How to "neutralize the acid" ?

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gkran

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Feb 20, 2008
29
We have an IG gunite ~ 12k gal pool. Resurfaced last year, had some splotching and calcium build up, so we just had it acid washed. We are refilling the pool now. The pool person set to add 7 gal of muriatic acid, let it sit for 24 hours, neutralize the acid, and then start the equipment and pool. This is to get rid of the calcium build up.

I wanted some advice on neutralizing the acid. Do I just use baking soda until my pH is in range? Or is it more complicated (do I need to monitor alkalinity as I do this)?
 
Welcome to TFP!

Baking soda and borax and soda ash will all neutralize the acid. Of the three borax will raise the TA the least and baking soda will raise the TA the most. I suggest using borax till you get the PH somewhere plausible and then adjust the TA if needed with baking soda.
 
Actually, if the pool was just acid washed it might be better to do a base demand test with a testkit that includes one and use soda ash to get the pH up. This might get your TA a bit too high but will be more effective. On a weight for weight basis you will need about half as much soda ash as borax for the same pH rise. Usually this should be part of the acid wash procedure! BTW, the acid wash should have gotten rid of the calcium! By adding the acid to your pool you are doing another acid wash yourself! Doesn't sound quite right to me!
 
By adding the acid to your pool you are doing another acid wash yourself! Doesn't sound quite right to me!
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I'm certainly no expert on the procedure but I'm with Evan....sounds like you're doing a double "wash". Maybe he has found this technique to be very effective. I'd be interested in learning more if he'll share his philosophy.
 
This may be part of the acid wash procedure. The pool company did the acid wash because of our complaints about mottling. This may be a way of having us bear some of the cost, which is fine. I would rather do the chemicals myself, but not scrubbing the surface.

Traditionally, TA has not been a problem with this pool. We have a waterfall and cascades from the jacuzzi, which I believe helps. It has taken a lot of acid during the first year after the resurface.

Any ballpark idea how much borax or soda ash I will need?

I assume that I can start adding salt once the pH and TA is stable?
 
Thanks. I just switched to this pool site and am still finding my way around.

Is there a list in the forums on the best way to start up a re-filled pool?
I planned on getting pH and TA in range, adding CYA and chlorine, and then start adding salt.
 
My Pool Calculator is not accurate for large PH changes.

It is a little over 2 lbs of soda ash for each quart of acid, or just over 4 lbs of borax per quart of acid. Keep in mind that some of the acid will have been neutralized by dissolving plaster and calcium scale, so you can't know exactly how much you will really need. You want to go in stages, adding perhaps half the total at first and then smaller amounts each time as you approach your goal.

For starting up a pool the most important thing to keep in mind is that you don't want to be adding calcium on the same day that you are raising the PH or TA. Salt can be done any time. Chlorine should start right at the beginning and get added as needed (often daily). If the TA is very low (<30) then it is best to raise the TA a little before adjusting PH. Also keep in mind that raising PH raises TA a little, lowering PH lowers TA a little, and raising TA raises PH a little.

If you measure your fill water in advance you can get an idea of which chemicals you are likely to need to have on hand.
 
This is one of those rare situation where the acid and base demand tests are needed. If you have access to a Taylor K-2005 or K-2006 you can do a base demand test.
 
OK.

I added A&H washing soda to the jacuzzi to see how things go. I overshot the pH a bit, but won't be a problem once it circulates with the pool. But the water in the jacuzzi is milky/cloudy. Is this normal and will it clear up? Is this something that will need filtering? Or did I so something wrong?
 

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As you raise the PH the calcium that the acid wash took off the pool walls and put into solution can precipitate out again. Sometimes this happens as tiny particles that turn the water milky and can be filtered out and sometimes it deposits as scale back onto the pool walls. This is especially likely if you overshoot the PH.

If you go slowly and don't overshoot the PH you will probably be alright, but it depends on just how high your CH level has gotten. Now would be a good time to do a CH test to see how high it got and how careful you need to be.
 
Thanks for the quick reply.

My fill water CH is 190. I just measured the pool CH at ~ 250. (I am using Ben's kit, and CH seems to be one of the trickier tests for me to run consistently).


Before we resurfaced last year, the pool had very high CH, ~500

So should I get the pH in a reasonable range and start filtering? Or is this a case where I may need to pump out water and refill?
 
Pool CH is 250; pH is low (yellow solution).

Currently:
I overshot the pH in the jacuzzi and its water is milky.
I had added several boxes to the pool. The pH is very low, but there is a cloud from where I added the Washing Soda.

For the jacuzzi, is it best to drain and refill? Or do I just filter it?
Can I start the pool equipment with the pH low?

Am I adding the Washing soda incorrectly? I sprinkle the box over the surface and brush where it settles to the bottom. There will be an area of water where the WS is concentrated for a moment. Is this enough to precipitate out the CA.

Any help is appreciated.
 
Alright that is good. THe CH level is low enough that there won't be any problems as long as the PH stays below 8 (or maybe a little higher depending on TA).

You need to get some circulation going to mix everything together! The CH level is reasonable and as long as you keep the PH below 8 everything should be fine. Adding washing soda will increase the PH above 8 right at the point where the washing soda is added, which will cause calcium to precipitate but only locally. As long as you can get some circulation happening there shouldn't be any scaling.

I suggest pre-mixing the washing soda with water in a bucket and pouring that slowly into a skimmer with the pump running. That will promote rapid mixing and will keep the PH at the equipment pad reasonably high. Any period of low PH at the equipment pad will be very short and should not cause any problems.

You want the spa water to mix with the pool water. If you have a spill over mode that will do it.
 
Thanks for your help. I usually only have to add acid, so I forgot about adding chemicals through the skimmer.

The pH is still slowly edging up to 7.5, but I have acid on hand and am monitoring it closely. I will tackle TA (baking soda) and CYA next.
 
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