Sanitation without acid

[mmcr]

Here in Australia we’re just getting into summer and pool season, so I’ve started checking things more carefully and adding salt, acid etc.

There’s a company here that’s been around for a few years, who (amongst other things), promote a proprietary method of sanitation that doesn’t involve adding acid

I have a SWG and apart from salt at the start of the season, the only thing I regularly add is acid and CYA.

I was intrigued by their technology; of course they don’t reveal everything, which is fair enough, but I gather that you still need a SWG, fairly high salt levels, and bromine. They then say with their constant monitoring you’d only rarely need to add acid, and the pH is allowed to drift up much higher than normal for a salt pool (8+)

Does anyone have any ideas as to the science behind this ?

Their energy savings don’t add up for me, otherwise I’d have just signed up for their product. However if I could have a largely acid free pool chemistry that would be great !

 

[JoyfulNoise]

....However if I could have a largely acid free pool chemistry that would be great !

But you’d also have a bromine pool which is impossibly difficult to maintain without the SWG running all the time! Bromine, unlike chlorine, cannot be stabilized against UV loss so high sun and heat will use up the bromine generated by the SWG as fast as it produces it.

What’s wrong with adding acid? It’s perfectly safe when handled correctly and, at least here in the US, costs less than liquid chlorine.

Their science is a misunderstanding at best. When CYA is present in pool water, the pH doesn’t really matter as far as sanitation goes. The chlorine is just as effective at a pH of 7.2 as it is at 7.8 or 8.0. For bromine, the dissociation constant is higher (pKa) and so bromine in water is almost always hypobromous acid (HOBr) and very little hypobromite (less sanitizing power than HOBr). But, as I said, that matters very little.

The main reason to control pH in a swimming pool is for calcium saturation balance to avoid scaling, NOT for sanitation. If you have hard water and high pH, you will wreck your SWG cell regardless of whether you use bromine or chlorine. So the entire rationale for their “special process” is wrong.

 

[JamesW]

As long as you keep the pH and TA at the correct levels, you don't need to regularly add acid.

If you need to add acid on a regular basis, you're keeping the TA too high or the pH too low or both.

Try keeping the TA at 60 and the pH at 7.8 or 7.9. Maintain the cyanuric acid at about 60 ppm.

A SWG does not require constant additions of acid. A SWG does not cause pH rise. Any pH rise comes from carbon dioxide offgassing. Carbon dioxide is created by high TA and low pH (below 7.8).

I suspect that their "system" amounts to nothing more than throwing in a few pounds of sodium bromide in the water.

They claim that it's "proprietary" to hide the fact that there's nothing worthwhile or valuable going on.

What is the TA in the pool and the fill water?

 

[mmcr]

What’s wrong with adding acid? It’s perfectly safe when handled correctly and, at least here in the US, costs less than liquid chlorine.

Their science is a misunderstanding at best. When CYA is present in pool water, the pH doesn’t really matter as far as sanitation goes. The chlorine is just as effective at a pH of 7.2 as it is at 7.8 or 8.0.

Sorry I may have mis-represented them. Forum rules don't allow me to link to their site, but they say that whatever chemical mix they use allows them to run a pH between 7 and 8.5, though they generally allow it to drift up to 8-8.5, all while allowing sanitation and no scaling, crystal clear pool etc.

When I asked how do they do this with a high pH, their answer was 'advanced water chemistry and constant remote monitoring', but bromine was mentioned as part of the 'advanced water chemistry'. They install sensors, wifi switching and a gizmo that would turn my old standard single speed pump into an 'infinitely variable speed' pump.

They then monitor chemistry remotely, and adjust chlorinator and pump time as required. They say you need to add chemicals once or twice a year only (they send you what you need based on their monitoring). Their purported energy savings come from constantly monitoring weather and the pool balance, and spinning the pump and chlorinator up and down as required.

Based on their projected energy savings, it didn't make financial sense to me (I installed a large PV array instead), but I was intrigued by the acid-free water chemistry. I don't have an issue with acid, other than if I don't need to add it, it would be one less thing to do !

If you need to add acid on a regular basis, you're keeping the TA too high or the pH too low or both.

Try keeping the TA at 60 and the pH at 7.8 or 7.9. Maintain the cyanuric acid at about 60 ppm.

What is the TA in the pool and the fill water?

After not checking/adding chemicals over winter, my TA is high (currently 116), pH 8.5, CYA 51. Pool is 85000L

Looking at the Pool Math app, to lower the TA it suggests I should add acid to drop the pH to 7-7.2

Is there anything else to add other than acid to get the TA and pH down ? And what else can I do to avoid the up-swing in pH that I seem to get ?

 

[JamesW]

Once you get the TA down, the pH rise should stop. Don't try to keep the pH below 7.8.

 

[wireform]

Mmcr
Don't try to knock down the TA at once. Bring the PH down to 7.2 with MA then aerate to 7.6-7.8, when you reach ph of 8 drop again with MA this way gradually you lower the TA. When the TA moves into target level your PH swings will be alot less.