How much muriatic acid can I add at a time?

[crystallake]

Hello. I have a two-year old 16,000 gallon plaster pool with a dark pebble-tec finish. The pool guy has stopped coming around and I've taken over maintenance duties and balancing my chemicals the past several days. When I started, the pH levels were high so I have added two pints of acid a day the past two days and it is now down to 7.4, but the alkalinity is still high at 130 so I understand I need to get it down to 7.0 and then aerate it back up (correct?). According to PoolMath I need to add 64 oz of muriatic acid to get the pH down to 7.0. Can this be done all at once or should I continue adding a couple pints a day until I get down to 7.0? How long should I wait to test the pool after adding acid to get an accurate pH reading?

I have a SWG so chlorine levels are steady at 4.0ppm. There was no CYA in the pool so I added 3 lbs of granules yesterday and it went up to close to 40. I added another 2 lbs today. Trying to get it up to 60-70. My readings tonight right before adding the 2 lbs of CYA were:

FC - 4.0
CYA - 40
pH - 7.4
Salt - 3500
TA - 130
CH - 410

Appreciate any thoughts on getting things squared away. With all the great information on here and the amazing PoolMath app I finally feel like I can really do this. I've taken on cleaning the SWG regularly, cleaned out the cartridge filter myself last week for the first time, bought a Dolphin S200, and this pool guy is going to be a thing of the past. Cheers everyone!

 

[PoolStored]

Most here recommend managing pH and worry less about TA. TA will come down over time as your pH rises naturally, and you add Muriatic.

You can test again after an hour and it should be fairly accurate. Make sure pump is running for the hour. As always, add acid to water. You might also reduce pH is increments to ensure your calculations are correct. Adding 64 oz. when you have never made that big of a change before....just sayin'

If you are determined to get it down quickly, then here is some good reading:

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

I built this type of aerator, on a sump pump. I can reliable reduce TA by 10 every 12 hours.

 

[crystallake]

Most here recommend managing pH and worry less about TA. TA will come down over time as your pH rises naturally, and you add Muriatic.

You can test again after an hour and it should be fairly accurate. Make sure pump is running for the hour. As always, add acid to water. You might also reduce pH is increments to ensure your calculations are correct. Adding 64 oz. when you have never made that big of a change before....just sayin'

If you are determined to get it down quickly, then here is some good reading:

Lower Total Alkalinity

A lower Total Alkalinity level can help a pool owner stabalize their pH increase. We'll explain how to lower TA with a little help from muriatic acid.

www.troublefreepool.com

I built this type of aerator, on a sump pump. I can reliable reduce TA by 10 every 12 hours.



View attachment 403845

Oh man, this was so helpful to read...thank you! The only number I was having trouble with was the TA so it's good to know I don't need to worry about it too much. I figured it wouldn't be a good idea to dump a half-gallon of muriatic acid in all at once, but it was worth asking. Now I can focus on getting my CYA in check and things should be good.

Quite the aerator you built! Nice work!

 

[PoolStored]

The only thing that you will find with TA of 130 is that your pH may tend to rise more quickly. As you add MA to reduce the pH back to range, it will lower your TA. Over time as your TA comes down, your pH rise will slow.

Many on SWCG will run their TA about 60 and have much slower pH rise.

Do you add water frequently? Have you tested your fill water for TA?

 

[crystallake]

The only thing that you will find with TA of 130 is that your pH may tend to rise more quickly. As you add MA to reduce the pH back to range, it will lower your TA. Over time as your TA comes down, your pH rise will slow.

Many on SWCG will run their TA about 60 and have much slower pH rise.

Do you add water frequently? Have you tested your fill water for TA?

That is good to know. I will be keeping a close eye on pH levels from here on out and it's good to know that TA will eventually decrease. I may take a slightly aggressive approach next weekend and aerate with the spa jets for a day to give the process a bit of a boost. I am also hoping the TA reduction helps with lowering the Calcium Hardness.

I have an auto-fill valve so I do not add water at all. I should test our tap water to see if it runs high TA. Great idea.

 

[Saturn94]

An important note on Pool Math regarding pH adjustments;

“ Note: pH calculations are not exact. These numbers are only suggestive of the relative magnitude of the pH change you can expect. Small changes, +-0.4, with pH between 7.2-7.8, TA around 80-120, and Borate near zero will be approximately correct. The further you go from those ranges the less these pH changes will correspond to reality.”

