I don't really know what is going on. Our water is very hard and in the past it wasn't uncommon to see 250 for alkalinity when I first fill. I would usually use a tablespoon of muratic acid and it would bring it down in a minute to where I could balance everything out with my spa down.

Today I filled up for the first time since spring. I went through 3/4 of a cup of muratic acid and 1/4 cup of spa down and got it to 119. I just came home 4 hours later and it is testing at 285. Anyone know what is going on here or what I can try?

What is your pH? That's far more important.

The ph is 8. I can bring it down but when the alk goes back up so does the ph.

I would add enough muriatic to keep your pH into the 7's.....all the time. The TA will come down with it and will stay down as long as you continue to re-add muriatic as the pH rises. I imagine it is pretty common to see a pH rise in a spa because of the constant aeration

I am not a spa owner but I would think it is fine to let your TA seek whatever level it wants and you simply control pH.

Why do you think the TA is critical?

It makes the water smell bad

TA can't go back up on its own. The only way TA can go up is if something is added to make it go up. It can go up if the tub has a lot of scale because the scale can dissolve and add alkalinity.

It would help if you could provide the following information:

1)What test kit you are using.
2) Volume the tub
3) Ingredients of the Spa Down
4) Initial TA
5) Calcium hardness
6) Is there any rough calcium carbonate scale buildup on the sides?

1.) I am using AquaChek True Test
2.) 400 gallon Caldera Hawaiian
3.) Pool Pride ph reducer Sodium Bisulfate
4.) When I filled it yesterday initial TA was 287
5.) I don't know how to measure calcium hardness
6.) There are no rough calcium scale buildup

6 ounces of 31.45 % muriatic acid would bring the TA from 287 ppm down to 228 ppm. 2 ounces volume (3 ounces weight) of dry acid will lower the TA from 228 ppm to 206 ppm. So, I don't think that your second test result of 119 ppm could have been accurate. Your third test result of 285 would not add up either.

Test strips are not reliable, despite the apparent precision. I recommend that you get a good test kit such as the TF-100. The TF-100 includes a test for calcium hardness, which is important to prevent scaling.

You can use the pool calculator to calculate amounts of chemicals needed to adjust chemical levels.

When lowering TA, you lower the pH to 7.2 until the TA gets down to the desired level. I recommend using muriatic acid over dry acid.

Are you using chlorine, bromine or something else?

pool-school/lowering%20total%20alkalinity