Pentair 320 Chlorinator


New member
Apr 25, 2019
Rio Rancho, NM
Hello! I recently went to a local pool store with a water sample and the technician advised me to stop using my chlorinator and chlorine tablets and told me to start using non-cya increasing tablets. So I tried to turn off the chlorinator and the knob won't go all the way to the off position. It gets close, but doesn't actually point to off. Is this okay and does this suffice for my chlorinator being 'off'? Also, even when it's pointed to the off position the chlorinator still filled with water. I had the cap off and turned my pool pump on so I could see what happened in the chlorinator even with it in off position and it still filled up. Is that normal and okay? One of the tubes to the chlorinator also sprung a leak because the tubing is very old and dried out. Now I'm trying to seal it because water is still flowing through there even with it off and I'm leaking water. Any advice would be so appreciated! I just bought this home and I'm a new pool owner too. The pool already had to be drained and acid washed and filled back up and the company that came out put the chlorine tablets in the chlorinator and said everything was fine. Less than two weeks later I go to the pool store and the worker is telling me to shut off my chlorinator immediately and use the other tabs. I just don't want to have a mess of a pool! Thanks!


Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Rachel, welcome to TFP! :wave: I have a Waterway version, not the Pentair 320, but I suspect the knob may just be slightly off on its indications. But here's the more important thing for you to take from this ........ non-CYA tablets means Cal-Hypo (calcium). You do not need that either. I suspect your local water is quite hard right? So your CH levels will jump quickly each season with evaporation refills and such, so that thing you ned to do is add more calcium. Those inline chlorinators are convenient if you are away from home for a couple days or so, but we never recommend them for long-term use. They either increase CYA (as you leanred) or CH if you use cal-hypo.

Instead, rely on liquid pool chlorine and/or "regular" bleach. Yep, that's it - same thing. With bleach, just make sure it's not Clorox, or anything with fabric softeners, splashless, or scented. Just the plain stuff. Yes, you need to add x-amount each day to maintain the proper FC level, but that is generally very easy and can be done at the same time you go out to check the skimmer and stuff. Always add chlorine/bleach slowly near a return jet. Use our PoolMath tool to determine how much bleach to add.

I would also encourage you to read our ABCs of Pool Water Chemistry, FC/CYA Chart, and the other Vital Links below in my signature. Make sure to update your sig too! Proper home testing is what we base everything on here at TFP, so make sure you have a proper test kit - either a TF-100 (my favorite) or Taylor K-2006C Test Kits Compared. Stick around and let us know if you hae any questions.


Gold Supporter
May 19, 2017
Help please. I use liquid chlorine as my primary sanitizer. As I will be going on vacation this summer, I want to use the Pentair Rainbow 320 tablet chlorinator that's on the system (just while we're gone). I am doing some testing to see how long tablets last, how much chlorine they're adding, etc. I loaded the feeder with 9 tablets 6 days ago. I checked it today and was surprised to see that essentially no tablet erosion had occurred. Clearly I'm not getting the flow through the chlorinator that I should. Any ideas or troubleshooting tips would be greatly appreciated! Thanks in advance!