 

[crystallake]

An important note on Pool Math regarding pH adjustments;

“ Note: pH calculations are not exact. These numbers are only suggestive of the relative magnitude of the pH change you can expect. Small changes, +-0.4, with pH between 7.2-7.8, TA around 80-120, and Borate near zero will be approximately correct. The further you go from those ranges the less these pH changes will correspond to reality.”

Yes, very important to note. Key takeaway is to move in baby steps. There's no real rush. Thanks!

 

[PoolStored]

I have an auto-fill valve so I do not add water at all. I should test our tap water to see if it runs high TA. Great idea.

Yep! If your auto-fill has high TA, then you will battle with your TA and pH rise. At that point, it might make sense to see if MA and your spa jets help, or build an aerator.

 

[crystallake]

Yep! If your auto-fill has high TA, then you will battle with your TA and pH rise. At that point, it might make sense to see if MA and your spa jets help, or build an aerator.

Just what I need…another project!

 

[MITBeta]

I have a SWG so chlorine levels are steady at 4.0ppm. There was no CYA in the pool so I added 3 lbs of granules yesterday and it went up to close to 40. I added another 2 lbs today. Trying to get it up to 60-70. My readings tonight right before adding the 2 lbs of CYA were:

Did you raise your chlorine level to match the new CYA level? FC/CYA Levels

 

[crystallake]

Did you raise your chlorine level to match the new CYA level? FC/CYA Levels

At 4.5 today and a steady climb to stabilize at 5.0 hopefully tomorrow. Still tinkering with output percentages at the moment. Aiming for a 5.0/70 ratio

 

[PoolStored]

At 4.5 today and a steady climb to stabilize at 5.0 hopefully tomorrow. Still tinkering with output percentages at the moment. Aiming for a 5.0/70 ratio

SWCG is intended to maintain FC, not so good at raising FC. Go ahead and use LC to get to your target, then tinker with output percentage.

You want to target the top of the range, 6-7. That will allow for some high FC demand days.

Go ahead and get it to 7 with LC, then tinker away. You will find you likely need to increase the output as you go into summer, then it will fall in the fall.

 

[AK-]

I am also hoping the TA reduction helps with lowering the Calcium Hardness.

Reducing TA will do nothing to CH.

CH is one of those things that only decreases by dilution (replacing water).

 

[crystallake]

SWCG is intended to maintain FC, not so good at raising FC. Go ahead and use LC to get to your target, then tinker with output percentage.

You want to target the top of the range, 6-7. That will allow for some high FC demand days.

Go ahead and get it to 7 with LC, then tinker away. You will find you likely need to increase the output as you go into summer, then it will fall in the fall.

Interesting. I wasn't aware of that and thought I had read somewhere that you need to adjust percentages until you get the FC level you like. I'll pick up some LC tomorrow.

As an aside, I put in a quart of acid this morning before work. Came home to a pH of 7.4 and TA of 120 so I put in another pint of acid tonight. My pH really seems to hold. I will play the tortoise and take the slow race to the finish.

 

[crystallake]

Reducing TA will do nothing to CH.

CH is one of those things that only decreases by dilution (replacing water).

Thanks. I guess I have to live with hard water because I'm stuck at low 400s.

 

[PoolStored]

I had read somewhere that you need to adjust percentages until you get the FC level you like

Get it to your FC level, then adjust % and runtime to find what will maintain FC.

Use LC to get to your desired level, 6-7. Then tinker with the %output to maintain it at 6-7 daily. Are you running your pump 24/7? The Jandy PLC700 is a 12K gallon cell. We recommend using a 2x pool volume cell. It is likely your cell is severely under-sized.

I will play the tortoise and take the slow race to the finish.

You will get it. The pool is a dance. #always learning.

 

[crystallake]

Use LC to get to your desired level, 6-7. Then tinker with the %output to maintain it at 6-7 daily. Are you running your pump 24/7? The Jandy PLC700 is a 12K gallon cell. We recommend using a 2x pool volume cell. It is likely your cell is severely under-sized.

I used to run the pump an average of 9 hours a day from April through October and six hours a day from October to April. I changed it today to run 24/7 at 1100 RPM for 18 hours and 1500 RPM for 6 hours

I noticed the SWG was undersized as well about six months after its installation. I was pretty annoyed at my pool guy for it, but at this point I am going to ride this one out until it's time to replace with a PLC 1400. It was installed April 2021 and has been doing its job.