The green is gone and yet the clouds remain

santee · Postby **santee** » Fri 20 Mar, 2009 21:06

We had a severe algae growth upon opening the pool 3 weeks ago. We have treated with chlorine to kill it and have been maintaining a no green zone with algaecide, but the water has never cleared. It has been shocked once last week and clarifier has been added to no avail. I am sending my husband out to the shop to get a water sampling, but decided to start the post now. The pool has a DE Filter and is a very large above ground model...32 feet by 16 feet and has a 7 foot depth at one end. The water temp is 65F. We have it on a solar heater, so we have no way of raising it without the sun's help.

I will get back with the chemistry quick like. Thanks for being here. If we can't fix it, it's going away.

santee · Postby **santee** » Fri 20 Mar, 2009 21:32

It'll have to be in the morning. The shop was closed.

Postby **chem geek** » Fri 20 Mar, 2009 22:52

It takes regular addition of chlorine to keep it at shock level as well as brushing and 24/7 filtration to clear the pool. That assumes that it is still cloudy from dead algae and not from improper chemistry (saturation index too high). See this post on defeating algae and when you get your water chemistry numbers you can use The Pool Calculator to calculate the saturation index. However, I strongly suggest you get your own good test kit because pool stores do not always do all of the tests accurately. Get either the Taylor K-2006 kit for a good online price here or the TF100 kit from tftestkits.com here with the latter kit having 36% more volume of reagents so is a little less expensive "per test".

Richard

Guest · Postby **Guest** » Sat 21 Mar, 2009 01:57

If we can't fix it, it's going away

We'll do our best to help.

santee · Postby **santee** » Sat 21 Mar, 2009 13:52

Ok we finally got to a shop and I did buy the giant test kit that does it all.

FC = .5
TC= 2.5
pH= 7.4
TA= 310
CH=540
CYA=100+, not sure what the + means
TDS=2500, it has been suggested we partially drain and refill at this point due to salinity
Phosphates are 0
salinity =2200

We are willing to partially drain if that is needed, since the original fill was 9yrs ago. We do add at least 4inches of water a month because this is the desert.

TIA

Postby **chem geek** » Sat 21 Mar, 2009 14:47

The 100+ for the CYA reading means that it is at least 100 ppm. You can do the test yourself diluting the pool water sample in half with tap water (or distilled water, though that's not necessary since there isn't any CYA in tap water) and redo the test and multiply the result by 2. That will let you measure up to 200 ppm. You could repeat this with more dilution if the CYA is even higher than that.

You will need to do one or more partial drain/refills of the pool (or use the "sheet" method for continuous drain/refill) to dilute the water to lower the CYA level. Higher CYA levels make chlorine less effective so let algae grow. If you don't maintain a minimum Free Chlorine (FC) level in a manually dosed pool of at least 7.5% of the Cyanuric Acid (CYA) level, then algae can grow faster than chlorine can kill it.

Read up at the Pool School to learn more.

You probably were using Trichlor pucks as your sole source of chlorine. With Trichlor, for every 10 ppm FC that it adds, it also increases CYA by 6 ppm.

Richard

santee · Postby **santee** » Sat 21 Mar, 2009 15:15

Thanks Richard,

I will do that. We were using granular and pucks from the shop. I am ready to switch to bleach etc. I'll need to get more info regarding that method. I will read through the pool school.

I am guessing the "sheet" method drains and fills at the same time. Any advice on that?

Thank you so much for your time. I was ready to scrap the thing, but husband really likes having it. Next time we go in ground and low maint ... Ha!

Postby **chem geek** » Sun 22 Mar, 2009 03:23

Yes, the sheet method is where you drain from under the sheet while adding fresh water on the top. When the sheet gets down to the level you want, you remove it. Of course, this needs an awfully big sheet if your pool is large. Some people use silage bags draining outside and filling inside for a similar effect. These techniques use less water than a continuous drain/refill while still letting you drain up to the entire pool safely.