The scariest water I have ever seen in my life!

[Poolsean]

"I'd bet, if you did up the PP literature, you'd find that that's just what it claims, until you get to the really fine print"
You'll find the Pool Pilot lit says that the pH is near neutral but in no way do we claim that it will drive up the pH and that constant acid additions are needed. In fact you'll find that in my responses that I'm fairly suprised at some of the swg pool owners that use MORE acid than in a bleach pool.

[waterbear]

"I'd bet, if you did up the PP literature, you'd find that that's just what it claims, until you get to the really fine print"
You'll find the Pool Pilot lit says that the pH is near neutral but in no way do we claim that it will drive up the pH and that constant acid additions are needed. In fact you'll find that in my responses that I'm fairly suprised at some of the swg pool owners that use MORE acid than in a bleach pool.

Sean,
Correct me if I'm wrong here but the electrolytic generation of chlorine from salt water produces sodium hydroxide as a byproduct. The 'offline' units of the past had a separate tank for the waste lye to prevent the pH rise but the modern inline units like the PoolPilot (and the Aqualogic on my pool) do not and the sodium hydroxide is discharged into the water. I don't know if the concentration generated is higher than the amount found in the same amount of liquid sodium hypochorite needed to maintain the same FC level or not. I do know that my 6600 gal fiberglass pool does need acid about ever 3 weeks (about a pint and a half to two pints) to bring my pH down from about 7.7 back to about 7.4. I have never chlorinated this pool any other way than the SWG so I don't have anything to compare it to but SWGs DO cause the pH of a pool to rise! There is not way to get around the chemistry involved!

I have noticed that among my customers with SWGs the ones that are running lower CYA levels (and therefore higher cell outputs to maintain the chlorine) do seem to go through more acid and have more problems keeping the pH in line and new plaster pools with SWGs seem to go through a LOT of acid (then again, many new pools on trichlor do also!)

[Poolsean]

Although you've got the high pH of the Sodium hydroxide, you also have the low pH of chlorine gas (which instantaneously converts to 100% pure sodium hypochlorite - without the high pH nature) to keep it fairly neutral.
We typically say that if you just leave the pH alone for awhile, it will climb to about 7.8 - 8.0 and hover around there, and not much higher.

The Unichlor systems of old (the one you're describing with the waste Lye tank), were modified in the late 80's to reintroduce the lye as a pH balancer. They called this the diluter kit. Again, one side produced chlorine gas that was syphoned into the return line, whereas the caustic side was commonly drained, but then was used to return some sodium hydroxide back into the water, thereby increasing the pH back up from the low pH effects of the chlorine gas.

[waterbear]

Although you've got the high pH of the Sodium hydroxide, you also have the low pH of chlorine gas (which instantaneously converts to 100% pure sodium hypochlorite - without the high pH nature) to keep it fairly neutral.
We typically say that if you just leave the pH alone for awhile, it will climb to about 7.8 - 8.0 and hover around there, and not much higher.
Yep, my pH goes up to about 8.0 and stays if I don't add any acid.
The Unichlor systems of old (the one you're describing with the waste Lye tank), were modified in the late 80's to reintroduce the lye as a pH balancer. They called this the diluter kit. Again, one side produced chlorine gas that was syphoned into the return line, whereas the caustic side was commonly drained, but then was used to return some sodium hydroxide back into the water, thereby increasing the pH back up from the low pH effects of the chlorine gas.

thanks for the info!

[PatL34]

"I'd bet, if you did up the PP literature, you'd find that that's just what it claims, until you get to the really fine print"
You'll find the Pool Pilot lit says that the pH is near neutral but in no way do we claim that it will drive up the pH and that constant acid additions are needed. In fact you'll find that in my responses that I'm fairly suprised at some of the swg pool owners that use MORE acid than in a bleach pool.

Sean,

Agree with most of what you say here, except for the final sentence.

In fact you'll find that in my responses that I'm fairly suprised at some of the swg pool owners that use MORE acid than in a bleach pool.

There two reasons for using more acid than in a bleach pool.

1. The acid replaces the bleach component of the bleach pool.

2. A gunite/plaster pool will also use more because of the leaching from the walls.

Liner pools appear to use little acid, but still need it.

Pat