CYA in a Bromine Pool

[CarlD]

For a number of years the SWCG folks, both pros and owners, have been aware that the "Best Guess Table" overstates THEIR required chlorine levels for the higher CYA levels required.

Normal CYA levels for them of 70 or 80ppm with FC levels of roughly 2-4 seem to easily keep their pools sanitary because the FC level is far more constant than in a manual pool.

But Ben's point of laying out practical, simple, and understandable steps to recommend is the equally valuable flip side of taking pool maintenance from alchemy to chemistry (the struggle we are all engaged in).

After all, most of us users aren't going to understand or care about molecular interactions by which bleach, which is not pH neutral, creates a reaction by the release of chlorine in exactly the opposite direction that zeroes it out. We WILL understand the bleach doesn't alter pH.

We want and need to advance the art and science of pool care, but to be useful we need to turn this into both practical steps and a clear decisive decision tree to follow to get to the ultimate goal:

A safe, sanitary swimming pool that's easy to maintain and is available for swimmers as much as possible.

That's why the China Shop is a great place, actually THE place to discuss theory, new concepts and experiments.

[chem geek]

That's why this thread is here in The China Shop.

I don't know whether the lower minimum FC/CYA levels for SWCG pools are due to the more consistent dosing or due to the superchlorination of some of the water passing through the cell. It's likely to be some combination of both. Obviously, the superchlorination doesn't do anything for algae stuck on pool surfaces and would only affect planktonic (free-floating) algae.

It would not be hard to have a separate recommendation/table for SWCG pools compared to manually dosed pools without having to go into detailed explanations for why. Since SWCG pools have the pH rise problem and since that is proportional to the SWCG on-time which is proportional to the daily chlorine demand which is proportional to the FC level assuming a constant CYA level, it is important to have the lowest effective FC level in order to minimize the rate of pH rise.

[CarlD]

It would not be hard to have a separate recommendation/table for SWCG pools compared to manually dosed pools without having to go into detailed explanations for why. Since SWCG pools have the pH rise problem and since that is proportional to the SWCG on-time which is proportional to the daily chlorine demand which is proportional to the FC level assuming a constant CYA level, it is important to have the lowest effective FC level in order to minimize the rate of pH rise.

All we need is one and then we can sticky it! I think that would be a GREAT addition!

[waterbear]

All we need is one and then we can sticky it! I think that would be a GREAT addition!

You mean like this?
http://www.poolforum.com/pf2/showpos...9&postcount=22

[CarlD]

Nope. A table like the "Best Guess Table" only a "SWCG Best Guess Table".

[waterbear]

Nope. A table like the "Best Guess Table" only a "SWCG Best Guess Table".

For an outdoor pool with a SWG:
CYA 80-100 ppm (use SWG manufacturer's max number)
FC 3-5 ppm
Shock, if and when needed to 20 ppm with bleach

These numbers work.

I would also add:
TA 60-80 ppm
pH 7.6 to 7.8
CH 350 to 400 ppm (for plaster and fiberglass)
borates 50 ppm

These parameters will give the best pH stability, which will vary with each pool because of such variations as water features, assuming cured plaster.

No need for a chart since keeping the CYA at 80 or 100 ppm is important for pH stability since it translates into less cell on time.
One set of parameters is all you need based on the CYA of 80 or 100.

[CarlD]

That's a really, really small table, 'Bear!

Reminds me of the world's shortest poem called:

"Fleas"

Adam
Had'em.