Heater causing increase in pH

[Deb Driesen]

With everything else in balance I just don't see why simply running my pool water through the Coates 11kw heater increases the pH so dramatically. To investigate the problem further we tested our tap water which is filtered well water. The pH is fine in cold tap water but goes up to 8 in hot tap water, which goes through a propane tankless water heater. So...Why?
Why does simply heating water raise the pH? Conversely, letting heated tap water cool down maintains the high pH. I am annoyed that I constantly have to add muriatic acid but beyond that I really want to understand this.
Also I want to edit my profile to delete the swcg which removed because it was increasing the pH so much. The only edit I can do in my profile is in the banner. Any tips?

 

[mknauss]

Warm water cannot retain as much CO2, so when you take cold water and warm it, it releases CO2 which drives up the pH. Once your TA is at a lower level, this effect will stop.
SWCG does not raise the pH in pool water.