Is combined chlorine immediately after a swim of seven people a concern?

caliskier · Jun 28, 2023

Hi,

We had seven people swim in the pool today, chlorine level is nine, CYA is 60. Combined chlorine level is two (4 drops to clear). Saltwater chlorine generator.

What has me concerned as we have several parties going into the Fourth of July weekend and I went out and tested it and noticed I had combine chlorine. I wondered if this is kind of a normal thing after seven people just went swimming.

Should I react to this or just let the chlorine generator work out overnight for 12 hours which is what it usually does.

Donldson · Jun 28, 2023

Sunscreen and urine are common contaminates that will create CC, so it's common for it to be higher after a few people use the pool. It's often a good idea to bring FC up a few points with liquid chlorine before or after a party to help deal with these, but for this instance if you see them disappear over the next day and your FC is acceptable then there's nothing to worry about.

needsajet · Jun 28, 2023

Try testing again after a few hours with the pump circulating the water and sun on the pool. The CC should be gone by then. It's very likely just the chlorine neutralizing urine, sweat, sunscreen, etc. If it's persisting, then you must have a non-human source of organic contamination. You could do an Overnight Chlorine Loss Test to rule out nascent algae. If people are playing hard, such as watersports or kids really thrashing it, in and out with cannonballs, Marco Polo, etc., you'll have more CC from sweat.

Also be sure to add the R-0871 until the sample is clear, then the one more drop which verifies no further color change. The 5 drops of R-0003 allows for this.

woodyp · Jun 28, 2023

I'd raise FC to SLAM level and circulate over nite. Then see what you have.

caliskier · Jun 28, 2023

Thank you all I will test it again here in about an hour or two and see where were at

revitup · Jun 28, 2023

needsajet said:
Try testing again after a few hours with the pump circulating the water and sun on the pool. The CC should be gone by then. It's very likely just the chlorine neutralizing urine, sweat, sunscreen, etc. If it's persisting, then you must have a non-human source of organic contamination. You could do an Overnight Chlorine Loss Test to rule out nascent algae. If people are playing hard, such as watersports or kids really thrashing it, in and out with cannonballs, Marco Polo, etc., you'll have more CC from sweat.

Also be sure to add the R-0871 until the sample is clear, then the one more drop which verifies no further color change. The 5 drops of R-0003 allows for this.

“Also be sure to add the R-0871 until the sample is clear, then the one more drop which verifies no further color change. The 5 drops of R-0003 allows for this.”
That’s the first time I’ve ever heard this. I always figured an extra drop of R-0871 would affect the accuracy of the R-0003 test for CCs.

needsajet · Jun 29, 2023

TBMK, testing requires another drop until there's no further color change. I recall Dave explaining this to us many years ago, including with regard to the effect on R-0003.