Cold Water and Tabs/Powdered Chlorine

  • Last Post 25 April 2020
Jlk21277 posted this 25 April 2020

The "stay-at-home" orders make me start looking for things to do in northern Ohio so I opened my inground pool. I cannot get the chlorine level above 0-1 ppm.  I have a 17,500 gallon pool. I added 2 lbs of powdered shock to the pool. Most of it appeared to sink to the bottom. I ran my Pool Vac and it looked like a lot of the chlorine was vacuumed up and forced through my filter. (Lots of white clouds in the return ports.) 12 hours later - still no chlorine level. 

I also filled my Rainbow 300 automatic chlorinator with 3" tabs and turned the valve to #6 (fully on). 12 hours later, still no noticable erosion of the tablets. 

The water temp is 48. Is this too low to dissolve the powdered chlorine products?

Would it help if I predissolved the powdered shock in hot water? I am concerned that as soon as I add it to the pool the chlorine will precipitate out. 



InyoRob posted this 25 April 2020

The cold water, anything below 65°, has an impact on the ability of the chemicals to dissolve properly. I would recommend using liquid chlorine if you have to shock in lower temperatures. 

You can dissolve granular shock in warm water. Perhaps it will work if you completely dissolve it before adding it to the pool.

Cold water can impact the ability to get a proper chemical reading. I wouldn't be concerned too much because algae will not grow when the temperatures are that low. Keep an eye on the chlorine as the temperatures warm up. If you are shocking the pool but not getting a free chlorine level, your stabilizer (CYA) level may be too high. In that case, you would partially drain the pool and refill it.