Algae - need a primer!

Please help me figure this out. We have a 29K plaster inground pool. We've been getting a lot of rain lately and the chlorine feeder wasn't high enough, nor were we running the pump long enough. Anyway, we seem to have some algae growing on the sides of the deep end, in large patches. It's sort of yellowish-tan. Hubby was saying there were stains but I didn't see anything obvious until today, since I don't swim until early evening.

What do I do next? Please give me the whole plan for eliminating this stuff as cheaply and easily (I know, ha!) as I can.

1. How much bleach do I need and when do I add it?
2. Do I need any other chemicals besides household bleach?
3. I am going to have someone else clean my filter, after we do the shock treatment. I thought backwashing and cleaning were the same thing but I was wrong - should I backwash it before the cleaning or is that wasted effort?
4. We're going on vacation in a week, for 10 days. How can I keep the pool from turning while we're gone?

Thanks a ton - I can attach photos if you'd like. Hubby says the stuff is slimy, if that helps. The water itself is still clear, but the stains are visible.

Do you have any accurate test result numbers that we can advise accordingly?

Having accurate test kits are the first thing you should have. :)

You need to post your pool chemistry numbers for anyone to advise you on getting rid of the algae. Include free chlorine, combined chlorine, cyanuric acid (CYA), calcium hardness, pH, and total alkalinity. CYA is particularly important.

It sounds like you have mustard algae which can be pretty tough to get rid of. The treatment is simple. Raise your chlorine to shock level, test the chlorine 3 times a day, and return it to shock level after each test. Repeat this until the free chlorine level holds overnight and the visible algae is gone. Your shock level is a function of your CYA level (see here).

You can get rid of this algae and keep it away, but it will take diligence and patience.

Thank you very much. My son was supposed to have been testing the water but I think we let the levels get away from us this week, what with the rain, the heat, and more sunlight. It wasn't as bad as it is today, and I basically never noticed, and thought hubby was seeing things when he told me there were some new stains.

I will get the water tested tomorrow at the pool supply store, and have son do it with our kit too. Hubby wanted to buy some shock tonight, so we did. I resisted the salesman's pitch for algaecide, though. Do I need the algaecide if I'm already shocking? That stuff is EXPENSIVE!!! We did buy a wire brush and hubby is out there brushing the walls and floor right now. Is that OK & a good thing to do?

Why is CYA level so important? I know you are not supposed to get that number ultra-high, or you have to drain off water to get rid of it.

Do you think I will be able to get this at least under control and then be able to leave it for a week?

Son just told me that CYA level is 100. I"m going to do the test myself to see what is going on. Now, bear in mind we have just added 1.5 lbs. of Zappit. (I know, but hubby wanted to do something right away, and I didn't have enough confidence in the strictly bleach method until I get the info. from you guys.)

Thanks.

Also: What does "Vacuum to waste" mean? We have no vacuum mechanism, only a Polaris. I can run the Polaris with a fine mesh bag, but I don't know if that will actually clean out the algae.

One more question - We have an ozonator (electric) on this pool. Please advise if that makes a difference in the treatment from here on out. I think it's still working...NOPE! Its little blue light is out. Now what???

With a CYA level of 100, your shock level is 25 ppm. Shock as I described in my first post until the chlorine stays at the same level overnight. To clear this quickly, it's very important to test often (at least 3 times a day) and keep bringing the pool to shock level after each test.

Keep brushing; the more the better. If you don't have a manual vacuum, the Polaris may help some.

Thanks, Kurt! No, we don't have a vacuum. I will test the water first thing in the morning - I see that several things getting out of line allowed the algae to gain a foothold. I'm going to take the water to the supply store of the company that built the pool and put in the ozonator. Other than selling me chlorine, they've been pretty good with advice - not trying to up-sell me like the Warehouse Pool guys always do.

Do the shock granules also add more CYA to the water? I have the in-line feeder also and the dial up to about 4. I realize that most of y'all do not ue the pucks and maybe after this is fixed, I will have the confidence to go with just the BBB method.

Is there NO way to lower CYA other than draining the pool? If I don't add any more tri-chlor, will the level eventually drop on its own, what with rain, adding non-chlorinated water, etc.?

Thanks a lot for your help!

Quote:

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Originally Posted by heymom1

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Do the shock granules also add more CYA to the water?
If it's di-chlor, yes. If it's calciun hypochlorite, no.

I have the in-line feeder also and the dial up to about 4. I realize that most of y'all do not ue the pucks and maybe after this is fixed, I will have the confidence to go with just the BBB method.
Overuse of pucks is what got you here. Why would you be confident in the very thing that caused the problem?

