Trying to lower alkalinity

[cheri]

Hello,

I have the following readings on my cement pool (which I guess would be called "plaster"):

FC - 7 ppm (and I did the overnight test and it lost no chlorine)
CC - zero
CYA - 45
TA - 200 (same as yesterday, after adding 40 ounces of muriatic acid @ 14.5%
PH - 7.2 (was 8.2 yesterday)

I'm trying to get the TA down to 90. I think I need add 55 ounces of borax first to get the PH up to 7.8 or higher. Then, I should add another 40 ounces of muriatic acid. Could someone tell me if this sounds like a wise plan?

Thanks!

 

[Richard320]

Don't bother. If TA is really that high, your pH will spring back in a hurry.

And I wouldn't even bother with TA by itself. Just by maintaining pH with acid you will work the TA down.

 

[cheri]

Thanks Richard. I have some stains on the walls of my pool I was trying to address and that's why I did all of the recommended tests. Also, I was bad and hadn't cleaned out my filters in a while. I finally did a thorough scrubbing of them and so I'm trying to get all of my pool levels to a good level.

So, when you say you wouldn't bother with the TA, do you mean you wouldn't add more muriatic acid to try to lower it further? I should just focus on keeping the PH level at 7.2. 200 seems pretty high.

Would you recommend I slam the pool to address the stains?

 

[cheri]

Here is a picture of the situation I'm trying to address.

Thanks anyone and everyone.

 

[Flying Tivo]

There is a process for lowering TA. It calls for lowering your ph to 7 with MA and then aerate. You will need to build a pvc pipe to connect to the return and make a fountain so aeration can take place. Aeration will bring back up your PH, when it comes up to 7.5, lower it again to 7 and cycle again until TA comes down.

 

[aussieta]

encourage plenty of splashing and your ph will rise in no time
then adjust ph back down to 7.2
repeat as required
each time you lower ph you also lower ta
ta is usually not an urgent adjustment, if it takes the whole season so be it
might be an idea to test your fill water ta, ph, hardness

 

[cheri]

Thanks Felipe. I just stuck a piece of irrigation hose in there and it is creating a line of water. I wouldn't call it a "fountain" but I could attach a sprinkler if that would make it better. Couldn't I also just turn on my jets to the hot tub to aerate that part?

So, the idea is to just keep that fountain going until the TA number goes down?

 

[cheri]

encourage plenty of splashing and your ph will rise in no time
then adjust ph back down to 7.2
repeat as required
each time you lower ph you also lower ta
ta is usually not an urgent adjustment, if it takes the whole season so be it
might be an idea to test your fill water ta, ph, hardness

Thanks aussieta.

And for the stains? Other than continuing to scrub them, do you have any advice for that?

I can get in there and splash around. It's close to 100 degrees here in Vegas.

 

[Flying Tivo]

Yes the spa jets are the best source of aeration but on your signature you dont mention if the spa and the AGP are connected?

 

[cheri]

Yes the spa jets are the best source of aeration but on your signature you don't mention if the spa and the AGP are connected?

Oh, my bad. I moved to a new place with a hot tub and didn't update my profile. I'll turn the jets on if that will help the situation. My little hose attachment is working out well too as it just happened to land in a way where it is creating a fountain-like scenario.

Thanks so much! I guess I won't add the borax after all. Now, I just need to figure out how to get rid of these stains.

 

[Flying Tivo]

Adding MA then Borax is like playing Yo-Yo!

 

[cheri]

Adding MA then Borax is like playing Yo-Yo!

That was what I thought. But I read somewhere that you had to raise the PH to a higher number and then add more muriatic acid to lower the alkalinity. It didn't sit with me right, so I decided to come to this forum. Everyone is always so helpful here. I'm going to let my home-made fountain and spa jets run for the next few hours and then add the muriatic acid when the sun goes down.

Now, if anyone has advice for dealing with the stains, I'd appreciate it. My gut says to SLAM the pool, but my gut is not always right.

 

[Richard320]

Those stains look like algae, possibly embedded in calcium scale.

As long as you're getting in, bring along a stainless steel pool brush and have at it. See if you can loosen things up. Feel those stains. See if they're rougher than the surrounding plaster. That'll tell you if it's scale.
And is there a reason you didn;t test Calcium Hardness? In Las Vegas, that's kinda critical. You people have hard water and a lot of evaporation which makes it worse. Scale is a serious threat.

 

[cheri]

Those stains look like algae, possibly embedded in calcium scale.

As long as you're getting in, bring along a stainless steel pool brush and have at it. See if you can loosen things up. Feel those stains. See if they're rougher than the surrounding plaster. That'll tell you if it's scale.
And is there a reason you didn;t test Calcium Hardness? In Las Vegas, that's kinda critical. You people have hard water and a lot of evaporation which makes it worse. Scale is a serious threat.

That's the only thing I didn't test. It is 850. Yikes! Do I have to drain part of the pool? I don't see anything I can add in the pool math page.

 

[Richard320]

Reverse osmosis is one option, if anyone in Las Vegas does it. The other is drain and refill. But I;d hold off on either until you've worked out what these stains are and if they'll scrub off.

If they are Calcium scale colored with algae or rust, then a sandblasting or acid wash is called for, and the guys that do that will have to drain it then.

