Low pH and TA

[cardiacmommy]

I got really super delinquent with our pool once it started cooling down. We threw a leaf cover over thankfully but nothing else for a while. Need to get the pool clear so we can close it before it gets too cold. Right now the weather is 50-60's during day and high 30s at night.

So my pool is of course GREEN but not too murky. Cleaned off the leaf cover and checked the water today.

pH is low = 6.8
TA is really low = 10

FC was like 3. CYA 60. I shocked it today, rechecked and it was still at 18, overcast cool day, don't know water temp but it was pretty cold. Got the sand filter running constantly. Hopefully keeping it at shock level I can have it cleared up and can close it.

Should I go ahead and get the pH/TA fixed too? I tested it before I shocked it. I know at shock level I can't really recheck it as I think it will show even lower. I have a whole bottle of pH Up that was given to us. Can I use it to raise the pH and TA?

 

[dmanb2b]

Sounds like you are on the right track. PH up will certainly do the trick for both TA and PH.

 

[cardiacmommy]

Thanks. Amazingly my FC has stayed at 18 all afternoon...just checked it again at sundown.

Should I go ahead and add the pH Up in the morning after checking my overnight loss?

Will I have to let my FC get down to normal levels to recheck my pH before closing?

 

[chem geek]

You won't want to use too much pH Up, assuming your pH is really 6.8 and not below (it might be lower and you now know it since 6.8 may be the lowest reading in your pH test). If your pH and TA are truly as you say (as well as CYA), then adding 15 ounces weight of pH Up (around 1 cup 5 ounces volume) will raise the pH to 7.5 and the TA to 26 ppm. If you add enough pH Up to get the TA higher, your pH will get too high.

Since you need to get the TA up a lot, I'd use baking soda or at least mostly use baking soda. If you add 90 ounces weight (about 9 cups) of baking soda in addition to the pH Up from above, then that would get you to a pH of 7.8 and a TA of 80 ppm. If you only added 115 ounces weight (about 11-1/2 cups) of baking soda and no pH Up, then the pH would get to 7.4 and the TA to 80 ppm. Note that the pH may get higher than I just described because there can be some carbon dioxide outgassing when you add the baking soda.

So, you could add some pH Up, say 10 ounces weight, and then after allowing to mix remeasure the pH. If it's significantly below 7.3 (i.e. still at 6.8) then you can add another 10 ounces weight and remeasure. That way, you'll only add pH Up until you start to get into a decent pH range above 7.0 and from that point you can use baking soda to get the rest of the way for the TA.

 

[cardiacmommy]

Thanks ChemGeek. I was going to use the pH up since that's what I have on hand and since I really have no desire to step in a grocery store this week! lol

Can you recommend how I handle this in regards to the current shock process? Because doesn't having the FC over 10 alter the true value of the pH?

 

[chem geek]

Yes, a higher FC complicates things because it affects the pH test directly (though it usually has the pH read too high; since yours is so low it's probably not getting affected much) and because the pH will drop as the FC level drops. However, you measured the pH and TA when the FC was perhaps 3 so those numbers are probably valid. If I start with those and with the CYA of 60, then getting the FC to 18 ppm using chlorinating liquid or bleach would have raised the pH to perhaps 8.0 if your pH was truly 6.8 and not lower. You might, for the heck of it, check the pH even though the FC is high. If the pH reads high, then ignore it -- it is probably high though not necessarily as high as it looks. If it instead still reads low like 6.8, then your pH was really around 6.4 (or lower) to start with.

If you were to add baking soda to raise the TA at this point, the pH wouldn't change much. The TA reading at a pH of 8.0 is higher than it will be at 7.5 (after the chlorine drops back towards 3 ppm) by only about 10 ppm. So adjusting the TA at this point using baking soda is not a problem. However, you really can't use your pH Up now if the pH is truly high -- that's why it would be interesting to check the pH it even when the FC is high.

 

[cardiacmommy]

Ok checked tonight. The FC is STILL 17 (guess I could add a smidge of chlorine to get it back to 18) I'm just suprised it's stayed within 1.5 for about 30 hours now. Granted it was cloudy and rainy today - but geez you'd think with a green pool it'd be dropping more than that????

The pH is still reading 6.8, so guessing it was really low to begin with. I got a TA of 20 this time. Hubby picked up 8 lbs of baking soda today, so between that and the pH up I should be in business.

 

[dmanb2b]

Any chance you could post a pic of the water for us? I'm wondering if this may be a copper isssue rather than algae? I'm doubtful you'd only lose 1.5ppm in 30 hours and the pool still be green due to algae

 

[cardiacmommy]

I can take one tomorrow. The clarity is not all that bad. Certainly not like how I opened it! We went at least a month with no chlorine in it (and to be honest, we used the pucks several times over the summer) Hubby tossed in some bleach last week (I have no idea how much, he didn't tell me he was doing it) then he also unplugged the pump over the weekend. Otherwise our FC would have been zero - hence why I assumed algae. Otherwise we have had the pump going 24/7. The leaf net has kept most of the debri out. I assumed some of that still broke down into bits of organic matter though, esp with no chlorine for a good while now.