Chlorine in spa

moreira85

Well-known member
Nov 8, 2015
168
Boston, MA
I noticed when I add chlorine to my hot tub 400gal the chlorine drops pretty fast and doesn’t hold. Do the same rules apply to a spa as a pool regarding SLAM? And should the hot tub hold chlorine for the day?
ph 7.5
TA 80
CYA 30
Calcium 180
FC 0. I added 1.5oz of chlorine this morning.
 

RDspaguy

In The Industry
Mar 21, 2020
1,387
Cabool, Mo
Ozone will deplete chlorine, that's why I like it. It allows me to shock heavily after use to destroy contaminants and not have to soak in a chemical bath the next day. I typically have less than 1ppm when I use it, even after raising it over 5ppm the day before.
It is always a good idea to purge with Ahh-Some on any new spa. They often sit in storage and shipping with water in the pipes from testing at the factory and can grow all kinds of nasties inside the pipes that chlorine can't get rid of.
 
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RDspaguy

In The Industry
Mar 21, 2020
1,387
Cabool, Mo
I'll bet you have a CD (corona discharge) ozonator on a 24/7 circulation system.. And no cc at all. Makes life easy. I won't own a spa without one for my personal use, and I have owned many, as I have been refurbishing used tubs for 2 decades.
I just hope you are using liquid (bleach) and not dichlor granules or your cya will be off the chart in no time.
 

moreira85

Well-known member
Nov 8, 2015
168
Boston, MA
Wow this spa is really not going well. I’ve had it about 10 days. All levels look good but won’t hold any chlorine. I added a bromine dispenser as well. I added 8 ounces of chlorine and FC was 12 ppm at 1pm today. I just checked it 4 hours later at 5 ppm and virtually all FC gone. I added the chlorine because when I uncovered the spa water this morning it was very cloudy.
 

RDspaguy

In The Industry
Mar 21, 2020
1,387
Cabool, Mo
FC is gone, but what about CC? Ozone will deplete FC as well, but that does seem excessive. I suspect you have a biofilm issue and should purge with Ahh-Some spa purge.
 

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