Ph suddenly stabilizes

[dykes26]

We have had our pool for about a year and have had to add about a cup and of half to two cups twice a a week. All of the sudden the Ph has stabilized and is resting at about 7.4-7.5 no spike in a month. Is that normal?

 

[chem geek]

Depending on what has changed, that can happen. For example, if you had lots of aeration before, say from running waterfalls or spillovers, and you turned that off, then the rate of carbon dioxide outgassing would slow down and hence the rate of rise in pH would slow down. As another example, if you were running your saltwater chlorine generator (SWG) with a high on-time before and now turned it down or off, then that would reduce the rate of pH rise from that source, be it undissolved chlorine gas outgassing or aeration from hydrogen gas bubbles. Another example is if you cover the pool which significantly cuts down carbon dioxide outgassing. These are three examples of change that can cause a rapid difference in pH stability.

A change that is slower over time is having your plaster cure. Initially, such curing is rapid and the rate of pH rise is high and lots of acid is needed, but this slows down over time. This process probably slows down with colder temperature so if the water is getting colder then that could affect not only the curing rate, but also the outgassing rates.

 

[Brentr]

I noticed the same thing too, but I thought it was because of the very cold temps we have had in the last month.