“Normal” FCl loss during 24 hour period

seanauld

Active member
Aug 4, 2021
25
halifax, nova scotia, Canada
Pool Size
430
Surface
Fiberglass
Chlorine
Liquid Chlorine
Good Day Folks, apologies if this has already been asked/answered but I searched and did not find.

I have a 430 gallon hot tub, dichlor/bleach now, liquid chlorine 10.3%. CYA is a little higher than I would like @ 50 ppm., Al 100, pH 7.5, CH 150. Usually bring up to 4-6 ppm FCl and the CCl is always less than .5 ppm. I am finding that if the tub is not occupied , I am losing about 4-5 ppm FCl over a 24 hour period. Tub is 3 months old, water has been flushed once, pipe cleaner was used and the water is crystal clear. Wondered if there a norm for loss of FCl for unoccupied time. Concerned that I may have biofilm in the pipes perhap , thus the FCl consumption ?

many thanks
sean
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,686
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
The minimum FC level for a CYA of 50 ppm should be 4 ppm. FC/CYA Chart

If you are bring up FC to 4-6 ppm and losing 4-5 ppm, then that means the lowest FC over a 24 hr period is close to 0 ppm. So you should never let FC get below 4 ppm. So if you lose 5 ppm overnight, then you really should be targeting 10-11 ppm when dosing.

Also, what is the temperature of the hot tub? Higher temperatures mean more FC is loss over time.
 

seanauld

Active member
Aug 4, 2021
25
halifax, nova scotia, Canada
Pool Size
430
Surface
Fiberglass
Chlorine
Liquid Chlorine
Thank you, temperature currently is 100 F, ill raise the levels of free chlorine re: the CYA / chlorine chart, is the 24 hour loss of FCl reasonable to occur on a regular basis.
many thanks
sean
 

mas985

TFP Expert
LifeTime Supporter
May 3, 2007
14,686
Pleasanton, CA
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
It seems a bit high for a pool but a 100F spa is completely different. Not sure what would be "normal" for that. Raise the FC levels and see if the loss is reduced. If the loss increases, then it is probably due to the water temperature. This is one of the reasons bromine is often used in standalone spas.
 

seanauld

Active member
Aug 4, 2021
25
halifax, nova scotia, Canada
Pool Size
430
Surface
Fiberglass
Chlorine
Liquid Chlorine
Thank-you, I had enquired earlier as to thought on the bromine alternative as bromine bank then floater/ periodic shocking process appealed to me.
Some folks, much more knowledgeable than I suggested that as i have 3 kids - 7,9 and 11, that bromine would have difficulty keeping up with the high bather load and that I should stick with the bleach method.

regards
sean
 

Ahhsomeguy

In The Industry
Jul 26, 2016
190
Vero Beach, Florida
Not familiar with what they offer. I do think that you will notice a much more complete plumbing purge or colonoscopy when you use the Ahh-Some brand. I-assure you, it works!
 

Roaddogmm

Member
May 26, 2020
22
Cary, NC
Had the same issue with a brand new tub, def flush with Ahhsome as soon as you can. It made a dramatic difference in my chlorine consumption
 

Enjoying this content?

Support TFP with a donation.

Give Support

Ahhsomeguy

In The Industry
Jul 26, 2016
190
Vero Beach, Florida
Hi seanauld: Please follow the step by step instructions and be sure to wipe the gunk,as you see it collect on the shell. Use a wet towel and don't let this sticky gooey stuff dry on the shell Or it is more difficult to remove.
 

A.O.

Well-known member
Apr 12, 2016
497
Kershaw, South Carolina
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Hi seanauld: Please follow the step by step instructions and be sure to wipe the gunk,as you see it collect on the shell. Use a wet towel and don't let this sticky gooey stuff dry on the shell Or it is more difficult to remove.
So if you wipe down the "sticky gooey stuff" with a towel... is the towel trash then or is it washable? can you put it in the washing machine?
 

Ahhsomeguy

In The Industry
Jul 26, 2016
190
Vero Beach, Florida
A.O. We always recommend an older towel or cloth because you can't tell beforehand just how much released gunk you'll be wiping away. Sure, if you want to keep the towel,for future cleanings you can wash it as normal.