Trichlor While Away

[GrisGrisGumboYaYa]

First time caller here. Two weeks ago, I had my pool re-plastered, and I still have another two weeks before I can add salt and run the SWG. I’ve been maintaining my FC with liquid chlorine to date, but I have to travel next week for 5 days, and have no one I can expect to dependably check/adjust my chemistry while I’m gone.

I should add also that I have a spa with a spillover to the pool when the pump is running (24/7 for another couple of weeks), so I’m losing ~3-4 ppm of chlorine a day with all the aeration.

I figure my best bet is to add a few tabs of Trichlor to a floater the day I leave. I can afford the increase in CYA, and the acid might help keep down the creeping pH from the new plaster. Is my logic sound here? If so, any suggestions on many tablets should I add?

TIA!

FC - 5
TC - 5
pH - 7.5
TA - 80
CYA - 40
CH - 350

 

[Texas Splash]

Sounds like a good plan. You can also add some liquid closing on your departure day as well up to slam level.

 

[DrewLG]

I’m losing ~3-4 ppm of chlorine a day .... any suggestions on many tablets should I add?

So here's how I do that calculation:

In PoolMath "Effects of Adding", I see that one 8-ounce Trichlor tablet raises FC in my small pool by around 7 ppm, and I know from experience that a tablet in a floater in my pool takes 10 days to dissolve. So on average, a single tablet raises my FC 0.7 ppm per day.

If I were losing an average of 3.5 ppm per day, I'd need 3.5 / 0.7 = 5 tablets to counter the loss.

Of course, it's not quite that simple -- the tablets don't raise FC linearly, the FC loss isn't linear, multiple tablets stacked in a floater tend to weld together and dissolve more slowly than tablets whose entire surface area is exposed, etc. -- so to paper over those errors, I second @Texas Splash's recommendation to also raise FC with liquid chlorine before you leave. If the CYA number you posted is correct, SLAM level for you is 16 ppm, so you can raise FC to any level up to that concentration.

When you return, your pool will be safe to swim in if FC is anywhere between your minimum level of 3 ppm and your SLAM level of 16 ppm.

 

[GrisGrisGumboYaYa]

Seems like sound advice. Thanks to you both for the replies.