First time algea problem

[cmcq]

I just returned from a one-week vacation and have some pea green colored algea on the steps and a few spots where the walls meet the bottom of the pool. Most of it brushes away, but not all of it. The water is still clear. I've never had any algea before, so I want to make sure I do the right things in the right order.

Here are the particulars:

22k gallon inground gunite pool (standard white plaster)
SWG
FC = 3.5
CC = .5
CYA = 60
pH = 7.2
Temp = 82

The punp/SWG was on a timer to run about 9 hrs/day while I was gone and was set to 100% generation. We also left the solar cover on to minimize things falling in the pool while we were gone. I've had the SWG running since I got home this afternoon on "boost", but I don't really have any other chemicals at home right now (shock, clor sticks, algecide, etc).

I suspect step 1 is to bring the chlorine level way up, but the SWG won't get it there by itself. What is the best remedy, and should I add algecide?

Thanks
Charlie

[Watermom]

The best remedy is to just shock the pool with plain, unscented laundry bleach. Try and test your water 3 times a day if you can, and each time, shock it back up to about 15ppm with bleach. In your pool, I think each 3 quart bottle should raise your cl level by approximately 2.5ppm. So, its gonna take quite a bit of bleach in the next few days, but it will kill it. The key to killing algae is a sustained high cl reading instead of letting it yo-yo up and down. Also, run your pump 24/7 while you are trying to clear it up. Also, keep an eye on your ph. You are ok at 7.2, but you really don't want it to go any lower. Keep us posted how it is going. Good luck.

BTW -- if you haven't already done so, check out the pictures in the thread that is stickied at the top of this forum. Pretty amazing what bleach can do for a green pool!

[CarlD]

Do NOT add algaecide--it will only make your problems worse. Chlorine is STILL the best algaecide there is.

If you add an ammonia-based algaecide, you may get foaming. Copper-based algaecide will give you high copper problems.

Even the only algaecide we recommend, Polyquat 60%, is not recommended to KILL algae, but only to prevent it.

Normally, a CYA of 60ppm calls for a shock level of 20ppm of free chlorine, but with an SWG, which by itself demands higher CYA levels, Watermom is probably right about 15ppm as the target, but going to 20ppm won't hurt. You'll probably need to raise your SWG level.

AFTER you get rid of the algae, then add about 1.5 to 2 oz of polyquat every week to help prevent algae.

Every gallon of UltraBleach will increase your free chlorine level by about 3ppm. So if your FC is now 3.5 ppm, you'll need about 4 gallons of it (6% concentration of bleach).

[cmcq]

Thanks. I added 6 quarts of bleach about 4 hours ago. I just retested and the FC is 11.5 and CC is still .5. Does that make sense?

I just added another 4 quarts to continue raising the level and will check again tomorrow before work.

Thanks

[Watermom]

You are on the right track. The goal is a clear pool and a CC reading of 0. The more often you test and each time add enough bleach to shock it back up, the quicker the pool will clear. You will be surprised how fast it clears. Keep us posted how things are going.

[CarlD]

I agree with Watermom. Besides, with a CYA of 60 (that's stabilizer) the "Best Guess" table says you need to shock to a level of 20ppm FC to clear your pool. 15 may well do it, but 11.5 won't.

[aylad]

cmcq,
How's the pool looking? Did you have any problems getting it cleared up?

Janet

[myLABSpool]

Do NOT add algaecide--it will only make your problems worse. Chlorine is STILL the best algaecide there is.



I wish I read this before I just dumped 32oz of poly quat into my 24k gallon pool. Why do you say it will make my problems worse?

[chem geek]

PolyQuat has the least side effects of all algaecides so it's not a disaster that you used it. Mostly, if you add large amounts it will consume chlorine so you'll need to add more chlorine. With PolyQuat, it's mostly that it was not necessary than being a real problem.

PolyQuat is much better at helping to prevent algae, such as when the chlorine gets too low for a brief time, than it is killing an existing algae bloom. It simply kills too quickly to keep up with a full bloom. Shocking with chlorine is the best way to get rid of algae, even if it's a LOT of algae as shown in this thread (http://www.poolforum.com/pf2/showthread.php?t=1180).

Richard

[CarlD]

I wish I read this before I just dumped 32oz of poly quat into my 24k gallon pool. Why do you say it will make my problems worse?

You should have kept reading. Two sentences later I wrote:

"Even the only algaecide we recommend, Polyquat 60%, is not recommended to KILL algae, but only to prevent it."

As Chem_Geek said, the worst it will do is lower your FC to about zero and then you'll have to boost it again.

OTHER algaecides are the problem. They foam or add copper or do all sorts of unpleasant things that make your situation worse. Polyquat doesn't do any of those. Plus it doubles as a flocculant to help clear out the fine stuff that passes through the filter.

[myLABSpool]

Thank you Chem Geek and Carl D. I feel better after seeing your responses. This has been a stubborn run of algae that I had been marginally keeping at bay for the last 4 weeks or so. However in the last week it really got bad so I had to hit it hard. I've added 4 gallons of 12.5% chlorine to 24k gallons in the last 4 days and brushing daily and last night finally with polyquat.

I can attest that the Polyquat must have driven my CL level down, because last night it was well over 12ppm just before I added the poly quat, and this morning it was about 6ppm. Unfortunately I was out of CL this AM so it will have to wait till I get home from work to boost it back up. I'm also hoping to not see new algae growing :)

My numbers this morning are:
FC ~6 (last night 12)
pH 7.8
TTA 100
CYA ~60 (Higher than I'd like, and next year I'll use tablets minimal to keep it low)
24k gallon vinyl.

Thanks