CYA / Algae question

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jandersen13

0
Feb 27, 2015
180
Grand Rapids MI
I just opened the pool 1 week ago. It was clear and things are looking good so far. We had a cold spring here in Michigan, which helped the pool not turn in to a swamp. Chemical balance looks good, with the exception of CYA. Here are my numbers from the TF100 kit (got a new one this year to replace my last, so everything is new).

FC - 8
TA - 130
PH - 7.2
CYA - 100+ (I haven't done the diluted test yet, but assume it's higher)

I normally use the pucks in a chlorinator, which I know is not recommended here. I've owned the pool for 5 full seasons, this being the start of the 6th. I used to drain almost half of the pool each closing in the fall (below the return lines and deep end is only 6 feet deep), which helped me to replace enough water to remove CYA to zero over the cold winters here in Michigan. 2 years ago we got a new vinyl liner, which also has the liner over the steps in the shallow entry. The pool company says we should not drain like we used to any longer to prevent the steps from getting messed up. Because of this I don't have water replacement to reduce CYA over the winter.

My question here is, the water looks great right now. But that seems temporary with CYA being high. The water temp has been 58 degrees since opening last week. Do you expect algae to take off as soon as the water temp rises?
 
Not necessarily, if you keep your FC above 8% of your CYA at all times you won't get algae. CYA doesn't cause algae, having too little chlorine to offset the CYA does. So if your CYA were actually 100 then your target would be 11-13. If it is actually 150 (entirely possible) then you would want to keep it closer to 20 FC. Don't forget that the pH test becomes progressively more unreliable as the FC rises above 10, so that's going to become more difficult/impossible to keep a good read on the pH. It reads higher than the water really is. Not a good thing for a new liner, acidic water can be damaging to it. Also destroy heat exchangers.

Realistically you are going to need to reduce your CYA. This can be done with small water changes so that it doesn't go below your steps. If you put a sump in the deep end and fill from the shallow end (with your filter pump off) you can do it without draining at all, though it will probably take quite a bit more water than if you were able to just drain some and refill. However it is done, the sooner it is completed the better.

This would be a good reminder that your chlorination method is unsustainable and is going to need to be rethought. Liquid chlorine dosing would work, as would switching to saltwater. Pucks without the ability to do regular water changes though is not an option.
 
Can't really say without knowing your actual CYA, but even then the dilution variable makes it difficult to calculate. The answer is a lot though, especially if you aren't dropping the pucks cold turkey.

No idea on the steps, I've never dealt with lined steps. With any liner though you can end up with wrinkles if you do it wrong, so you may want to ask the installer.
 
First do the diluted cya test to see what you have. Then determine how much of the water needs to be changed out. Steps aren't a problem for a day but longer term isn't recommended as the liner can slide.
 
Just did the diluted test and I'm getting between 100 and 120. If I assume 120 then I need to drain roughly 70% of my pool correct? I am thinking of switching to a SWG right now, and if that is the case I need to have the CYA at 70 I think. So in this case I would drain roughly 40% of my pool correct?
 
Get a RJ60 PLUS HERE by selecting the link for the RJ45 and upgrading for $10 to the RJ60 PLUS. Get the chemistry in line and call it done. You will be very happy not dealing with FC on a daily basis. You will need THIS to monitor the salt and nothing else comes close to this test kit.
 

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