large drop you are seeing is truly strange.

There are automatic feed systems that could be used such as peristaltic pumps and there are saltwater chlorine generator systems for spas. Those would be the automated options. However, without some sort of feedback measurement such as ORP, you won't be able to control the chlorine level as the bather load goes up and down.

The other alternative to get more automatic dosing is to use bromine instead using a bromine floater since bromine tabs dissolve slowly. That still won't solve handling the variation with bather load, however.

 

[PoolGuyNJ]

I would say the drop in alk indicated the spa snot is a biofilm and it is likely producing an acidic discharge as it's waste.

You're going to have to limit the body count per hour. No if, ands or buts about it. People won't like the idea of waiting but they'll like getting rashes or worse even less. This is a capacity issue and a serious change in the operating procedures is called for.

The switch to bromine is a good idea. Then periodically close the spa to patrons and add some liquid chlorine or bleach to free up the spent bromine.

Scott

 

[Hilton]

Haven't made it back here for a while. Bromine is not an option, this is a commercial hot tub and the health authority requires chlorine, period.

The snot problem disappeared for a long while - it cleared up after the second time I shocked the tub to >50ppm for 24 hours in both tubs.
I did have something similar reappear in small amounts over this past weekend at one tub, but it may have been something different - the entire tub was absolutely gross with a scum line that was nearly an inch high and 1/8" thick. I cleaned it up, and it doesn't seem to be coming back.