Cloudy water, high CYA, high TA

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
gglmn

Cloudy water, high CYA, high TA

Postby gglmn » Wed 05 Sep, 2007 18:13

My pool has become a nightmare! Cloudy water all summer long, can seem to clear it. I think my local pool store just wants to sell me more chemicals! I just installed a Hayward Aqua-Rite chlorine generator in hopes of getting it back on track, but I’ve got a ways to go, it’s still cloudy and the generator can't keep up with the chlorine demand.

Temp 86 deg
Ph 7.4,
TDS 2500
CYA 100
Free Chlorine .2
Total Chlorine .4
Total alkalinity 300
Total Hardness 270
Optimizer + 47
Copper 0.1

I also see purple scale on the liner, which I suspect is manganese, I just treated the pool for metals before installing the generator.
I have a Talyor test kit and when I test for CYA, I can’t see the black dot with only ¼” of the tube filled, the 100 mark is much higher on the scale.
I had been using stabilized trichlor 3” tablets and dichlor shock. We also have an autocover so the pool was covered most of the time.
I have recently used Pool Magnet Plus to remove any metals before starting up the salt generator.
I’ve called the Hayward tech line to go over the output of the generator and the tech said it’s working fine, and I should have a chlorine demand test performed.
I have a 4 stage turbine pumping air through drilled pvc pipe to aerate in hopes of bring down the TA.
The filter element is six years old, Sta-Rite 500, and is running at it’s normal pressure, 10psi. It was just cleaned 3 weeks ago.


chem geek
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Postby chem geek » Wed 05 Sep, 2007 19:07

Your use of Trichlor and Dichlor has led to too much CYA in your water -- it sounds like it's way over 100 -- possibly at 150, 200 or even higher. For every 1 ppm FC added by Trichlor, it also added 0.6 ppm to CYA. For every 1 ppm FC added by Dichlor, it also added 0.9 ppm to CYA.

You have an impending algae bloom and your chlorinator is not able to keep up with that chlorine demand. This explains the low FC level in spite of your chlorinator being on so long. You need to shock the pool with extra chlorine -- either unscented bleach or chlorinating liquid, but with the high CYA level it will be a difficult battle.

You will eventually have to do a partial drain/refill to lower the CYA level in your pool anyway so you might as well get started on that since it will make everything easier. As for how much bleach or chlorinating liquid to use, just add as much as you can, but be sure to add it very slowly over a return flow at the deep end and then brush the bottom of the pool where you've added it. If you can shock to 20 ppm FC, that would be OK (not great, but since you have to drain anyway there's not much point wasting too much chlorine you'll end up diluting).

By Optimizer, are you talking about BioGuard Optimizer Plus? That is essentially borates, similar to Proteam Supreme and 20 Mule Team Borax.

At least some of the cloudiness problem is due to the very high Total Alkalinity (TA) since your saturation index is +0.3 (assuming CYA is 200). In fact, I suspect you are having to add lots of Muriatic Acid periodically to keep the pH down, is that right? Lowering your TA via the procedure outlined in this post should help, but if you do a partial drain/refill that should lower the TA as well as the CYA, unless your fill water is high in TA (unfortunately, it will also dilute your salt level so you'll have to add more salt -- and possibly calcium as well).

So start with shocking with bleach or chlorinating liquid and also start a partial drain/refill. With an SWG, you only have to get your CYA level down to around 80 and can live with that if you keep your FC level at 3.5 ppm from the SWG. Do not use any more Trichlor or Dichlor as both add to CYA.

By the way, do you have a cartridge filter? It seems with the high CYA that perhaps you have not backwashed every week.

Richard
gglmn

Postby gglmn » Wed 05 Sep, 2007 22:32

The optimizer is BioGuard Optimizer Plus. I have been slowly relpacing the water by vacuuming the pool to a drain, about an inch and a half every couple of weeks. I have a Vinyl liner pool, how do I do a partial drain/refill? I worry about the liner shifting. I have been adding PH UP which I found out was soda ash, which has added to the TA. I tested a sample of my water supply and it has a high TA, about 270. I installed the salt generator to avoid the tri/di-chlor. I've been adding Muriatic Acid and aerating per that article but I'd like to do the partial drain/refill. I have a Sta-rite 500 cartridege filter, 6 years old. I just cleaned them 2 weeks ago. Any ideas on the purple scale?

Thanks for the help!
George
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Wed 05 Sep, 2007 23:16

You are right that with a vinyl liner you need to be careful with how you drain and refill. There are two options. One is similar to what you are doing now and is called continuous dilution. You essentially drain from one side of the pool while simultaneously filling from the other side. So the water level doesn't change in this situation. The problem with this method is that it takes more water to achieve dilution. Changing half the pool's water volume only results in dilution to 61% of original values (i.e. diluting by 39%). Even replacing an entire pool water volume by continuous dilution only results in a dilution to 37% of original values (i.e. diluting by 63%). So this method is inefficient in terms of water usage.

The other method of dilution uses either a large plastic sheet (larger than the pool) or uses multiple large silage bags. One puts the sheet or silage bags on the pool water and fills on top of the sheet or into the silage bags while simultaneously draining from under the sheet or outside the silage bags. The sheet and silage bags will drop as water fills on top or inside and the total water level remains constant. After the amount of dilution is done, you remove the sheet or empty the silage bag contents (turn them upside down) to mix the fresh and remaining water.

The purple scale might be manganese, but I'm not sure. Maybe others know more about that and what can be done for it. If you have a water quality report of your fill water, look at metals -- copper, iron and manganese.

Richard
Guest

Postby Guest » Thu 20 Sep, 2007 22:07

Here it goes...High CYA levels and traces of copper sometimes combine together and give you that purple dust and the only way to get rid of it is by draining as much as you can without messing up the liner....some times i have had customers drain 2 or 3 times just to get the CYA level down...the cloudiness could be a chlorine demand, when draining the pool that will help also we have a test that we do overnight that tells us how big the demand is and if it is calling for 100 pounds of shock we recommend draining... Say if you drained half the pool that would cut the demand in half..... For a manganese stain it turns the pool black,which usually comes from well water add some sort of metal control and maybe some filter aid to help trap the metals in your filter and backwash out clean filter with a cleaner
Guest

Postby Guest » Thu 20 Sep, 2007 22:09

Also if you have a High CYA level and a chlorine demand it could mask the true reading of the CYA level so your CYA may be WAY HIGHER than what is it reading...If you have a chlorine demand and your CYA level is within range it should read zero in a chlorine demand
Guest

Postby Guest » Thu 20 Sep, 2007 22:13

If you have not had heavy rains you could probably drain to about a foot in the shallow end of your pool refill the pool circulate the pool for 24hours and drain again to about a foot in the shallow end...the circulation is very important !!! you have to let the bad water mix in with the good before you drain again

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