lower TA with MA

[Whidster]

I just chatted with the pool guy that seems to be in sync with this site. I was looking for a fountain to aerate. He made the following suggestion and I wanted your opinion:

Turn off system.
Add 8 gallons of MA
Wait 24-48 hours while TA outgasses
Test TA -- should be near 0
Add EZ PH (sodium hydroxide) (40 bags) to bring PH back up

He says this is the fastest way.

I have gotten my TA down from 250 to 220 by MA/Aeration method. Would his way be safe and quicker?

 

[JasonLion]

That is a terrible idea. 8 gallons of muriatic acid would drop your TA to zero right away, which is something of an over correction. It would also lower the PH so far that there would be damage to the vinyl liner, and most heaters, not good at all. No need to wait 24-48 hours, that will just make the damage from the low PH worse.

Also, sodium hydroxide is caustic soda, which has caustic in it's name for a good reason, it is not very safe to handle (well, only a bit worse than muriatic acid).

 

[JohnT]

I just chatted with the pool guy that seems to be in sync with this site. I was looking for a fountain to aerate. He made the following suggestion and I wanted your opinion:

Turn off system.
Add 8 gallons of MA
Wait 24-48 hours while TA outgasses
Test TA -- should be near 0
Add EZ PH (sodium hydroxide) (40 bags) to bring PH back up

He says this is the fastest way.

I have gotten my TA down from 250 to 220 by MA/Aeration method. Would his way be safe and quicker?

That's a fast way to damage your pool and will have very little effect on the TA level in the long term. The MA will sink to the bottom and stay there until you turn the pump back on. It's a very bad idea and won't work. Check out the pictures in this document http://z6.invisionfree.com/San4um/index.php?act=Attach&type=post&id=14034925 showing a dyed muriatic acid addition to a pool with no circulation.

 

[Whidster]

Glad I asked! I am going with your instructions, but thought I'd run it by you.

Once I get my FC down is there any reason not to swim with the TA high?

 

[JasonLion]

TA doesn't directly affect swimming. As long as PH and FC are good you can swim.

 

[ThePoolNinja]

Never let your TA get that low, as the others have stated. If your TA is 220 right now, in a 20k gallon pool, it should only take 2-3 gallons of MA to lower those numbers down. But keep an eye on the PH as you lower your TA.

 

[chem geek]

Every gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid) in 20,000 gallons of your pool water will lower the Total Alkalinity (TA) by 25 ppm no matter how it is added. So as others said, he is adding way too much too quickly. 8 gallons would wipe out 200 ppm TA and the pH would plummet. If your starting TA were <200 ppm TA, then the pH would plummet below 4.5, but it's actually much worse because he would have you add the acid with no circulation so it would locally get to very low pH as others have stated even though your overall TA is >200. It does seem he calculated to try and not completely wipe out the TA, but the pooling of acid without the circulation is a big risk to damaging the liner.

At least he realized that raising the pH with sodium hydroxide would not increase carbonates the way that pH Up (sodium carbonate) would do.