Green Algae in IG Pool

I've browsed this forum over the last few years since we put in a pool and have learned a lot. For background ... we have a 10,000 gallon inground gunite pool with an 8' spillover spa, AquaRite salt chlorinator, 2-speed pump & solar panels.

As of earlier this week, we had our first major problem -- a perfectly green pool. I immediately went out and brushed the entire pool/spa as best as I could and then added liquid bleach (& acid because our pH was high).

During swimming season I monitor the chemical levels frequently, however over the winter months things slipped. I wasn't monitoring the chlorine because I thought that since the temperature was so cold we wouldn't have any problems. We do have a salt chlorinator, but it doesn't generate chlorine when the water temperature drops below a certain level (I think it's around 55 degrees). Over the last few weeks it has started warming up here and the water temperature has been in the low 60's, and I should have been more diligent about checking the pool, but wasn't. So, I assume that's how the green algae started to grow.

Our current readings are:
Chlorine: 15ppm
pH: 7.2
Total Alk: 80
Calcium Hard: 200
CYA: basically 0 (I need to add, but need to get some first)

The chlorine level has been @ 15ppm for two days now and I've been running the pump 24/7. The green algae on the bottom of the pool and walls actually cleared up right away when I added the chlorine. Keeping the chlorine level high has made the algae disappear to my *naked* eye -- but I suspect it's still there.

I've got a couple of concerns ...

1. When I brushed on the 1st day that I noticed the green growth, since the walls are not perfectly straight and there are alot of curves, I couldn't get all of the areas brushed well (or even at all in some places). Is this going to be a problem once I lower the chlorine to the standard level?

2. How long should I maintain chlorine at 15ppm? It's been 2 days so far.

3. From here on out, as long as I maintain the chemicals properly should everything be fine, or will there be some other related problems from this algae outbreak?

Any comments are appreciated - thanks!

Yes to adding some cya. In the meantime, watch your cl closely or you'll end up with another algae bloom. Do the best you can with the brushing. You can only do what you can do. Ideally, you should maintain the high cl level until you no longer have a CC reading. You didn't say what type of kit you have, so you may not be able to test for this. If not, then I would just suggest maintaining the high cl readings for at least a couple more days just to be sure you got it all. Then, you can let it drop some. I would also suggest adding just a little Borax and bumping your ph up to about 7.4. If you maintain your chemistry, you shouldn't have any further problems. Hope this helps.

Watermom

Thanks for your info, watermom! I use the Taylor K-2006 Complete FAS-DPD chlorine test kit, but since I'm ready for new reagents I'll be checking into Ben's kit. I don't normally check the combined chlorine, but I just did and it is 0 -- so I guess that's a good thing.

I wasn't sure if it was okay to add the stabilizer right now or not, because on the stabilizer package it says to get the chlorine in the appropriate range first -- since I'm shocking it right now and the chlorine level is so high I didn't know if I'd be screwing the chemicals up in my pool by adding it now.

Without any cya in there, your cl level is going to fall back down pretty quickly anyways. Go ahead and add some tomorrow. Add it to the skimmer while the pump is running and then wait a week or so to allow it plenty of time to dissolve in the filter before you retest for it, add more or backwash. Shoot for a reading of about 30. 30-40 is a good level for most people. For the next few days until your cya starts showing up in the water, you'll have to watch your cl level pretty closely to make sure you keep a cl reading. Don't want green water again.

Watermom

Ok...I have had a pool for 3 years now. Basically been on my own on learning how to regulate it. I have been told that a saltwater system is so easy, yet each year I have algae. This year is no different. Uncovered the pool and there is the nice green color of the pool. What should my next step be? Should I get the chemicals set at the correct setting or just backwash and suck the crap out for the next couple of days? Currently I have the system set on super chlorinate in an attempt to kill the algae. Any help would be greatly appreciated.

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Originally Posted by Blackston

Ok...I have had a pool for 3 years now. Basically been on my own on learning how to regulate it. I have been told that a saltwater system is so easy, yet each year I have algae. This year is no different. Uncovered the pool and there is the nice green color of the pool. What should my next step be? Should I get the chemicals set at the correct setting or just backwash and suck the crap out for the next couple of days? Currently I have the system set on super chlorinate in an attempt to kill the algae. Any help would be greatly appreciated.

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Welcome to the forum.

First of all you need to remove all debris, leaves, etc. from the pool manually before you start circulation.

Empty your pool pump basket, and reseal the O-ring with Magic-Lube.

Start the circulation using the skimmers only. You need to shut down the SWG as you are wasting cell life trying to clean up your algae.

Start vacuuming to waste the stuff at the bottom of the pool. Refill with softened water if possible. You will have to shut down frequently to clean the pump basket, and probably backwash the filter.

Start adding regular bleach to bring up the chlorine level up to 15 ppm, and maintain it until the algae has diminished and the chlorine level starts to rise. With a vinyl liner don't go higher than 15 ppm or you can start to bleach the liner. You will have to vacuum as well, as the dead algae settles on the bottom.

If the water is cloudy, shut the circulation off, but continue to add chlorine round the edges. This should help the dead algae to settle making it easier to vacuum.

Back off on the bleach, start adding CYA, Muriatic acid, Baking Soda, and Borax as necessary to bring the pool chemistry in line.

Once the chemitry is in line, backwash the filter once more, and then start the SWG at the setting you normally use and monitor the system daily for a week.

Post your Water analysis so we can be more definitive in our advice.

Hope this helps.

Pat