Ph rise and chlorine rise after new heater


Gold Supporter
LifeTime Supporter
Nov 29, 2015
Carrollton tx
I replaced a low no heater w a atmospheric raypak heater

After 3 months of very stable pH with almost no acid needed

Now we have covered the pool w floating cover and heated pool from 68-72 to 85

The swg has been running at 60% for months and averages 4-5 ppm.

Tonight the cl ppm was 20 and the pH was 7.8 or higher ....

Could cold weather and a new heater cause pH rise ?

I'm confused

I've turned off the swg after my SO has. Reaction from hot tub w that cl level ...


TFP Expert
In The Industry
Jul 6, 2011
The heater will not cause any changes in any of your pool water chemistry. Cold weather can affect your water along with putting a cover on it. Usually during the cooler months you dial back your chlorine as it won't burn off like in the warmer months. Same goes for your PH. A cover will have alot to do with it.


TFP Expert
Mar 2, 2011
The pH is not going to be accurate if the fc is over 10. You need to let the fc drop below 10 to get an accurate fc reading.

pH also rises if the SWG causes an increase in fc. (SWGs are pH neutral if the fc remains constant. The pH rises with fc rise and falls with fc drop).

The cover reduces fc loss, so your percentage needs to be dialed way back.

A cover also reduces pH rise due to carbon dioxide offgassing. So, in many cases, the pH will rise less with a cover.

What are all of your chemistry readings?