First mistake - added too much CYA

I was aiming for a CYA of 40 in my new gunite pool. I started with 0 and added 5 lbs. That got me to 20 according to Ben's test kit. I did not know I was supposed to wait several days before retesting. The next day I tested and added another 2.5 lbs of CYA. Today I rechecked the CYA level and now I'm at 80!. I'll retest again tommorrow to confirm this reading.

The pool is about 18 to 20K gallons.
Should I just increase the Chlorine levels from 2 to 3 to around 5 or 6ppm?

Will the CYA levels drop after a while as I top off the pool water lost from evaporation and spash out - or do I need to take some other action?

Finally, how long should I wait between adding chemicals and testing for results?

You can easily maintain a safe, fun pool at 80ppm (of CYA). Just follow Ben's Best Guess table for the correct amount of Free Chlorine.

Refilling evaporation won't help you, but refilling after backwashing, rain water, etc, will. You have to dilute the CYA. If you want a CYA of 40, right away, you'll have to drain half your water and refill. You can run at high CYA for this season, drain it down in the fall and refill next spring.

Just run your pool at higher free chlorine levels and shock at higher levels and enjoy your pool.
Look through this thread for a post by ScottS, It has a copy of Ben's chart for what to run your FC and waht to shock at for varous levels of CYA:

http://www.poolforum.com/pf2/showthread.php?t=132

There is no easy way to lower CYA levels. You just need to drain partially and refill. If it's any consolation, most people with SWG systems run CYA at 60-80 and some pool stores recommend levels up to 100ppm(but not the corresponding levels of FC! I have the water test printouts to prove it.)
If your levels don't go above 80ppm you are actually within the "published

The main disadvantage of runnng high levels of CYA is that you are going to go thru a LOT of bleach!

If I've made any errors with this info will one of you real experienced bleach guys correct me?

Waterbear and Mshumack,

I'm not so sure that higher CYA levels will consume more Bleach, They will require you to hold your FC at a higher level to be effective, but I'm not sure it will actually consume more.

If your CYA is 30. you will keep your FC normally around 3ppm. Let's say 1 gal of bleach would raise your ppm by 2, so when your FC goes to 2ppm, you put in a gallon and your FC now is 4ppm.

Now your CYA is 90. You will keep your FC normally around 7ppm. That same gallon of bleach now raises your FC to 9ppm. You're not consuming more, you are simply holding a higher PPM number to make the Cl more effective.

I'm not sure anything definitive has been determined on that subject, but that's been my anecdotal experience.

Dave S.

I have a swg now in my pool/spa so I have no experience with bleach other than using it as a shock in my old (pre pool) portable bromine spa. It just seems to reason that to raise the FC to a higher level it will require more bleach. You are probably right about not needed more to keep it there since at higher CYA levels more of the chlorine is 'stablized' and the amount of available chlorine that gets eaten up by the chlorine demand would stay pretty much the same. Makes sense when you think about it and your empirical evidence back it up!
Ben or anyone else who REALLY knows what's going on with this care to enlighten the masses?;)

After 30 days (about 3 more weeks) I will activate my SWG. Hopefully I will be able to adjust the Chlorine levels to the higher levels to work within the range of the higher CYA level.

Waterbear said in his (your) post that it is okay to run higher CYA levels in a SWG pool. Does this mean I also need to add more salt (higher concentration) or just increase the percentage of chlorine generated?

thanks all for responding.

No, run the SWC in the manufacturer recomended range of salininty. You'll have to turn the dial up to get more Cl production.

Michael

duraleigh,

Thanks for the post because I've wondered about this.

CYA ties up a certain amount of chlorine, right? It protects that chlorine from the sun but also prevents that chlorine from serving as a sanatizer. The way I've pictured it, the chlorine that's available for sanitization is the chlorine that's not being tied up, in any way, by CYA. If that's the case than the chlorine that's available to sanatize would be unprotected from the sun. It can't be that simple because, if that where the case, there'd be no reason to have CYA in the first place. Somehow, it seems that a certain amount of CYA is beneficial even to the Chlorine that's not tied up to the point where it can't effectively sanatize.

Does that make sense? I'm thinking of this on a very basic level (sort of like a molecule of CYA binds to a molecule of Chlorine). There must be a good explanation for why a certain amount of CYA is beneficial to the chlroine overall. Can anyone explain this?

I've wondered why a high CYA level (50 or 100 or whatever) is really that big of a deal as long as you adjust your chlorine levels as Dave described in his post.

CYA doesn't consume chlorine, but it does slow down it doing it's breakdown--a 2-edged sword.

There's NOTHING wrong with running higher CYA if you use the correct Free Chlorine level. It's just fine and won't consume more chlorine once you reach the ideal level. You just need a FAS-DPD test kit for FC--Ben's kit has it and there are some others out there, too.