Why BBB Method?

[brittmer]

Evaporation has no effect on CYA. Using the pucks in my pool adds about 7.5ppm per week, so it would be insanely high if I let it go. If splash out and backwashing exchanged 10% of my water every week (not even close), my CYA would raise 7.5, and drop 10% of whatever the CYA concentration was, which means it would continue to climb until it got around 75ppm.

In reality, my weekly water loss is nowhere close to 10%, so my level would just keep climbing. If you are relying on a pool store to tell you your CYA is okay, they are lying. They can't test over 100ppm, and as far as they are concerned, 100ppm is great.

Evaporation does help because then I need to add new water to the pool.
I test cya myself and most years I can keep it around 60-85 fairly easy.

[chem geek]

Evaporation CONCENTRATES the CYA even higher (the same amount of CYA still exists, but is in a smaller volume of water after evaporation) and then adding new water DILUTES that same CYA to exactly the same value it was before evaporation. The net effect from evaporation and refill is NO CHANGE in pool chemical concentration (not just CYA, but CH and everything else).

Having CYA near 60-85 is fine if you are willing to keep your chlorine level up at around 8 ppm FC (minimum of 5 ppm FC), but you will be using a lot more chlorine every day by doing that and I suspect that using pucks you aren't keeping your chlorine that high. That means risking getting algae. You can avoid that by using weekly algaecide (PolyQuat 60), but that's expensive. The main purpose of BBB is to maintain the pool inexpensively.

Believe me, if there were an inexpensive source of slow-dissolving solid chlorine that didn't have CYA in it (or calcium either), then I'd be using it as you are right it would be more convenient, but there isn't. With a pool cover, however, one can cut down the chlorine loss per day such that you only need to add liquid chlorine (bleach or chlorinating liquid) every 3 days instead of every day.

Richard

[brittmer]

Evaporation CONCENTRATES the CYA even higher (the same amount of CYA still exists, but is in a smaller volume of water after evaporation) and then adding new water DILUTES that same CYA to exactly the same value it was before evaporation. The net effect from evaporation and refill is NO CHANGE in pool chemical concentration (not just CYA, but CH and everything else).

Having CYA near 60-85 is fine if you are willing to keep your chlorine level up at around 8 ppm FC (minimum of 5 ppm FC), but you will be using a lot more chlorine every day by doing that and I suspect that using pucks you aren't keeping your chlorine that high. That means risking getting algae. You can avoid that by using weekly algaecide (PolyQuat 60), but that's expensive. The main purpose of BBB is to maintain the pool inexpensively.

Believe me, if there were an inexpensive source of slow-dissolving solid chlorine that didn't have CYA in it (or calcium either), then I'd be using it as you are right it would be more convenient, but there isn't. With a pool cover, however, one can cut down the chlorine loss per day such that you only need to add liquid chlorine (bleach or chlorinating liquid) every 3 days instead of every day.

Richard

Good point as usual chem geek. I stand corrected.....as usual :-)

[CarlD]

If what you are doing is working for you, then it's working for you. We all have to compromise somewhere to ensure our pool is maintained the way we like it.

But it is a fact that evaporation will not reduce CYA. Splash-out and backwashing can, though.

The bottom line is it is your pool and you make all the decisions about it. We simply make suggestions based on what has worked for us and thousands like us.

If by whatever means you control CYA so you are happy with it, then, by all means, keep using pucks.

But I once went away for two weeks and left 4 floaters in my pool full of pucks. When I came back, my pool was clean as a whistle--algae free, my FC was up, but my CYA had gone from 30 to 60, and my pH was below 6.8--took 4 boxes of Borax to get it back up. It was then I learned that pucks are also EXTREMELY acid.

[waterbear]

IF you don't have a cartridge filter or a non backwashing DE filter.
IF you have a short swim season and winterize your pool (which means a partial drain, usually)
THEN using pucks in a feeder usually does not present problems with CYA getting too high too quickly.

IF you have a cartridge or non backwashing DE filter, an extended swim season, and live in a climate where you don't have to winterize your pool (or any combination of the above) then, IMHO, using pucks will lead to elevated CYA levels before the swim seaon is over and you might find that you have outbreaks of algae a few months into it (Could there be cause and effect why most Mustard Algae outbreaks are seen around August?)

Just my 2 cents!