Mustard Algae, 2nd year of battle

[motomom]

Ok. I've decided to go ahead and post, even though I know the answer is probably here somewhere. This is such a great forum and has been so helpful to me in the past. However, I'm going to be hosting a couple of important events this summer (one child's wedding in July and another in August!) and it is going to be important that my pool looks and performs perfectly.

Last summer I battled mustard algae all summer long. I have lugged endless bottles of bleach, vacuumed, brushed, added filter socks, tested (I have one of the good Taylor test kits) and still at the end of the season last year I had the mustard brown silty-looking stuff on the bottom of my pool. I really want to get rid of it this summer. Otherwise my pool is so beautiful, clear sparkly water.

I'm wondering now if my algae problem is being caused by my high ph/TA. I didn't worry about it last summer because the pool is vinyl, and I never noticed any scaling.

Yesterday, I decided I was going to kill that algae if it didn't kill me first. Since the pool is still a bit too cold for comfortable swimming, about 76 degrees, now was the time. Bleached vinyl liner or no bleached vinyl liner.

I put 16 1.5 gallon bottles of 5/6 % bleach from Wally world into the pool. The FC level was high enough that the test in my kit didn't turn pink even with 2 scoops of the R-0870, so was probably over 50.

Here are my numbers this morning.

FC 30
CC .5
pH over 8.0, very pink
Acit demand 9 drops to 7.4
TA is 180
CH is 220
CYA is 40

Now, I have been using only bleach since last summer with one exception. During the winter, which was exceptionally mild here in our part of TX, whenever the water temp would get above 55 degrees or so I would add a powdered shock, Dupont Multifunctional Shock (Sodium dicloro-s-triazinetrione) just to make my life easier and have more time for quilting. I'm getting kinda old to be lugging all those bottles of bleach around, but of course I can't find anyone around who is willing to maintain my pool using only the chemicals I say. They always try to sell me something I don't want.

So, I know I probably have algae because of the drop of FC in my pool from last night till this morning. I will do this process again this evening, until the FC stops dropping. But, and here is my real question, is the high pH affecting this process? Exactly what is bad about a high pH if you have a vinyl pool? Our water is incredibly hard, and always will be. Does this high pH mean that I will always battle this algae?

[aylad]

Wow, I hope that you still have some color left on your liner!!

I'll let Ben, Richard, or some of the other chemists address the effectiveness of the high pH, but just wanted to say that you can't trust your pH readings with your chlorine levels that high. Even with the better kits, the pH will read falsely high when the chlorine levels are as high as yours are.

The dichlor that you used is fine--it has a low pH, and will tend to drop the pH in your pool, but you just have to be careful to watch your CYA levels because it is stabilized and they will rise.

[motomom]

Actually I can't tell that it faded my liner a bit. The pool looks beautiful this morning, nice and blue. Still that little bit of pesky brownish silt that will need to be vacuumed out today.

[motomom]

Wow. I lost 15 ppm over the day. I guess the algae is still dying. I can hear them crying from my back porch!

I just put 10 more 1.5 gal bottles of bleach into the pool, and I vacuumed it again today. I must say it sure looks beautiful and inviting. It is starting to really sparkle. So, question still is, do I add muriatic acid, to try to bring the pH down?

[Watermom]

You don't know what your pH actually is because you can't get an accurate reading when the chlorine is that high.

[motomom]

Ok, just tested FC for the night and it is 45. Even in the moonlight I can see the drain at the deep end. Cool. Will run all tests again first thing in the morning.