Added sulphuric acid to saltwater pool

[Blakrsirch]

I just realized I’ve been adding sulphuric acid to my pool for the past few weeks. Maybe 1-2 gallons in total.
Is this going to Hurt the operation of the saltwater generator? One place I read said I have s to drain the pool!? Other people seem to say you can use either acid. So confused.

 

[JoyfulNoise]

Where did you get sulphuric acid from?? Not a common chemical sold to the public. Do you know what strength it was?

Sulphates are not good for plaster or SWGs but it depends on how much is in the water. Typically you don’t want more than 300ppm to avoid sulfate-attack of cementitious surfaces.

You likely don’t have to drain the pool. Since your location says FL, you should get ample fresh water exchange to offset the sulfates. If you backwash your filter, you can simply backwash more frequently to help along the dilution process.

 

[JamesW]

However, both local pool stores here in Jupiter FL strongly recommended sulfuric, saying that sulfuric acid will not lower the alkalinity, whereas muriatic will.
Muriatic vs Sulfuric acid

Some places push sulfuric acid over muriatic acid. Typical strength is about 38.5%.

Jupiter's moon Europa has a lot sulfuric acid on the surface and Jupiter, Florida pool stores prefer sulfuric acid. Coincidence? I think not.

 

[Foonly]

The Pinch-a-Penny near me sells both. I believe they told me that the muriatic is about twice the strength of the sulphuric. Muriatic acid is also known as Hydrochloric Acid, HCl. It seems to me that using an acid with Chlorine in it would be more compatible with pool chemistry.

Chemistry was a long time ago for me too, but I as I remember it, pH is a measure of the concentration of Hydrogen ions (H+), on a logarithmic scale, with pH=7 meaning the water is neutral. The opposite of acidic is basic. The confusion arises because "alkaline" is sometimes used as a synonym for "basic", though this is not strictly proper chemical terminology. Adding an alkaline substance to water will create negative hydroxide ions (OH-) which cancel out the H+ ions because H+ combined with OH- is just H2O, which is neutral. Acidic water (pH < 7) just has extra loose H+ ions dissolved in it.

When pool chemists talk about Total Alkalinity I think they are talking about something else, about the buffering ability of the water to resist changes in pH. If your pool does not have enough TA, then the pH will swing up and down a lot.

 

[JoyfulNoise]

Some places push sulfuric acid over muriatic acid. Typical strength is about 38.5%.

Jupiter's moon Europa has a lot sulfuric acid on the surface and Jupiter, Florida pool stores prefer sulfuric acid. Coincidence? I think not.

At that concentration it would only take about 1-1/2 gallons of sulfuric acid per 10,000 gallons of pool water to push you up near 300ppm SO4.

OP, can you post some info on the product you used, how much you added and what size (volume) your pool is?

 

[JamesW]

I get about 53 ppm sulfate per gallon of 38% sulfuric acid added to 10,000 gallons.

 

[JoyfulNoise]

I get about 53 ppm sulfate per gallon of 38% sulfuric acid added to 10,000 gallons.

Yes, you are correct. I forgot to convert gallons to liters along the way in one calculation....

So 53ppm per gallon of 38.5% H2SO4 added to 10,000 gallons of water.

My suggestion would be just to do some hard backwashes more frequently and drain down the pool an inch or two before a heavy rainstorm. Over time, the sulfates will just dilute away. Should be no harm to your SWG.

 

[Blakrsirch]

Thanks for all the replies. It was 38% sulfate. I thought I was buying muriatic. They were all in the same shelf and the type of acid was actually in small print. I’m lucky I happened to look closely at the bottle last time I added it!

im guessing I did one gallon but it could have been two. I have a 20000 gallon pool three months old.

My my main concern is that I’m having consistently low chlorine even though the swg is on 100% and the stabilized level looks ok. From the Wikipedia article on swg’s it sounds like the sulphate ions poison the swg somehow?

But hopefully you guys guys are right and it will dilute over time.

 

[mknauss]

My my main concern is that I’m having consistently low chlorine even though the swg is on 100% and the stabilized level looks ok.

Can you fill out a signature so we know about your pool and equipment? See Pool School - Read This BEFORE You Post

If your SWCG cannot keep up you may have algae and your chlorine load is higher than it can produce. Do you have a full set of test results you can post? How do you test your pool water chemistry?

Take care.

 

[JamesW]

The only problem that sulfates might cause in the cell is scale. As long as the cell stays clean, you're fine.

What are your chemistry readings?

 

[Blakrsirch]

I don’t have access to my readings right now. I got them tested at a pool store. Nothing was out of the ordinary except free chlorine was below the low range. It sounds like I should just keep an eye on it for now.

It’s not cloudy at all so hopefully no Algue. It’s getting a ton of use so maybe that pulls down the chlorine too?