Why Dry Acid is bad for a SWG?

[AK-]

I'm not sure if The Deep End is the right place for this question, but it is somehow related to chemicals and it is definitively not a must know to own a pool.

I have a bunch of Dry Acid that I brought when I ordered my pool (before TFP). I don't have a SWG, but I'm considering to get one in next few years if prices ever get back to "normal".

My understanding is that long term use of Dry Acid will increase sulfates levels on the water causing premature SWG cell wear/failure. Is that correct? Is there any other reason?

Is the assumption usage of Dry Acid before (even years before) installing a SWG will affect the SWG down the road?

 

[Texas Splash]

You have the right thoughts. The link below does a good job expanding on the subject.

Acid - Further Reading

www.troublefreepool.com

 

[AK-]

You have the right thoughts. The link below does a good job expanding on the subject.

Acid - Further Reading

www.troublefreepool.com

Humm… I read that before… I guess that was the source of my assumptions and I did not realize it.

 

[Texas Splash]

Humm… I read that before… I guess that was the source of my assumptions and I did not realize it.

And here I was thinking I was giving you a gem of knowledge. Ha. Maybe @Donldson has more to expand on.

 

[mguzzy]

So you are wondering if you use dry acid now.. whether it will affect your SWG that you are planning for in the future?... hmm I don't know who long that sulfates effect lasts.

 

[mknauss]

I don't know who long that sulfates effect lasts.

Sulfates are in the water until the water is drained and replaced with fresh water.

 

[mguzzy]

Sulfates are in the water until the water is drained and replaced with fresh water.

Right, but they don't break down into some other chemical compound over time that is not deleterious to SWG plates?... I'm guessing no.

 

[mknauss]

Right, but they don't break down into some other chemical compound over time that is not deleterious to SWG plates?... I'm guessing no.

No. The sulfates themselves impact the rare earth minerals on the plates.

 

[Donldson]

Here's a helpful post by @JoyfulNoise that I think covers some of why the use of dry acid is a bad idea all around, not just when using an SWG:

One pound (16oz) of dry acid per week to 9,000 gallons of water is adding 10.7ppm sulfate ion. Evaporation and refill is not affecting any chemical level because you’re not removing water. So if your season lasts 4 months, you’re adding roughly 160ppm sulfates. Sulfate-attack of concrete structures starts at 300ppm (give or take) and the sulfates are reducing the useful life of your SWG by contributing to excess corrosion of the metal-catalyst coating. Eventually your SWG is going to start spitting out white crystals that are a mix of calcium carbonate and sulfate. While using liquid acid (muriatic acid) is a bit more cumbersome than dry acid, you avoid all these issues. When handled properly, there is nothing dangerous about using MA except for the acidic smelling vapors which, despite some people’s over-reaction to it, is not dangerous when in an open outdoor environment. Your nose can usually detect smells and chemicals well before they are ever dangerous to your body.

Remember that the metal corrosion is not just in an SWG cell but also the metal in a heat exchanger of a heat pump and in the frame of an above ground pool. So yes, you would be setting yourself up for problems if you convert to SWG later, but you're also setting yourself up for the possibility of an early demise of your heat pump and the pool itself.

Isn't it interesting, BTW, that the problems pool stores claim comes from saltwater actually is rooted in the sulfate containing and acidic products (chlorine pucks) they sell to virtually everyone? Makes you wonder

 

[JoyfulNoise]

Your pool volume is fairly small and you live in NJ. My suggestion would be to simply drain and refill your pool when you get your new SWG and start fresh. Then you really don't have to worry about any of the dissolved solids in your water.

I recently drained about 11,000 gallons of water out of my pool and replaced it with "fresh" municipal water (boy did that water bill hurt when I got it ...). My previous water was still very manageable even after 8 years of buildup. But boy did swapping out 2/3rds of water really change the feel of it. Even after adding back in all the CYA, borates, salt, etc, the "new" water felt better than the old water. Out west here we don't get enough rain, so periodic draining does help to keep the water feeling nice. Back East, you guys get a lot of rain and so it's much easier to deal with TDS issues.

 

[AK-]

Early on I used about 1 1/2lb of Dry Acid... Since them I had about 500gal of water replaced (due to splash-out, a leak on a union that I was too lazy to fix right away and a lot of rain) and only used MA.... I guess that is not going to be enough sulfates to be an issue considering I'll have to drain about 1k gal to close come next fall, plus any splash-out/rain/refill along the way.

I also filled with municipal water. My first 25k gal per quarter are not expensive at all, but after that it gets salty pretty quickly. I timed my filling to fill half of it on the day before the township came to read my water meter to split the usage between quarters.

 

[phonedave]

Your pool volume is fairly small and you live in NJ. My suggestion would be to simply drain and refill your pool when you get your new SWG and start fresh. Then you really don't have to worry about any of the dissolved solids in your water.

I recently drained about 11,000 gallons of water out of my pool and replaced it with "fresh" municipal water (boy did that water bill hurt when I got it ...). My previous water was still very manageable even after 8 years of buildup. But boy did swapping out 2/3rds of water really change the feel of it. Even after adding back in all the CYA, borates, salt, etc, the "new" water felt better than the old water. Out west here we don't get enough rain, so periodic draining does help to keep the water feeling nice. Back East, you guys get a lot of rain and so it's much easier to deal with TDS issues.

Yeah, there I times I have to drain water because I have too much from rain and it is above the top of the skimmer opening.