Algae/shock question....

[court475]

We've had some brown stuff at the bottom of the pool that would come right back after vacuuming. I figure it's some kind of algae. I shocked the pool yesterday, had to add 7 of the 3 qt bottles of bleach to keep it at 15 FC. There's no CC. This morning I only had to add one. Should I continue to keep it at 15 today? This was an expensive shock! Also, I kept the vacuum running all night. Should I have done this? Thanks!

[CarlD]

Without a full set of test numbers, it's hard to tell.

Whether it's now dead algae, or still alive, you ought to vacuum to waste instead of trying to filter it out.

Check our stickied threads on cleaning your pool up.

[Watermom]

It also might just be dirt/dust that gets stirred up when you vacuum and then settles back down to the floor. That often is the case in my pool. The installer used tape to tape together the pieces of foam under my liner. When you are looking at the pool liner, you can't really see it but it caused slight "ruts" and the dirt likes to settle into those ruts along the liner floor of my pool. I can vacuum one day and then the next day, the brown "lines" are back.

[court475]

Sorry - here are my numbers right now:

FC - 7.5
CC - 0
CYA - 30
Ph - 8.0
Alk - 210

Added enough bleave a few hours ago to bring it 15, got home from church and it's down to 7.5.

[CarlD]

Your pH is your problem--at 8 it's hindering your chlorine's effectiveness. You need to lower it to 7.2-7.3--which is swimmable.

[court475]

I've always had alk/Ph issues. I got the alk down a bunch earlier this summer by using acid and aerating, and it crept right back up pretty quickly.

[CarlD]

I've always had alk/Ph issues. I got the alk down a bunch earlier this summer by using acid and aerating, and it crept right back up pretty quickly.

Since your CYA is pretty low, and your pH trends high, you are an ideal candidate for...dare I say it?...Tri-chlor tabs! They are extremely acid, which you need, and your CYA can easily tolerate going to 50 or even 70ppm. aylad, one of our mods, lives in Louisiana and she keeps her CYA around 70ppm to be able to have a consistent FC level--she just keeps it in the 5-10ppm range all the time.

We usually advise AGAINST Tri-chlor tabs because you can easily run your CYA up to 100 or more, and your pH down below 6.8--but you have need of the acidity and room for the CYA. Just be sure NOT to get the "double-acting" kind--they have copper in them and you don't want that.

Curiously, this season I have used tabs far more than before--the constant rain all summer keeps washing out the CYA and I just have to watch pH and add Borax from time to time.

IF YOU USE TABS YOU MUST TEST YOUR pH AND CYA LEVELS RELIGIOUSLY AND ABANDON TABS IF pH GETS TOO LOW OR CYA TOO HIGH.

When aylad looks at this thread she can better evaluate it as she lives in a similar environment to you.

[court475]

Thanks so much for the suggestion. I've been pretty frustrated this season, for the first time. Maybe the tabs will help! Do you know how I should use them? Or just follow the instructions? I really appreciate the help!

[aylad]

Courtney,

Where in S. Lousiana are you? I'm up near Shreveport, and my pool is in full sun all day with similar temps and humidity conditions as yours. I have found over the years that keeping my CYA at 70-80 significantly drops my chlorine demand.....I do have to keep a range of 5-10 ppm, but I can do that by dosing toward the high end with bleach and then dosing again about 3 days later, give or take a day....so I only have to make additions a couple of times a week unless something happens that requires me to shock it. I usually keep trichlor in my feeder with the feeder turned to the absolute minimum flow (just to keep SOME chlorine going in daily--that alone only keeps my Cl level at about 1.5-2, and I use bleach as the primary chlorine source and for shocking). As CarlD pointed out,your pool right now is ideal for trichlor tab use, and you probably could get away with using primarily the tabs for the rest of this swim season (ours goes 'til late September, and I presume yours does, too). It will lower your pH, and, although I can't explain the chemistry behind it, may go a long way toward solving your TA problems. You wouldn't need it to lower very much--120-150 works just fine in a trichlor pool. Do you have an inline feeder, or can you get a floater that allows you to dial the flow rate?

In order to determine whether the brown stuff in the pool is dirt or algae, test your Cl at night after the sun is down, then test again in the morning before the sun hits the pool. If you're losing more than 1-2 ppm in chlorine, then it's algae and you need to maintain the shock level in your pool for a little longer. If not, then it's most likely dirt that is settling, and vacuuming to waste or brushing the pool to keep it stirred up in the water so the filter can help get it out are your two best options.

Janet

[CarlD]

Thanks Jan.

Assuming it's not live algae (see Jan's test for it again), then you can go to other measures.

I didn't see what kind of filter you have. If you have a sand filter, you can add a little DE powder to it through the skimmer and it may pull out that brown stuff if it's too fine for the sand to trap it. DE is cheap: I'm using the same $8 10lb box for the 4th season now. About 1/4 to 1/3 cup of DE is enough--just enough to raise pressure about 1lb. If you go too high, just backwash and start again.

If you are using a DE or cartridge filter you cannot do this--it does no good on the DE filter and can clog the cartridge filter and damage it.

You should use "Skimmer socks" or their equivalent in your skimmer--they pull out lots of fine, fine stuff. Anyone can use them and they are cheap. I use them all summer but in the late spring and early summer they pull out tons of pollen that we get here in NJ.

If none of these things work, we'll try the next round of ideas.