Trouble with alklinity

avspin · Jun 3, 2015

Getting frustrated. Background 20,000 gallon salt water fiberglass pool covered. I've got it pretty good, ph 7.5, hardness 300, cyn 35 BUT Alkalinity 150. So I tried to lower alkalinity by adding muriatic acid. Then upping the ph. I was using sodium carbonate but was told by local store it would also raise alkilinty at the same rate so switched to soda ash. More muriatic acid and alkalinity got down to 100 and ph 6.8. So in with soda ash.
Now ph back to 7.4 but alkalinity back up to about 180.
I'm at a loss as to how to lower alkalinity to get it in line with ph.
Any advise?
Thanks

Azgirl71 · Jun 3, 2015

Welcome to TFP! It is actually a process. You cannot just add MA once. You have to do it over several weeks. Here is a link that shows the process I have been going through. You can see it has been a long process.

Results after SLAM

Pool School - Lower Total Alkalinity

bdavis466 · Jun 3, 2015

The only way to raise the pH without raising the alkalinity with it is trough aeration.

Lower the pH to 7-7.2 and aerate to 7.4-7.5 and repeat...

avspin · Jun 3, 2015

So if I leave the cover open and run the 6 fountains (5' arcs plumbed from the return lines located on the deck) for a few hours each day will raise the ph. Then lower both ph and alkalinity with acid and repeat until my desired level.
How long should i let the fountains run each day?

bdavis466 · Jun 4, 2015

That is correct.

It all depends on how quickly you are trying to lower your alkalinity. The more you run them, the more pH rise you will get. Your pH will rise much quicker at a pH of 7 as opposed to a pH of 7.6

avspin · Jun 4, 2015

Thanks I will start tomorrow and keep you appraised of my progress.
Steve

Scuba_Steve · Jun 4, 2015

It is a slow process though so just be warned. Do not expect results in a few days. It takes me roughly 3 days to go from 7.0 to 7.3 and I seem to be losing about 4-6 ppm of TA each time I relower.

avspin · Jun 9, 2015

Update after a week, I've been aerating the surface with my fountains for about 8 hours a day. When the ph gets to about 7.6 I add MA and it drops to about 7.0. I've done this 3 times over the last week. No other water or chemicals have been added. Meanwhile the TA went to 210, I attribute this to the water settling after adding the soda ash last week. today the TA has slowly dropped to 180.
Is this the typical time frame I should expect?
Thanks,
Steve

Azgirl71 · Jun 9, 2015

I takes a few weeks sometimes longer.