Trichlor and the sun

Pcmaker

Well-known member
Jun 7, 2012
70
Las Vegas, NV
This is a commercial pool and we use trichlor. 40k gallons.

The pool doesn't get any sunlight during winter. How crucial is UV to trichlor? Pool turns green many times during the cold season even when tje free chlorine is usually at around 5-7 ppm with CYA at 30-40, pH at around 7.6-7.8 and TA at around 110. Pump runs 24/7 and is a heated pool. Around 120 GPM flow rate.

In order to combat this, I added 10 oz of phosphate remover every week and that helped a lot.

I'm thinking of using liquid chlorine this winter to try and see if it works better.

We're also thinking of switching over to cal hypo feeders as we have ORP controllers tied to our trichlor feeders and it doesn't work too well due to CYA.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,646
Northern NJ
What bather load does the pool get? TFP FC/CYA Chart recommendations are for residential pols with low bather loads.

Cold season doesn't matter when water is heated.

UV only affects CC burnoff in water. Not trichlor chemistry or effectiveness.

While you say "free chlorine is usually at around 5-7 ppm" I suspect it may be dropping lower then minimum at times due to high bather load.

You need to clear the algae that is lurking in the water. In residential pools we use the SLAM Process. Once you have algae free water you need to run a higher FC level, if your regulations allow.
 

Pcmaker

Well-known member
Jun 7, 2012
70
Las Vegas, NV
Very small bather load during the winter. People go out to the pool to tan. If there's no sun hitting the deck, nobody goes out there. Maybe 5 bathers a day at the most during winter.
 

Pcmaker

Well-known member
Jun 7, 2012
70
Las Vegas, NV
We use rainbow chlorinators with solenoid valves hooked up to ORP controllers. We backwash out a lot of water every day to keep CYA at around 30 to 40. The FC is pretty constant as well as CYA. When pH gets to 7.8, we add a gallon of acid. Usually brings it down to 7.4. TA pretty much hovers at 100 to 110 all the time.
 

BowserB

Silver Supporter
Jul 29, 2018
120
Katy, Texas
In order to combat this, I added 10 oz of phosphate remover every week and that helped a lot.
Pcmaker, this is interesting. I'll be curious to hear some of the long time experts here and their opinions on this. That is, is it really working, is it PCmaker's imagination, or is there something about commercial pools that makes them different.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,646
Northern NJ
Pcmaker, this is interesting. I'll be curious to hear some of the long time experts here and their opinions on this. That is, is it really working, is it PCmaker's imagination, or is there something about commercial pools that makes them different.
Phosphate removers remove algae food. They do not get rid of algae you have in the water. With TFPC methods our goal is to never have algae in the water so you don't have to worry about phosphates. They may slow down algae growth. To clear water of algae it takes chlorine and the SLAM Process.

 

Pcmaker

Well-known member
Jun 7, 2012
70
Las Vegas, NV
Adding phosphate remover weekly was the only thing that worked. I tried having FC at just under 10 constantly while keeping CYA at 30 maximum. That didn't work.

The only thing different between summer and winter is no sun hittting the pool and having almost zero bathers.
 

Pcmaker

Well-known member
Jun 7, 2012
70
Las Vegas, NV
And it will not work because SLAM FC for CYA 30 is at least 12. See FC/CYA Chart
Can't go over 10ppm on FC as this is a public pool that's overseen by the local health dept. Max FC allowed for public pools is 10ppm before they shut you down and fine the hotel.

How are you testing your water?
I use a Palintest photometer, the same one the health dept. inspector uses when he shows up for his random pool inspections.

I wonder if UV as a secondary disinfectant would help as there's no sun to help FC break down CC during the cold season.
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
370
Spring Valley, NY
I say do a water exchange to bring your CYA down to zero then slam may be under the limit for FC for the health department. I'm not sure what the other health department criterias are or aren't for a public pool.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
9,646
Northern NJ
I say do a water exchange to bring your CYA down to zero then slam may be under the limit for FC for the health department. I'm not sure what the other health department criterias are or aren't for a public pool.
Doesn't have to be CYA 0. SLAM FC for CYA 20 is 10. CYA 20 is about the lowest you can measure and it still protects the water. The winter is a good time to do it when suns UV is less.
 
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Reactions: wireform
Aug 31, 2019
10
WA
I used to be in charge of a public pool many moons ago (Like 25 years ago). It may be different for you, but I always had the option of closing the pool, and then I could do whatever I wanted with the chemistry. Perhaps the Boss wants the pool open, I don't presume to know, BUT, could you close the pool to the public, and do a proper slam for a few days, and then reopen it? (explain to your boss what you are trying to do and he may be supportive)