Sorry--my CYA is 99. I have a Jandy 1400 SWCG. My pool won't hold any chlorine, I added 1 lb of power powder plus (Leslies product) this evening and I will see if I get any chlorine reading in the morning. I really don't want to have to drain water from the pool and replace it since I am on a well for water, when we have filled the pool we have used a pool water company and hope to not have to incur that additional expense this season. Is a reading of 5 for nitrates really something that would cause a problem?