Gallons of muriatic, days of aeration...

[Sigrid]

Hi All. Great forum. I dismissed my pool service towards the end of April and made the move to bleach. Gotta say my water looks better than it has in years.

I've got an alkalinity issue and am hoping to get some ideas or insight as to why my alkalinity won't go down.

The pool that came with the house is an inground plaster pool. There is 1 main drain, 1 skimmer and 3 returns. I currently have one return plugged up to get higher pressure at the other two for fountains. One fountain is designed for pools and shoots a cascade of water 10' in the air; the other "fountain" is a piece of pvc tubing that shoots water in about a 4' arc. I've got lots of bubbles and the filter is running 24/7.

I started aerating to lower Alk about 3 weeks ago. The starting number from the pool store on 4/23 was 210. My own alk test this morning was 180.

My new routine is to test the pH/alk first thing in the morning. It would make my day to see a real drop in the number... Check the pH, which is invariably at 7.4, pour in a gallon of muriatic to get pH back down to 7.2 and continue aerating, hoping for a better alk number in the evening.

My questions to the forum are these: Is it normal for it to take this long for such a modest drop in alkalinity considering that I'm aerating 24/7 and keeping the pH low? And is it normal to pour in a gallon of muriatic each time I want to lower the pH from 7.4 to 7.2? I added 4 gallons of muriatic to my pool this weekend alone.

Pool is 35K gallons
FC: 6
TC: 6
pH: 7.2
TA: 180
CYA: 48 or so
Calcium: 500

Thanks in advance for any insights you can give me!

[waste]

segrid, Welcome to the forum!
It will take some time for the alk to drop ( I think your drop to date is good, given your ~large pool). I know you want it to be 'right' right now, but patience and perserverance will do you better than any 'quick - fix'. As long as you don't have an immediate problem concerning the alk level, doing the lowering slowly will prevent future problems.

Congratulations! You have decided to 'take control' of your pool, rather than just getting 'someone else' to fix the issue! You have done 2 good things; i.e. taking your pool into your own hands and comming here to learn 'how to do it properly'. Should you ever need help with anything, feel free to ask me or post (the folks here are the GREATEST!!).

Once you've taken care of this 'temporary problem', if you follow the advice here you shouldn't have any more problems !! :)

[Sigrid]

Thanks for the info. It's rather disappointing to think that I'll need to aerate for 8 more weeks before I get alk down to where I want it. So be it. I've got patience, just getting a little tired of the fountains!

Any thoughts on the amount of acid? Per THE calculator, I recall something like 27 oz of muriatic to drop pH by .2, and I'm putting in a gallon to get the same effect.

Again, thanks for your help!

EDIT by Watermom - Sigrid, don't worry about the accidental double-post. I took care of it for you.

[waterbear]

My new routine is to test the pH/alk first thing in the morning. It would make my day to see a real drop in the number... Check the pH, which is invariably at 7.4, pour in a gallon of muriatic to get pH back down to 7.2 and continue aerating, hoping for a better alk number in the evening.

My questions to the forum are these: Is it normal for it to take this long for such a modest drop in alkalinity considering that I'm aerating 24/7 and keeping the pH low? And is it normal to pour in a gallon of muriatic each time I want to lower the pH from 7.4 to 7.2? I added 4 gallons of muriatic to my pool this weekend alone.

Pool is 35K gallons
FC: 6
TC: 6
pH: 7.2
TA: 180
CYA: 48 or so
Calcium: 500

Thanks in advance for any insights you can give me!
The process might go a little faster if you get your pH down to about 6.8 before you start airating. There will be more of the alkalinity as carbonic acid instead of bicarbonte and that would make your airation more effective at driving more off in less time. Keep the pH down while you airate and monitor the ALK until you hit your target.

As far as how much acid you need...remember, ALK is actually a buffer system that tries to resist changes in pH. You might need a lot of acid (especially given the size of your pool) to get it to start moving but once it does it will move fast! This is why it is best to add the acid in small amounts and test the pH. If it isn't below 7 then add more acid. Don't start airating until you get the pH below 7 and keep it there while you airate until your Alk is at your target. This should speed the process up a bit for you.

Hope this helpt!

[CarlD]

Try getting your pH down to 7.0 in the morning, rather than 7.2. Perhaps it will go a little quicker.

[Sigrid]

Thank you!! I love this forum. I will get the pH a little closer to 6.8 before aerating.

One more question: What, besides fill water (my fill water alk is 170) causes the alk to increase? Would all those decomposing leaves that spent winter at the bottom of my pool be a culprit?

Thank you so much. I can't tell you how much I value the information I get here.

Watermom, thanks for removing my duplicate posts.

[mwsmith2]

It's true that 6.8 will burn off the alk faster, but since that is at the bottom end of the range of a phenol test, it's a dangerous place to be, mainly because you can be below 6.8 and not know it. The only time I'd head for 6.8 would be if I had a pH probe (and I do :P) 7.0 is close enough! :D

Michael

[CarlD]

I have to agree with Michael--try to hit 7.0. But you DID say you have a concrete pool didn't you? You are a lot safer if you go too low with pH than a vinyl pool owner.

[waterbear]

I have to agree with Michael--try to hit 7.0. But you DID say you have a concrete pool didn't you? You are a lot safer if you go too low with pH than a vinyl pool owner.
that's why I said to shoot for 6.8 by adding acid in small amounts and testing until you got there.;)

[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...

New muriatic has been circulating for a couple of hours, and then I'm going to fire up the fountains over night to see (hopefully) a lower alk # in the AM.

Michael, I apologize for not giving you proper credit for your calculator in my earlier post. It is a godsend. Thank you.

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.

Thanks Everyone for all the helpful info! I'll post again tomorrow w/ the new numbers.

[mwsmith2]

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

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

[Watermom]

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

[waterbear]

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.

Hope this is helpful!

[Sigrid]

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

[kennysacht]

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

[mwsmith2]

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

Michael

[waterbear]

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.

[waste]

Very nice analogy, thanks!