How much to drain to lower CYA

WannaBEEPoolgirl

Silver Supporter
Jun 17, 2018
40
Ashburn/VA
Had the pool store open the pool 10 days ago. They came back to check yesterday and adjust and I went back over them because I want to know how safe it is. Well:

FC is 2.6
CC is .6
pH is 7.2 (yay)
CYA is through the roof—over 100. So before I SLAM, I want to lower CYA. How much water should I let out?
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
18,067
Northern NJ
You have to have an idea how much over 100.


CYA > 90 dilution Test
For CYA > 90ppm, repeat the test adjusting the procedure as follows:

  1. Fill the mixing bottle to the lower mark with pool water.
  2. Continue filling the mixing bottle to the upper mark with tap water.
  3. Shake briefly to mix.
  4. Pour off half of the contents of the mixing bottle, so it is again filled to the lower mark.
  5. Continue the test normally from step 3, but multiply the final result by two.
If you need to dilute the pool water further then apply these ratios:

Pool waterTap or distilled waterMultiply result by
112
123
145
Note that when doing a diluted test not only do you multiply the range of the test you multiply the error rate of the test, so results are a ballpark - not an absolute.
 
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zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,437
Houston, Texas
You will need to drain and replace about 80% of the water to get the CYA down to 30 ppm. Would you be using well water or have water trucked in?
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,437
Houston, Texas
Depending on the capacity of your well, you may need to a series of drain and refill cycles to get the CYA down. Is the pool clear or swampy?
 

WannaBEEPoolgirl

Silver Supporter
Jun 17, 2018
40
Ashburn/VA
Depending on the capacity of your well, you may need to a series of drain and refill cycles to get the CYA down. Is the pool clear or swampy?
It’s really clear! I was going to swim in it until I tested. I’ll drain for a little bit longer and then slowly fill back up. It’s only down a two inches in 2 hours.
 

zea3

Mod Squad
TFP Expert
LifeTime Supporter
Jul 10, 2009
12,437
Houston, Texas
Since your pool is clear you can work on draining and refilling over the summer and use only liquid chlorine in your pool. As long as you don't need to slam, you can run the pool with higher CYA, it will just take a lot of chlorine. You can work on replacing your water slowly and as long as you keep the chlorine up you can keep algae away. Whenever a heavy rain is expected drain off some water ahead of time and take advantage of the free water. You may want to consider investing in an SWG. You would only have to drain down to 70 ppm and no lugging bottles around!