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Can't Get Ph Down


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I have been a loyal Dichlor-then-bleach user for over a year now and usually everything goes as planned.

Just did my Spring empty and refill, so I have a new tub of water.

My current readings are

CH 170

TA 50

PH who knows, but its a really deep read.

50ppm of Borates

I just tested it and these were my readings. PH has been high throughout the process.

Thinking high FC levels were giving me false PH readings, I let the FC drop to 1ppm, which is was 10 minutes ago

Buy my PH is still deep red. I'd guess 8.4 or more.

I don't want to add anymore PH down because I don't want my TA to go any lower.

Any thoughts?

425 gallon tub at 104 degrees.

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Are you using a different source of bleach than in the past? You'll have to use acid to lower the pH and if that lowers the TA and you want it higher, then baking soda will raise the TA. If the source of the pH rise is from excess lye in the bleach, then the pH and TA would both rise though you might not notice the TA rise unless the pH went way up. So normally, adding acid to compensate for excess lye in bleach won't have the TA change much.

I also assume you don't have a lot more aeration now compared to before, right?

If all of this is just after a fresh refill, then don't worry about having to add acid to get the pH down and then some baking soda to get the TA where you want it. Just see what happens from this point forward after you've got things the way you want.

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Are you using a different source of bleach than in the past? You'll have to use acid to lower the pH and if that lowers the TA and you want it higher, then baking soda will raise the TA. If the source of the pH rise is from excess lye in the bleach, then the pH and TA would both rise though you might not notice the TA rise unless the pH went way up. So normally, adding acid to compensate for excess lye in bleach won't have the TA change much.

I also assume you don't have a lot more aeration now compared to before, right?

If all of this is just after a fresh refill, then don't worry about having to add acid to get the pH down and then some baking soda to get the TA where you want it. Just see what happens from this point forward after you've got things the way you want.

Thanks for the reply, you have to be the most helpful person on any forum.

I haven't gotten to the bleach part of the method yet. I'm only at 20 CYA on my way to 30, then I'll switch.

Does adding baking soda increase PH as well as TA?

If not, I'll get my PH down and adjust TA from there.

Thanks again

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Thanks for the compliment. We all try to help out here.

The baking soda raises the pH some but not too much. It depends on the pH. It raises it more if the pH is lower. I'd just lower the pH with acid to roughly what you want, probably near 7.5, and then (after measuring TA) slowly add baking soda to raise the TA (if needed) with the circulation pump on but not any jets (you don't want aeration when adding the baking soda). The key to not having the pH rise so much when adding baking soda is to add it slowly with enough thorough mixing to prevent it releasing carbon dioxide from being too concentrated in the water near the surface. Worst case, you might need to add a little acid afterwards, but that will have hardly any effect on the TA. This isn't rocket science and the pH doesn't have to be perfect -- just in a reasonable range.

One more thing to note -- when in the Dichlor phase, it should be a little like adding acid so the TA should slowly come down and the pH shouldn't be so high. Of course, you must have started out with very high pH from your fill water, for whatever reason. I'm just pointing out that for most people, the Dichlor phase will tend to keep the pH in check and slowly drop the TA after which they can adjust TA even lower as needed before switching to bleach. Just for the heck of it, if you're not low on reagents you might test the pH and TA of your fill water just to see what might have happened.

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One other possibility...how old is your pH reagent? I have seen phenol red 'go bad' and give inaccurate readings. pH reagent is cheap enough that this would be easy to check. IF your color is not one of the ones on the comparator then your reagent is probably bad!

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One other possibility...how old is your pH reagent? I have seen phenol red 'go bad' and give inaccurate readings. pH reagent is cheap enough that this would be easy to check. IF your color is not one of the ones on the comparator then your reagent is probably bad!

I can confirm that to be true because it happened to me, I use to keep the test kit on the window sill and the sun and heat effected them. The same is true for both calcuim hardness and TA tablets.

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