Is there NO way to lower CYA other than draining the pool? If I don't add any more tri-chlor, will the level eventually drop on its own, what with rain, adding non-chlorinated water, etc.?
It will go down on its own through splashout but that will take a long, long time. The good news is that you can live with the high CYA. One you get rid of the algae you'll just need to keep your free chlorine between 8 and 15 ppm.

Thanks a lot for your help!

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Good luck.

OK, I understand. Good news - the algae is not visible this morning. I haven't run a test yet, but all I see is some residue at the bottom of the pool. The Polaris hasn't run yet.

When the pool was first filled, and we got the "pool school" lesson, I did wonder about the weakness of the system that included an element that only increased and could not be removed except by pool drainage. That seemed a little ridiculous to me. But we've had very minor problems with the system as is - the ph got out of whack a couple of times with rain, or we'd run out of chlorine in the feeder but catch it before anything happened.

Even this time, I could have caught it earlier had I noticed what dh was saying...He's been saying something about stains for a week now but I just blew it off. And dear son hasn't been testing like he should, even though we have a nice 6-way kit. I will order Ben's kit when it's available again!

So what DO you do if you go out of town, and you aren't there to add bleach?

1. You can run the chlorine up to shock level and hope for the best.

2. You can use tri-chlor or di-chlor in a chlorinator.

3. You can get a friend to stop by every other day and add a bottle or two of bleach.

I prefer to manage my CYA so that I can use option 2. That is, have the CYA below 40 ppm when I go on vacation so that use of tri-chlor doesn't take it too high while I'm gone. I'm not always that good so I then resort to option 3. College-aged kids of friends and neighbors work well for this if you don't have family nearby to help. They're always looking to pick up a couple of bucks and some of them are responsible enough to follow simple instructions.

Kurt, I will probably have to go with option 1 this time. We have no nearby teenagers or college students - only friendly with the neighbors, not friends. My FIL can come by and check on the pool but he can't come every night to add bleach. The CYA is high, around 90, but doesn't that just mean that the chlorine will stay around too?

The kids were in the pool just now, and the CL is probably around 8-10, according to the scale on my little test kit. It's a darker shade of yellow than 6, but not orange or anything.

Ph is about 7.3
No hardness
Alkalinity 100 ppm

Thanks again for the help. You guys are wonderful. I can post a photo now that we have a digital camera.

If the algae is gone by then and you're just going to be gone a week, you could just leave your pool at shock level (25 ppm) and then have your father-in-law come over on the third or fourth day and add three or four 4 gallons of bleach. Three gallons will increase your chlorine by about 6 ppm and four gallons will increase it by about 8 ppm. Even if the pool uses 3 ppm per day, you'll return to a pool with at least 10 or 12 ppm which is adequate for your level of CYA.

Kurt, do you know anything about ozonators? I noticed mine isn't working - the UV light isn't on, and it's too coincidental that it would go out and now we get algae for the first time. I'm sure that the chlorine level was the main problem, but that ozonator does help. I don't think pool stores carry the UV lights so I guess I have to send for one from the company.

I think you said it was still safe to swim in a pool with a 25 ppm cl level?

Quote:

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Originally Posted by heymom1

Kurt, do you know anything about ozonators? I noticed mine isn't working - the UV light isn't on, and it's too coincidental that it would go out and now we get algae for the first time. I'm sure that the chlorine level was the main problem, but that ozonator does help. I don't think pool stores carry the UV lights so I guess I have to send for one from the company.

I don't know anything about them except that the ones that are usually sold to homeowners are generally not very effective. And I know you don't need it. If it were me, I wouldn't bother replacing the lamp.

I think you said it was still safe to swim in a pool with a 25 ppm cl level?
No, your shock level is 25 ppm. Acording to the Best Guess Chart your minimum free chlorine level is 8 ppm and the maximum is 15 ppm. You should only swim when the free chlorine level is between those two numbers.

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Is your water clearing?

Yes, the water has been clear since the first shock. No sign of the algae returning, but I'm going to keep the CL level high and dump some more shock in before we leave town. The water has never been murky - just the yellow slime on the pool walls, and that was gone the next morning after the shock.

but we did have a funny incident yesterday afternoon.

Younger son comes running inside after checking the pool "Something is really wrong with the pool! There's a big green blotch in it!" Older son runs outside to check...He comes back in after a few minutes, with a smile on his face.

The light green pool umbrella had been blown into the pool and was sitting on the bottom.

The algae returned while we were out of town. Since I had the filter cartridges cleaned before we left, I'm just going to have to battle it away step by step. Raised the cl level back up with some Zappit and now the algae isn't visible. I'm going to order a test kit today.

My FIL actually came by twice and if I'd known he was going to do that I'd have asked him to dump in some bleach! Next time...