Cyanuric Acid Too High

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M

mthorwart

Member
May 6, 2019
12
Penndale, PA
Opened the pool. Had initial high chlorine usage. (Couldn't keep FC overnight.)

Was waiting for chemicals. Just tested the CYA levels, and they exceed the 100ppm max of both my test kits. We had this issue last year, which is when I switched to liquid chlorine...period. I knocked the CYA down then, but not far enough apparently. No more pucks or dichlor for this guy!

PH 7.4
TA 180 (high)
FC 2
CC high (I quit adding drops at some point, since I knew I had issues)
CYA 100+ off scale

18000 gallon, in-ground.

I'm assuming drain and refill is my best option. Vinyl liner, so I'll take it down about 30-50% refill, mix it up and do again.
I know each time, I am getting less bang for my buck percentage wise, but need to knock it down somehow.
Thoughts???

Thanks!
 
Thank you!
I've got a Taylor K-2006 and a Pentair CYA test kit. Both were high. I'll run a diluted solution through and see if I can nail down the actual reading. Read the Pool School book last fall, and will reread as soon as I can.
 
With a vinyl liner pool you do not want to drain more than 18" or so at one time. If you have really cheap, accessible water, that works.

If you want to exchange the pool water with fresh - consider this.
You can exchange some water without draining.

If you place a low volume sub pump in the deep end and pull water from there while adding water in the shallow end (through a skimmer or into a bucket on a step so you lessen the water disturbance) you can do a fairly efficient exchange. That is assuming the water you are filling with is the same temperature or warmer than your pool water. If your fill water is much cooler than your pool water, then switch it. Add the water to the deep end (hose on bottom) and pull water from the top step.

The location of the pump and fill hose may change if you have salt water, high calcium, etc.
In my pool, with saltwater and high calcium when I drain, I put the pump in the deep end and hose in shallow end. The water in the pool weighs more per unit volume than the fill water from the hose.

Be sure to balance the water out and water in so the pool level stays the same. Also be sure your pool pump is disabled during this process. Once started do not stop until you have exchanged the amount of water you wish.
 
Thank you mknauss!

OK - with a diluted test I got a reading right around 110 (55 times 2 for dilution). I'll confess my accuracy may be off...new test kit.

I'm in the process of pumping it down about 12 inches, which will put the water line right around that 18 inches of exposed vinyl. I'll refill it then, and also look at the exchange method you suggested. Tap and pool are about the same temp now, density should be 'similar' at this time of the year so it may not work.

City water is relatively cheap. I'll feel it in the bill, but I don't want to fight the chemistry again this summer. (Feel really stupid that I never put 2 and 2 together on HOW MUCH stabilizer is in those pucks.) Couple of bucks now, for easy when it's warmer - I'll take that.

By my math, removing and replacing 30% of the water gives me a 30% CYA reduction. (100 goes to 70) I'll need to do it 3 times to knock it below 40.

As I do that, I'll add 3ppm of chlorine daily until I get CYA lower. Too cold for algae right now, and no one would swim in 58 degree water anyway.

Appreciate the assist!
 
Remember to factor in that each time you add water back to the pool, the entire pool then is mixed. So you will need to use quite a bit more water doing the 12" drain and refill multiple times.
 
It is not going to do you much good since your putting all this new water in. I would keep it off so you can be sure to properly mix your water with brushing or running a robot.
 
Well, first partial drain and refill completed. I was a little aggressive with the drain part (because I lost track of time), but I filled it back up immediately. Ran the filter for a couple hours with the robot in there. Measured CYA came down to 60...using the dilution method for testing (50-50 with tap water). I drained again and am refilling now. This time I was careful and didn't pull as much water off, and left the robot moving around the bottom the whole time to keep the water mixed. Hopeful this will get me to a CYA of 45ish and I should be able to test without dilution.

At that point, I'll need to decide if I do the whole thing again - or live with the CYA on the high side this summer.
 

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40-50 ppm CYA is very manageable. In fact, your pool will lose 3-5% CYA each month. Backwash, splashout, and a bit to oxidation.
 
Today's numbers:
CYA 40-45 (I got a second test from Leslie's, who said 35. Getting liq chlorine anyway.)
FC 1.0
CC 0.6
PH 7.4
TA 130
CH 100
Phosphates 0 (or nearly so. I have a test kit and tested with the rest.)

Looks like I am in better shape. Will boost the FC up to 5 - 6 which should be in line with my CYA readings.

Thanks for the support along the way.
 
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