First fill - need to reduce very high TA

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freetime

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Jul 18, 2014
37
near London, UK
Hello all!

Been lurking on TFP quite a while and have learned a lot...thanks to all who contribute to such a great forum!

Did first fill on our dinky 10' Vinyl AG about a week ago, been adding and testing as per pool school but I have a couple of questions about reducing TA to keep the PH rise in check.

My first problem is getting an accurate measure, because TA and PH seem to be off the top end scale of my tests (TA 180 and Ph 8.4 respectively) However my water company rather helpfully provide some very detailed info about my water on their website - mine is TH 303 and CH 120. So I used these numbers in poolmath (BTW I know TH is not strictly the same as TA but at this level it's close enough!) and have been adding the doses of MA. For now, I'm also using Dichlor as a sanitiser to build CYA, I guess the Dichlor should be PH negative too?

After adding MA, the Ph does seem to drop a bit to about 7.6 - 7.8 but when I test again a couple of hours later, it's back at/above 8.4

Question is, should I just try increasing the MA dose until I get down to Ph 7.2? how quickly should I add more MA? At the moment it seems that the Ph is creeping back up in the space of a couple of hours! I'm guessing that with my high TA, the risk of overshoot is quite low (at least for the time being) but I'm new to all this......!

Thanks in advance!

Edit to add:

FC: 3
CC: 0
CYA: 10, based on 6% CYA per 10% FC Diclor added but I don't have a test to check!

Water is crystal and the pool is clean
 
Richard320 said:
Just keep doing what you're doing. Each time you lower pH, you're lowering TA, and each time it should require less acid than the time before and the adjustment will last a little longer.
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Your advice was spot on - I had been tempted to add more MA, but now I'm glad I didn't!

After the third addition of MA, the PH dropped down to 7.2, and only drifted back to 7.7 after the whole weekend, and lots of aeration. So it looks like it's slowing down already, just like you said.

I guess I should wait until PH hits 7.8 before adjusting again?

Thanks again!
 
timerguy said:
TH is total hardness?? I'm wondering whether that has anything to do with TA. And on a first fill? Your fill water has a high TA.
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Yup, TH is total hardness.

I now found a more detailed report from my water company that shows TH as 303 and separately TA as 334.

From what I have read TH is just the Calcium Carbonate bit, the TA figure includes the TH and various other stuff on top. Most of southern UK sits on calcium carbonate bedrock (i.e. Chalk) so I guess it's not surprising our water is full of it!

I'm thinking the sky high TA may explain why many people have problems with white cloudy pools in my area. Private IG pools are not too common here in the UK but AG and Intex type splashers are getting very popular. It's usual to drain for the winter and fill each year, so even if pH is adjusted from time to time the water never actually gets properly balanced.

I already used about twice as much acid than comes in a typical chemical kit, and I'm still not there yet! Most people just keep chucking more and more chlorine in and wondering why it isn't working
 
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