Chlorine Level Won't Come Down

[ray_c]

I have noticed the chlorine level has been staying high in the pool despite not shocking or adding tabs to the chlorinator in a couple weeks. I have been waiting for it to come down, but it just is sitting between 8-10ppm. I also use nature 2, so I usually keep it much lower. The pool is clear, filters 8 hours a day, and is used at a moderate level. I confirmed the reading with test strips and by taking a sample to the pool store.

Is there a reason why a chlorine level would stay high for a long time like that?

thanks,

Ray

[chem geek]

Do you have a pool cover or is the pool not exposed to direct sunlight? Have you been using any non-chlorine shock (potassium monopersulfate, MPS)?

[ray_c]

Do you have a pool cover or is the pool not exposed to direct sunlight? Have you been using any non-chlorine shock (potassium monopersulfate, MPS)?

The pool is exposed to sun. I do not use a cover during the season. I do use MPS as part of the weekly routine.

[chem geek]

MPS will usually show up as Combined Chlorine (CC) though soon after addition or at very high levels it can show up as Free Chlorine (FC) as well. You didn't say whether the chlorine level was FC or Total Chlorine (FC+CC). So perhaps the MPS has built up and your pool is quite clean with little organics to oxidize. Your Cyanuric Acid (CYA) level in the pool may be very high from continued use of Trichlor since for every 10 ppm FC added by Trichlor, it increases CYA by 6 ppm. High CYA levels can significantly slow down breakdown of chlorine from sunlight.

So between the remaining residual tabs in the chlorinator and the weekly MPS, you might have been holding oxidizer levels which is probably what is getting measured. Even so, this does seem strange.

[RMS]

I have noticed the chlorine level has been staying high in the pool despite not shocking or adding tabs to the chlorinator in a couple weeks. I have been waiting for it to come down, but it just is sitting between 8-10ppm. I also use nature 2, so I usually keep it much lower. The pool is clear, filters 8 hours a day, and is used at a moderate level. I confirmed the reading with test strips and by taking a sample to the pool store.

Is there a reason why a chlorine level would stay high for a long time like that?

thanks,

Ray

I agree with chem geek, but lay off the MPS and try using Calcium Hypo. Keep the cover off, and if that doesn't work, you may want to add Thiosuplphate to get the chlorine level down.

http://www.clean-pool-and-spa.com/swimming...l-chlorine.html