Filter pressure up after adding borax

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C

camueller

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May 11, 2016
491
Troy IL
Split from Adding Borax makes DE filter clogged. Zea3

Hi all, sorry to dig up an oldish thread, but I just went through the Borax process yesterday with my pool. I have a sand filter, but with DE added. I got up this morning and my pressure had shot up well over 25%. So I backwashed and the water looked fairly white. Had to have been the borax. My procedure was to take the required borax (4 boxes, since they are 65oz now instead of 75oz) put it in a bucket, and run water from the hose over it until it all spills into the pool. It wasn't necessarily all dissolved, but mostly. I don't even have a main drain, just a skimmer. Hopefully I didn't throw too much of it away by backwashing.
 
Re: Adding Borax makes DE filter clogged.

Did you lower your pH first?

Borax is very alkaline. In its solid undissolved form it can act like soda ash where it creates localized areas of very high pH. This can cause localized precipitation of calcium carbonate which takes a very long time to re-dissolve.

This is why the boric acid route is a lot better - mild lowering of pH and absolutely no scaling.


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Re: Adding Borax makes DE filter clogged.

Interesting, that kind of makes sense. My pH was 7.5 when I started to add it all. I added a gallon of acid, then 4 boxes of 65oz borax dissolved in a bucket. Now, the dissolving in the bucket took much longer than the gallon of MA being poured. So I would think that gallon of MA would lower my pH pretty well before I started adding the borax...but maybe not. And I do have hard water. The pool has a CH of 250, my fill water actually much higher unless I fill from my water softener.

In the future I do think I'll just order some boric acid. But this round I was impatient and didn't want to wait for shipping. Plus I had access to cheap MA and borax.

Live and learn perhaps. None of the guides I read on this topic mentioned anything about scaling being a problem with the borax route. Nor did I see anything about lowering pH first, just that it should be between 7.4 and 7.6. I guess the good news is I got some calcium out of the water. Hopefully the borates didn't bond with that, and also escape my pool. But I'll test the borates tomorrow and find out.

For now, when I was done with adding all the MA and borax, I waited 2 or 3 hours and tetested the pH. It was up at 8, so I added MA to bring it down to 7.5 again and that is where I sit as of right now. I haven't added any DE back to the filter yet, not sure if I should.
 
Scaling is a problem anytime you add a strong base to your water. Cal-hypo, soda ash, borax, etc, can all create localized high pH areas. Bases should always be pre-dissolved and/or diluted as much as possible and then broadcast slowly around the pool perimeter.

As for calcium and borates, there is no calcium borate compound that can form within pool water. So if any borates were lost, it would have been from backwashing out undissolved borax.

Honestly speaking, the adding borates sticky was written at a time when few people were adding borates and the only available source was 20 Mule Team Borax. Most people had no way of getting granular boric acid in the quantities needed to achieve 50ppm . So the borax/MA route was the easiest way for a DIY pool owner to get results. In my personal opinion, adding boric acid directly is much safer, faster, easier and less error prone than the borax/MA route and is well worth the tiny cost differential between them. Seeing as how 20 Mule Team is now being sold in smaller boxes at the same or higher price, granular boric acid is now the cheaper alternative.


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Well that makes sense then. Thanks so much for explaining. Assuming I'm happy with the borate thing, I'll definitely be ordering some boric acid to maintain my levels for the future, if only due to this scaling issue.

I assume it is safe to put some DE back in my filter by now, right? All the scale is hopefully gone?
 
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