Green Pool (Algae) Re-Occurring..Pictures

by Bryan
(Phoenix, AZ)

I drained my pool (23,580 gal) in May this year. Gradually, the pool went cloudy, to dark to green.

I tried balancing, shocking and algae removing chemicals (Green to Clean/leslies pools, a second product/home depot; this product kills algae and then drops to bottom where the dead algae is supposed to be vacuumed up bypassing backwash.

None worked.

August, 10 days back, I completely drained the pool. I then backwashed (about 10 min). Then added water conditioner and shock; per Leslie's Pool directives and pool water testing.

Now, the pool was crystal clear and beautiful. However, within the next 2 days the water began clouding again!

So, I go back to Leslie's. They tell me that I should try replacing the sand in my sand filter. O.k., but I did that 2 seasons back and supposedly sand should not need replacing that soon.

So, I talked to another pool supply store while pricing the sand. They say that I should not replace the sand and should purchase their algae treatment products.

Pool info:

Shasta Pools built 1996. Pebble tech surface, pop-up suspension cleaning system, American Products 6.5 Eclipse sand filter. The system also has a 1996 Vision V-40 inline cartridge filter that is being bypassed because I'm unable to find the right sized O-ring replacements.

Any feedback is appreciated.



Thanks for the questions Bryan

I've been in many backyards in Phoenix. Mesa, and Tempe to see pools like this one. We'll start from your first paragraph and work down.

If you're going to drain your pool, I would encourage you to do it a bit earlier in the season. You're first removing about 200,430 lbs. of water off the pool (8.5lbs. per 1 gallon of water X 23,580 gallons). Only do this when you need to, maybe every 5 years or so or when the pool becomes so saturated with chemicals.

2nd, because you don't want the Pebble Tech to be baked by the Arizona sun for too long. You want it a bit cooler when you drain the pool.

I would highly encourage you to get a Taylor Reagent FAS-DPD K-2006 pool water test kit. It's the best on the market and will give you the most accurate pool chemical readings.

Pool Water Testing Kit..Balance..Chemistry

Swimming Pool Water Testing..Chlorine..pH..Alkalinity..Care..Kits

Next, you need to shock your pool with liquid chlorine (sodium hypochlorite). Don't use the granules (calcium hypochlorite) because you have hard water and cal. hypo. contains calcium. You'll just be adding more hardness to the water. Here are the links to the charts for shocking your pool:

Swimming Pool Chlorine..Chemistry..Pool Water Care

Swimming Pool Shock..Pool Chlorine..Pool Care..

When I was doing pools and saw a pool like
yours, I would always add an extra 1/2 - 3/4 gallon of chlorine, just to be on the safe side. It's better to over-shoot and have the chlorine at 15ppm or so, than not have enough.

Another good swimming pool chemical is Dichlor, or sodium dichloroisocyanurate. It is a granular, stabilized, and fast dissolving form of pool chlorine and is often used as a pool shock.

While Dichlor does add pool chlorine it will also increase your CYA (cyanuric acid) level while lowering your pool water pH level. Take care in using Dichlor as your CYA can get out of hand very quickly. CYA is the stabilizer for the chlorine.

Chlorine Tablets..Swimming Pool Chlorine..Pool Tabs

The FAS-DPD test kit will have the test for CYA. This needs to be kept between 20ppm - 40ppm.

After you shock the algae will turn a lighter shade of green, then white. This means the pool algae is dying or is dead. At this point your chlorine level will be low because the chlorine was used up be killing the algae, the sun and heat, and the lack of CYA. You should manually dose the pool with chlorine and use a good algaecide to keep any more algae from forming. But remember, algaecides are used for preventative maintenance and is not to be used to kill algae, only chlorine can do that. If you keep your chlorine level between 1.5ppm - 3.5ppm, then you won't need any pool algaecides.

Blue-Green Algae..Swimming Pool Chemistry..Care..Problems

Swimming Pool Algaecide..Algae..Green Water..Cloudy..Chemistry..Care

Keep filtering 24/7 and backwash once per day until the water is clear. Stay on top of the chlorine readings and be sure they don't get below 3.0ppm during this process.

Once the water clears up you'll probably have dead algae on the bottom. If you have a Multi-Port Valve it probably has a WASTE setting on it. You can vacuum the algae to WASTE, bypassing the filter so it won't get clogged with algae, but keep an eye on the water level. It will drop and you'll need to add more water.

Again, algae treatment products such as algaecides are used to prevent algae, not get rid of it. A good pool shock will do that.

Before you shock, try to get the pH level down to around 7.0ppm. Chlorine a more active at this level.

Swimming Pool pH Levels..Chemistry..Alkalinity..Care

Remember that pool chlorine is only as good as the CYA stabilizer. Get the CYA up to 20 - 40 and keep the chlorine level between 1.5 - 3.5ppm. Use a pool tab float; don't put the chlorine tablets in the skimmer.

Hope this helps and I'd like to see your "after" pictures.

Best of luck


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