Why is Cyanuric acid high in a newly filled pool? What can we do to lower it?


Mar 24, 2019
Hi, Our pool was finished with River Rok plaster and we are filling the pool with hose water. I tested the water coming out of the hose and the Cyanuric acid reading is zero. I did this twice to be sure. When I test the water in the pool the reading of Cyanuric acid is 250! (also checked several times) and we haven't added anything to the water or the pool. Why is this and what can we do? All I read online is to replace the water but the water we are filling with doesn't have any cyanuic acid in it. Is this normal for a fresh plaster finish? Thank you

Values of hose water: FCL 0, TCL 0.5, Alk 40, pH 7, TH 0, CyA 0
Value of water once in pool: FCL 0, TCL 0.5, Alk 240, pH 9, TH 0, CyA 250
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