Sample keeps turning pink

[JamesW]

No CYA, but it does contain DMH, which is a similar type of chemical.

1,3-dichloro-5,5-dimethylhydantoin.

1,3-dichloro-5-ethyl-5-methylimidazolidine-2,4-dione

https://www.kingtechnology.com/wp-content/uploads/2023/02/[email protected]

Do a full drain and refill if it is safe to do so.

Note that a full drain can entail some risks for some hot tubs including floating if buried in the ground.

Verify safety before draining.

 

[LBI salt pool]

Hey guys….sorry to keep beating this up. I have a 350 gal tub usually around 100 degrees. I use the color block just to have an idea of FC content and I normally add a couple oz of liquid chlorine in mornings which will boost it 5 ppm at be all set for the day. Heavy loads I add more. Tub went a little sideways recently and I slammed it at 16 ppm and began using the DPD/ fas test after draining 1/2 tub to get CYA level down to 40. No one has been in tub for two days now and it’s covered and out of the sun. This morning my FC was 8.5
I just raised it back to 16.
My main question is this: In a perfect world with perfectly normal hot tub water ( which I’m not sure is achievable) , if no one uses the tub and it doesn’t see sunlight, is there a normal chlorine loss due to the 100 degrees?
Thanks
Steve

 

[Mdragger88]

Everyone’s tub is different. Different sizes, temps, bather loads, ozone or uv presence, age of water/tds.
Your best baseline results to base your average standby fc loss on will be after a fresh purge, drain, & refill.
Understand that the higher the fc the faster the loss so its not linear so 8ppm in 24hrs doesn’t really equate to .33/hr loss if that makes sense.
If you’re crystal clear now with cc 0.5 or less then let fc fall to target range or a little above & also understand that as the tub water ages the standby fc demand will increase.

 

[LBI salt pool]

Thank you! I raised it to 16 again this morning because I had 1 Cc ( yesterday I had 1/2 cc). Water is clear.

 

[phonedave]

At the levels I keep my tub, and at the filtration schedule I run, my tub will loose the equivalent of 2 oz of liquid chlorine a day, that is about 2.5 ppm, if nobody uses it.

However I have an ozone generator - it only runs during filtration, I keep my CYA around 30, and my target FC is 4-5

Different CYA levels, difference FC levels, and different ozone usage will all change your "standby" loss

 

[Mdragger88]

I have never truly calculated my daily standby loss since I have had a swcg the whole time but it went out right before vacation last year so i was manually chlorinating.
I raised fc to my slam level (12ppm) the morning I left & was still in target range (around 5ppm i think) upon my return 6 days later. I don’t have ozone or uv. I also lowered the temp of the tub but it still remained in the high 90’s due to ambient temps.