Draining pool due to CYA and light stain on liner.

Jason.H.

Member
Aug 19, 2020
6
North Carolina
Hello everyone, we just moved to a home with a 28k gallon chlorine pool. Previous owners have owned the home and pool since 1994. Water is clean and clear, equipment seems in good shape and we love it. Now for the not so great, previous owners always used 3" chlorine tablets so the CYA is too high causing me to have to keep the FC too high. I've drained about 20% of pool and refilled a couple times now with well water (which previous owners said they have always used). CYA is now down to 100 from 170. A couple more drain and fills and should be close. Is it ok to turn valve to bottom drain only and use pool pump in waste to drain pool down? This is what I've been doing and hope I'm not damaging anything. Also seems like I have a light brownish stain on liner in shallow end. It doesn't feel slimy and doesn't change when brushing it. I don't think it was there when we first got the pool 3 weeks ago.

When we first got the pool FC was close to zero from the chlorinator running out of tablets, PH was below 6.4, TA 30, CYA 170+ Since we've taken owner ship I have stopped using the tablets and use 10% liquid chlorine to keep FC close to 10ppm, CC .5ppm, with CYA currently at 100 (working on getting it lowered). TA 70 PH 7.4 (adjusted with baking soda and borax). Water temp is currently 80 degrees F. Seems like the stain hasn't appeared until I started trying to balance the water. What should be my next step? I can't SLAM until I get the CYA lower, we're getting a ton of rain today so will be prime time to dump some water out of the pool again tomorrow and refill. I'm not sure if the stain is algae, iron, or something else, see no cloudiness in water or cloudiness coming off of stain when brushing. Seems like on a hot sunny day the stain almost disappears but could be my eyes lol.

Thank you for this wonderful site, I've never owned a pool and had no clue about any of this until 3 weeks ago.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Welcome to TFP! :wave:

Is it ok to turn valve to bottom drain only and use pool pump in waste to drain pool down?
Sure.

Also seems like I have a light brownish stain on liner in shallow end. It doesn't feel slimy and doesn't change when brushing it. I don't think it was there when we first got the pool 3 weeks ago.
Could be iron staining from that well water. Try rubbing a Vitamin C tablet on the stain. Does it go away? If not, then the stain may be organic.
 
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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Just a basic Vitamin C tablet would be best. Ha. Testing well water ... not really. Sometimes you can take a fresh water sample (from the source not pool) to "try" and get a decent iron level, but it's not accurate. If you take a pool sample, the chlorine might skew the reading a bit.