 

[cheri]

Reverse osmosis is one option, if anyone in Las Vegas does it. The other is drain and refill. But I;d hold off on either until you've worked out what these stains are and if they'll scrub off.

If they are Calcium scale colored with algae or rust, then a sandblasting or acid wash is called for, and the guys that do that will have to drain it then.

I can't feel anything and I wouldn't say it feels "scaly." Short of the acid wash, should I do anything to address the calcium levels? I see there are products that say they address it.

I'd like to try to address the issue myself first before I go to that extreme. Also, I will scrub it for the next week and see what happens.

Thanks for your help.

 

[Richard320]

If it's just stained and not rough, see if it's metals. Get a Vitamin C tablet -- nothing special, cheap as you can find. You only need one or two so ask around before you go buy a bottle -- and rub it on a stain like chalk. Wait five minutes and brush it away. If that's metal staining, it;'ll be clean where the tablet was rubbed.

 

[jseyfert3]

That was what I thought. But I read somewhere that you had to raise the PH to a higher number and then add more muriatic acid to lower the alkalinity. It didn't sit with me right, so I decided to come to this forum. Everyone is always so helpful here. I'm going to let my home-made fountain and spa jets run for the next few hours and then add the muriatic acid when the sun goes down.

Now, if anyone has advice for dealing with the stains, I'd appreciate it. My gut says to SLAM the pool, but my gut is not always right.

It's true, with one big but. The but is that you cannot add anything to raise the pH! The only way to lower TA is by adding acid. To raise the pH without adding anything you have to aerate.

If I recall correctly, and trying to simplify, the TA makes the water over-carbonated, in the form of carbonic acid, which lowers the pH. This "holds" the pH low. When you aerate, you drive off carbon dioxide, removing the carbonic acid, and the pH climbs due to the lack of this acid. Adding MA will drop the pH, and the TA will change into carbonic acid (lowering the TA), so if you aerate again your pH will climb. This will happen until your TA reaches a point where further aeration will not cause pH climb. Note this probably isn't completely scientifically accurate, it's been a year or more since I read chemgeek's post on this.

For a normal pool with little aeration, this process is slow, and so acid can be added every few days/once a week or so. Hence why TA is normally ignored except as part of the CSI calculation for pools, and acid is only added to control pH rise. On the other hand, a standalone hot tub has so much aeration the pH climbs to something like 8.5 within 15-30 minutes of aeration. This is why in the spa section the instructions are to due the aeration/acid method on a new fill to knock the TA down to roughly 50 ppm, at which point further aeration has little to no ability to raise the pH.

The real question is do you need to lower your TA? Unless needed to keep the CSI in check, or because of unusual amounts of aeration such as a water feature causing the pH to climb to fast to control with acid, the TA is typically not adjusted except as a byproduct of using acid to lower the pH.

 

[cheri]

If it's just stained and not rough, see if it's metals. Get a Vitamin C tablet -- nothing special, cheap as you can find. You only need one or two so ask around before you go buy a bottle -- and rub it on a stain like chalk. Wait five minutes and brush it away. If that's metal staining, it;'ll be clean where the tablet was rubbed.

Thanks again Richard. You are so nice! I'm sure I have some vitamin c around the house somewhere. I'll try it out.

 

[cheri]

It's true, with one big but. The but is that you cannot add anything to raise the pH! The only way to lower TA is by adding acid. To raise the pH without adding anything you have to aerate.

If I recall correctly, and trying to simplify, the TA makes the water over-carbonated, in the form of carbonic acid, which lowers the pH. This "holds" the pH low. When you aerate, you drive off carbon dioxide, removing the carbonic acid, and the pH climbs due to the lack of this acid. Adding MA will drop the pH, and the TA will change into carbonic acid (lowering the TA), so if you aerate again your pH will climb. This will happen until your TA reaches a point where further aeration will not cause pH climb. Note this probably isn't completely scientifically accurate, it's been a year or more since I read chemgeek's post on this.

For a normal pool with little aeration, this process is slow, and so acid can be added every few days/once a week or so. Hence why TA is normally ignored except as part of the CSI calculation for pools, and acid is only added to control pH rise. On the other hand, a standalone hot tub has so much aeration the pH climbs to something like 8.5 within 15-30 minutes of aeration. This is why in the spa section the instructions are to due the aeration/acid method on a new fill to knock the TA down to roughly 50 ppm, at which point further aeration has little to no ability to raise the pH.

The real question is do you need to lower your TA? Unless needed to keep the CSI in check, or because of unusual amounts of aeration such as a water feature causing the pH to climb to fast to control with acid, the TA is typically not adjusted except as a byproduct of using acid to lower the pH.

Thanks for the explanation, jseyfert3. My PH was up to 8 again today, probably as a result of all of the aeration I did yesterday. I let the jets run in the hot tub for a while yesterday. Today, I'll just use my homemade fountain. I have some advice for thinking through how to address the stains as well.

Just curious, since you seem to have thought through all of the chemicals a lot. I'll stop worrying about the TA. But it just feels like I need to do something when my TA was super high and so was the calcium hardness (800). Would you not worry about that as well? I saw you mentioned the CSI calculation, which I read about yesterday. It felt like too much work at the time. I thought someone would have a formula and I'd just enter my numbers. But I never saw a formula.

Any advice is appreciated.