Tap water pH issues

[el cheapo]

I bought a very small AGP recently. Just after my basic test kit arrived (Cl, Br, pH) and before I filled my pool I tested my tap water and it came in around what I might expect 1 or 2 Cl and 7.8 pH. Two weeks later I am finally ready to fill my pool and after I get it all filled, I test the Cl and pH and get essentially zero Cl and pH that is above 8.2. Is this possible? To be sure I checked the straight from the tap and am getting the same as I am out of the pool (high pH and low Cl). I am most worried about the pH. I used the pool calculator and added bleach to get where I wanted to be but I blew it on the pH front. I thought I was following the instructions on the pH decreaser (sodium bisulfate) but apparently I added too much and now the pH is below 6.8

So my questions are, is this possible/normal for city water to change so much and have such a high pH?

Also, should I now add Borax to get the pH back where I want it? Or should I just replace water?

Soon I am going to be adding Dichlor (for Cl and CYA, it is in the mail due to arrive in 2 days) which will also decrease my pH. Will all that Borax cause other problems?

Thanks!!

 

[yeggim]

PH is contingent on TA (total alkalinity). The further you are from 80 to 120 TA, the harder it is to predict what will happen when adding acid or base. It's usually wise to add a little less acid or base than called for and retest. Especially if you don't have an accurate TA number.

Borax causes no problems that I'm aware of but if your TA is low you might be better off adding soda ash (washing soda).

 

[Bama Rambler]

Without knowing what your TA is, it's really hard to predict how much acid or base it's going to take to move the pH. I'd add about half as much borax as the Pool Calc says to and see what that does to the pH. If it brings the pH up about where you want it just adjust the TA in the Pool Calc down the amount of borax matches what you added. It won't be nearly as accurate as knowing the actual TA, but it'll get you by with adjusting the pH.

Post back what your extrapolated TA is.

 

[yeggim]

Bama, that is pure genius. I can see that method being very useful for pool volume.

 

[Bama Rambler]

Thanks, Sometimes you have to think outside the test kit!

 

[el cheapo]

okay here is what I did so far. My basic test kit only goes down to 6.8pH. My reading was below that. I replaced some water and aerated until I got my pH up to an even 6.8. Then I added 3/4 cup or 6oz (by volume) of Borax, which is just less than half the amount pool calculator suggested. Ran the filter waited 30+ minutes. Now my pH reading is off the chart on the other side! Close but definitely more purple than the highest reading of 8.2.

My thoughts are that perhaps I have a little less water than the pool's capacity so my pool calc volume number of 1018gal. might be a little high though I would be hard pressed to guess-timate a better number.

As you suggested I played with the TA numbers to triangulate what TA would be required for me to have 6oz of Borate take me from 6.8 to 8.3 and I get a TA of 42. Does this seem possible? It would might explain the wild swings in pH even when I am using half the suggested dosage.

 

[Bama Rambler]

It sounds like you may have a couple of things going on. You're pool isn't as large as you think and your TA is low. A low TA will cause the pH to swing.

Try using washing soda next time to adjust it.

 

[el cheapo]

I am topping it off right now

Where do I get washing soda?

Thanks!

 

[Bama Rambler]

Your local Wallyworld or grocery store will usually have it. Don't confuse it with baking soda.

 

[el cheapo]

Well that did it. I added some washing soda and the pH has settled right down. In fact I think the just entering the estimated TA into the Pool Calc has really helped.

Thanks!!

 

[Bama Rambler]

Great! I'm glad it was an easy solution! (get it? )