Outdoor Pools without CYA

[pinguy]

I managed a commercial pool for a very short time last year, mostly as a favor when the person doing it quit suddenly.

One thing I was surprised by, is that several people I dealt with to purchase chemicals/equipment told me that outdoor commercial pools generally do not use CYA. One large commercial pool distributor told me they stopped selling it because no one bought it. Another distributor told me the health department didn't allow CYA in commercial pools (not true in my area, they just limit it to 50PPM).

How is this possible? The only alternative I can think is a very low FC level kept stable with a stenner and very good circulation. However that seems like a very fragile situation to me, should there be a high bather load and/or super sunny day.

I'm only asking out of curiosity, I'm a very happy CYA user myself.

 

[Donldson]

My guess would be ORP controlled direct chlorine gas injection, that would seem the easiest. It would be wasteful and as uncomfortable as any pool with no stabilizer, but if well maintained it could work successfully.

 

[JoyfulNoise]

Yes, there are many municipalities that regulate the amount of CYA allowed based on the faulty notion that CYA adversely affects CT kill times. The studies that showed that reached flawed conclusions because they attributed the low kill times to the presence of CYA itself rather than understanding the underlying buffering chemistry of FC & CYA. Once the data in the studies was controlled for FC/CYA ratios, kill times were easily correlated to what TFP would teach as adversely high CYA levels. Richard looked into this some time ago and I believe there are some posts on the subject.

As for how, well you've guessed it - ORP controlled direct chemical injection. I doubt it's chlorine gas except in the most high-end cases. It's probably either on-site generation of liquid chlorine or just a giant LC storage tank. For pH control, one would use CO2 injection as it is safer to handle than MA. Then there would likely be secondary oxidation sources with the use of a large surge/treatment tank for ozone or peroxide/UV injection.

 

[pinguy]

As for how, well you've guessed it - ORP controlled direct chemical injection. I doubt it's chlorine gas except in the most high-end cases. It's probably either on-site generation of liquid chlorine or just a giant LC storage tank. For pH control, one would use CO2 injection as it is safer to handle than MA. Then there would likely be secondary oxidation sources with the use of a large surge/treatment tank for ozone or peroxide/UV injection.

I suspected the supplier stopped selling bulk CYA to attempt to sell me an ORP system.

What a terrible way to run a pool, though. Uncomfortable, fragile, and expensive. I imagine the general public's bad feelings about chlorine and it's harshness stem from public pools with no CYA.

 

[JoyfulNoise]

One of the many reasons why I don't swim in YMCA pools....