Black-Mustard

JayBee123

Member
Jun 22, 2024
10
Phoenix, AZ
DE Filter. 20000 gallon pool Phoenix AZ where its over 100 degrees all summer. Can not drain the pool this time of year as the heat in Phoenix would damage the surface.

Total chlorine about 2ppm
Free Chlorine about 3ppm
PH 6.8
Total Alkalinity is ok at about 140 ppm
CYA 158ppm
TDS 5000 ppm

Gosh where to start. A bit of algae showed up about 2 months ago, thought I had it under control with shock and copper algaecide. But poor water quality is not allowing chlorine levels to rise up enough, even using 15 trichlor tabs a week, barely getting to 2 or 3 ppm. The water is basically clear, like surprisingly clear....but black algae continues to be prevalent on the walls and there are large areas of "stuck on or stained on" yellow or greenish algae on the floor. Pool service company has been fired as they have not worked hard enough to solve this. I have everything I need to service the pool myself. DE, vacuum, chlorine tabs, shock, brush etc. Back to square one and need an approach that might at least keep things from getting worse. It's Phoenix, so it's always hot this time of year so can't imagine I can eliminate the stuck on-stained on algae. Put in about 4 pounds of baking soda to get PH up but no improvement yet. Been brushing frequently and running filter almost 24-7. Should I use a metal wire brush on the stains?

Was thinking maybe 6-8 pounds of Cal hypo shock, wait 24-48 hours then maybe more copper algaecide? I could really use a step by step approach here. Like what to put in first, then do I brush or vacuum or backwash before adding something else etc. Should I keep using the baking soda? Do I wait a certain time after adding one thing and before adding another? etc etc. HELP!! Thanks so much for any insight.

Jay
 
You need a proper test kit. I suggest the TF-100/Pro or Taylor K2006C. A proper test kit is needed to get the accurate water chemistry results needed to follow the TFP protocols.
Once you get the kit, you need to run a full set of tests and post them here.
IF the CYA is nearly that high, you need to exchange your pool water. Anything you do right now will not work, or will only work temporarily.
Read Draining - Further Reading

With your high TDS and warm fill water, the exchange will be quite efficient.
 
This was about a week ago. Free chlorine is now up to 2ppm and total is up to 3ppm. PH is down to 6.8 due to all the trichlor. I'm just trying to keep the pool swimmable for summer and not get too much worse. What would be a plan of attack?
 

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We do not provide guidance based on pool store testing. We request the member to obtain a proper test kit and do their own pool water chemistry testing.
 
IF the TA you report is correct, the pH will rise on its own quite quickly. No chemical interaction is needed.
 

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With a TA of 140, which is very high, the pH cannot drop without the addition of acidic products, which are also lowering the TA. So quit adding any acidic products (includes trichlor) and the pH will rise.
 
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