We have a 2500 gal in ground hot tub that is 20 years old. It has a Pentair high rate commercial sand filter and pump. I am having an issue with the combined chlorine building on me. I will change out the water with new incomming water that has 0 combined chlorine in it. I can then let it circulate for a couple of hours in which it will turn over about 8 times. When I retest the water my combined is already at .5 with no bathers. If i let is run overnight my combined with elevate and be over 1.0 in 24 hours. I am feeding liquid chlorine through a Strantrol controler and keep the level at about 4ppm. My pH is at 7.3 and I use CO2 to regulate that. I have added a swim spa Ozonator that is sized for the pool and have it running into the feed lines after my heat exchanger. Since that did not correct the problem I have now added Potassium Monopersulfate. Even after shocking with the recommended dose I have a combined Chlorine level of 1.2 after 1 night. I am using the R-0867 Deox Reagent to give me the correctl readings in my DPD tests.
Anyone out there have any insight that will help me to control or fix this?
Anyone out there have any insight that will help me to control or fix this?