CYA over 100 with yellow/mustard algae

[PoolDoc]

Perfect! (You're the droid I'm looking for . . .)

Mustard algae susceptible pools are one of the puzzles we have NOT solved here on the forum. It is definitely an issue that exists, but I've never figured out why. Having run as many as 25 large pools (>100,000 gallons) in a summer season, I saw problems with certain pools, year after year, but never saw those problems on other pools, even though the pools were operated with the same chemistry and with similar loads.

I tried every treatment I could -- quats, polyquats, copper, even Simazine when that was still legal. None of those worked. It's continued to be an issue from me, since the one remaining local pool I service (~200,000 gallons) has always been susceptible to mustard algae.

The only two treatments I had not tried were borates (> 50 ppm) and phosphate removers (PO4 < 200 ppb). I decided to try one or the other on my local pool this winter, and went with phosphate removers simply because it worked out to be cheaper. It turns out the fill water in that part of town may be the problem: phosphate levels, exiting the tap, are around 3 ppm or 3,000 ppb. I haven't checked with the water company, but that may be typical for water companies with lots of old iron pipe in their service area, since certain phosphates help reduce iron corrosion.

I started dosing in September, and got PO4 < 250 ppm by November. (I was concerned about filter problems, but didn't encounter any.) The results have been spectacular! My chlorine consumption is 20% of what it has been in previous winters, and yet there is no algae whatsoever.

Your results offer a data point suggesting that borates may NOT be a solution to this problem. If you're willing to try, your pool would make a great second test point, especially since you have had recurrent mustard algae. It you're willing to give it a go, you need to do the following:

1. Order the Taylor phosphate kit. I've tried 4 or 5 kits. Most are awful. The AquaChek is not as bad, but is really only readable at low levels -- you can use it once your phosphate is very low, but it's not going to help you find out how high it is now.

Taylor Technologies K-1106 Phosphate test kit
Hach Company 562227 Phosphate Test Kit (Aqua-Check)

2. Order 2 quarts of Clorox (was: Kem-Tek) phosphate remover (most phosphate removed per $ spent). If you like, you can wait to do this until after you've verified significant PO4 levels (ie, > 300 ppb).

Link to Chlorox brand phosphate remover DELETED -- product is HIGHLY diluted, and a very bad deal. Sorry!
Go to http://pool9.net/phosphates/ for current info

Kem-Tek is dropping its own brand, and replacing those products with identical ones bearing a "Clorox" label. Shipping from Amazon is currently delayed, because the product hasn't been distributed to all the Amazon warehouses, yet. There are also some reports of the Kem-Tek/Clorox product not removing what it should. For whatever reason this product seems to act more slowly than some others. Please wait a week before testing . . . but if you find that after a week it hasn't made the expected reductions, please post that info. Remember, only the Taylor phosphate kit can measure semi-accurately above 500 ppb (0.5 ppm).


3. Test your pool water, using a 3:1 dilution of distilled water to pool water. (Use distilled water in gallon jugs from Walmart). Multiply the result X4 for your PO4 level. If your PO4 level is low, you may need to test again, with no dilution. Assuming you find a significant PO4 level, THEN test your tap water, to get an idea of how much PO4 you're adding when you add water.

4. Once you're reading to begin lowering PO4, use *small* doses, and keep and eye on your filter. The pool I worked on has sand filters. DE filters may respond differently. The PO4 remover I used years ago clouded the pool and clogged filters, but I had no such problem this time. However, it may be different with DE, so start small and work up.

5. Meanwhile, maintain chlorine levels . . . and test water temperatures. Let me know what you find. I'm hoping you'll see the same results I did. I still don't think phosphate removers are for everyone, but I am really hoping they may be a solution for pools with recurrent mustard algae.

6. Ironically, solving the mustard algae problem *may* solve the disappearing CYA problem. Mustard algae forms a biofilm; some biofilms 'eat' CYA. It's possible the mustard algae biofilm is harboring bacteria that can eat your CYA.

Let me know; I'm excited!