adjusting alkalinity

Problems relating to pH and total alkalinity. Increase ph, increase TA. Reduce pH, reduce TA. pH chemistry advice and techniques.

adjusting alkalinity

Postby GABE THE POOL GUY » Thu 19 Jul, 2007 18:19

im currently new to pool matienence and most of my pools are now high to really high in alkalinity / ph ta of 120 to 280. most of my pools have a ph of 7.2-8.0. i was told to adjust my alkalinity correctly is to make sure my ph is minimum of 7.4 and to pout 1 gallon of muriatic acid (30k gallon or more pool) in balls ( circles) in the deep end of the pool with the system off. i should wait 10 minutes then turn the system back on and brush the bowl of the pool where i poured towards the main drain and to keep the vaccum and chlor floater away from the pour . is this the correct way .. how much drop will i get from pouring acid to lower alkalinity with pouring 1 gal at a time .
thanx, gabe
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Postby Backglass » Thu 19 Jul, 2007 19:15

All methods will lower your ph & TA...but there are many myths and legends about HOW to pour acid claiming different results (acid ball, slug, walk the acid, etc).

That being said, there was an article in Pool & Spa magazine where a scientific study was done (rather than pool store urban legend) using different methods and the outcomes were all the same.

Me? I just pour it all in near my return with the pump running.
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Postby chem geek » Thu 19 Jul, 2007 21:13

To lower pH and TA together (mostly the pH), you just add the acid any way you like, but SLOWLY since it can be harmful (I pour slowly over a return where the skimmer is on the other side). For extra safety, you can add the acid to a bucket of pool water and then pour that in slowly.

To lower the TA, use the procedure described in this post. Aeration at low pH and adding acid to keep the pH low is the fastest way to lower the TA. Using an air compressor with a nozzle or pipe that produces lots of tiny bubbles works really well as do contraptions that pipe water from returns into shower jets to create bubbles. Get creative! It's fun.

As for how much acid lowers how much TA, it's not a simple formula, but if you give me the starting pH, TA and CYA and your goal pH and TA, I can tell you how much is needed for each step. I have a (complicated) spreadsheet that calculates this accurately (found here).

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