How much chlorine?!

[Gruenegenes]

My pool is 19,000 gal, my CYA is 80 and this chart shows I need 46 ppm of FC to kill my mustard algae. I can’t even comprehend that level. Practically speaking, how many gallons of Cl should I plan to dump in my pool to achieve that FC level?

Chlorine/CYA Chart

EDIT: You will find a simplified and standardized version of this chart at Pool School, Chlorine / CYA Chart. Chlorine/CYA Chart by Chemgeek FC = Free Chlorine in parts-per-million (ppm) CYA = Cyanuric Acid in parts-per-million (ppm) CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd...

www.troublefreepool.com

 

[Jimrahbe]

G,

One gal of 10% Liquid Chlorine will increase your FC by about 5.3 ppm.. So to get to 46 ppm, you'd need to add about 9 gallons of 10% LC..

That said... why do you believe that you have Mustard algae? Also, this is exactly why we we almost always suggest that you lower your CYA to 30 or less before doing a SLAM..

Thanks,

Jim R.

 

[Gruenegenes]

G,

One gal of 10% Liquid Chlorine will increase your FC by about 5.3 ppm.. So to get to 46 ppm, you'd need to add about 9 gallons of 10% LC..

That said... why do you believe that you have Mustard algae? Also, this is exactly why we we almost always suggest that you lower your CYA to 30 or less before doing a SLAM..

Thanks,

Jim R.

Thanks for the info. Very helpful.

I believe I have mustard algae because it looks like mustard algae.

I was hoping to avoid draining my pool, but 9 gal is a lot of Cl. Can anybody estimate how many gallons I need to drain to bring my CYA to a proper concentration?

 

[Jimrahbe]

G,

More than half...

Thanks,

Jim R.

 

[JJ_Tex]

Also, make sure you are following the mustard algae SLAM properly. This is not just a dump x number of gallons of chlorine in your pool and be done with it. You have to follow the SLAM, which will take days/weeks, then the final 24 hours is at the elevated mustard algae FC level.

In reality you will need a lot more than the 9 gallons of liquid chlorine, but you will be adding that over time and not all at once. On the final 24 hours, you will be going from your elevated SLAM FC level so that jump will not take 9 gallons.

 

[Gruenegenes]

Are there any concerns for the plaster if I drain a portion of my pool? The pool is 8 months old and I recall the builder telling me draining would void warranties.

 

[Jimrahbe]

G,

You don't drain it and leave it drained, you immediately fill it back up. It should not have any effect on your plaster.

Thanks,

Jim R.