Clear, but no chlorine???

[BigDave]

@CarlD:mary jo's pool has CYA of about 150ppm, CH of 750, a history of trichlor use, periods of zero measurable chlorine, and low pH. There's no visible algae, and high chlorine demand. The Nature 2 cartridge is in place but hasn't been replaced in the last two years. There is a possibility that some amount of fertilizer made it into the pool. My guesses are that some CYA may have been converted to ammonia causing chlorine demand (no bad smell so probably not); the fertilizer may be causing chlorine demand directly; or that a nascent algae bloom (possibly aided by fertilizer) is causing chlorine demand.

@mary jo:CarlD is right, three times during the day should be OK but I don't think you need to vac to waste since you can't see any algae.
Do you have CC readings for the FC tests last night and today?
I'd like to see the FC stay above 30 but we run the risk of bleaching the liner.
Please continue to measure FC and CC after the last dose in the eveing has had a chance to mix in and after the sun is down and again before the sun is on the pool and before adding more bleach.

[mary jo]

yes, last night (11:00pm) FC=33
this morning (7:30am) FC=22
I added 2 1/2 jugs of bleach.
will test again @ 12:30pm

[FormerBromineUser]

Any CC?

Great minds.....

[BigDave]

How about Combined Chlorine?

Thanks FormerBromineUser!

[mary jo]

The test sample was barely pink (after adding the 5 reagent drops), then one drop of R-0781 turned it water clear, so <= 0.5

[mary jo]

Just had another thought : it looks like rain here. Should I cover the pool if we do get rain? I've never had rain water in my pool before ( another big rule from the pool installers which I've always adhered to- always cover the pool when it rains.... Rainwater is bad).

[JimK]

Just had another thought : it looks like rain here. Should I cover the pool if we do get rain? I've never had rain water in my pool before ( another big rule from the pool installers which I've always adhered to- always cover the pool when it rains.... Rainwater is bad).

I don't know there's anything inherently bad about rainwater. I've never noticed any negative effect. The only time it's an issue is if we get too much and I have to pump water out of the pool (may have to rebalance after that). Of course if we get a lot of wind as well then there the mess to clean up from all the crap from the trees (we have a lot of trees around).

[mary jo]

Oh- I see. At night, dose the pool with bleach to get a FC of 30, wait an hour and THEN take another reading for the night. Sorry, my brain is slow.

[FormerBromineUser]

Yes! You need to make sure you've reached the target FC. Under shock conditions you don't want to make assumptions. (Once your demand is gone, you won't have to do this).

Have you checked your CYA lately? BigDave mentioned the possibility of some conversion of CYA and I don't have time to back track to see when you last checked it.

[mary jo]

Last week (august 11) my CYA tested at 150. I typically do the test 3 times and average. (since it's a more subjective test than most- i think). I have not added any hose water since last week, but I will test it again today.