Gallons of muriatic, days of aeration...

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Originally Posted by waterbear

that's why I said to shoot for 6.8 by adding acid in small amounts and testing until you got there.;)

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Regardless of how small of an amount you add, when you are at the bottom of the scale, you can be past 6.8 and not know it, hence my caution.

Michael

I agree with Carl and Michael. Stop at 7.0. If your kit says 6.8, it could actually be lower than that.

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Originally Posted by Sigrid

Thanks all, here's the latest:

I put in a gallon of muriatic, let it run for 2 hours, got the pH to the light end of 7.2 (using Taylor kit). Just added in 1/3 gallon of muriatic to get it to drop down to the 6.8 range. BUT, before I added additional acid, I measured the alk and it said it was down to 140. Yay, Progress!! The thing is, I had a 130 on Friday morning, and then by Friday evening, it was back to 190, so I don't trust these low numbers that I get. Think I might have some errors in my methodology...

Wehn you lower the pH you shift the buffer system to more carbonic acid (carbon dioxide gas dissoved in water) so when you test TA it will give a lower reading. As the pH rises back up the buffer shifts to more carbonates/bicarbonates so when you test the TA it will test higher since the test will tell you how much alkaline carbonate ions are in the water. This is normal. The idea is to 'gas off' as much of the carbon dioxide gas that is formed by the lowered pH so that when the pH rises less of the alkaline carbonates are formed and your TA is lower. The process CAN take a while.

I appreciate the warning on not going too low on pH--my kit only goes down to 6.8. I'm going to *assume* that I'm there right now and just aerate like crazy tonight so I don't damage anything.

This is why I cautioned to make SMALL additions of acid and test pH once the pH starts moving. It is very easy to overshoot! With a plaster pool it is ok to go to as low as 6.6 according to Ben's sticky on the subject as long as you have an accurate way to test for pH that low (such as a pH meter or the correct indicator solution and comparator for that pH range)
Thanks Everyone for all the helpful info! I'll post again tomorrow w/ the new numbers.

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Hope this is helpful!

Good morning!

After dropping pH to something less than 7.2 last night and aerating overnight, I tested this morning at 7.5 pH and Alk at 130! That looks like progress and I'm delighted.

Waterbear, if I understand correctly, I can actually trust this alk number because the pH already went up, right?

I'm hoping that's the case. I just put in another 1.5 gallons of muriatic and will be aerating all day. Targeting alk in the 80-90 range (high alk fill water, heater).

Everyone, thank you so much for all the help and sharing your insights with me!

--Sigrid

Do I circulate water (along with aeration) after applying Muriatic Acid or do I pour it in the deep end and let it sit idle for 6-12 hours as others say? I'm confused because they are totally contradicting directives. Thanks

Circulate immediately. The so-called "acid column" method is pure hogwash and will damage your pool.

Michael

I agree with mwsmith2....the 'acid column' is supposed to cause carbon dioxide to gas off much like pouring acid on baking soda causes it to fizz. I have even read descriptions of it that says you might see bubbles of CO2 form and rise to the surface but that just doesn't really happen. The problem with that is carbon dioxide is very soluble in water and unless you airate the water to drive it off it tends to stay in solution. Carbon dioxide in water forms carbonic acid (think club soda....exactly the same thing). To drive the CO2 off you shake the bottle of club soda (or airate your pool!)
hope this helps.

Very nice analogy, thanks!