Chlorine demand

[ivyleager]

Is there a general time frame when water holds chlorine after ascorbic acid treatment? Also, my pH is continually rising. (assuming d/t all the bleach I'm adding).

I'm going on 3 weeks post treatment and I STILL have bleach being consumed very quickly in my pool. I generally add bleach every other day. Today I added in the morning and evening.

This mornings numbers at 8:30am: (I added 1.5 lg jugs of bleach around noon day before- raised 5-6 ppm).
Water is crystal clear.
FC 0
CC 0
TC 0
CYA 50
TA 80
pH 7.6 (hardly moved after adding 4 c. muriatic acid - Home Depot brand, not very concentrated I think).
CH 130

To prevent algae, I'm running pump/filter 24/7 and used whole bottle of polyquat before AA tx, and am adding about 10 cc a week now. So far, so good.

Just suprised that chlorine isn't holding.

 

[chem geek]

It's not a timeframe, but rather an amount of added chlorine. One pound of ascorbic acid is equivalent to 100 fluid ounces of 6% bleach or 4.8 ppm FC in 10,000 gallons. If the ascorbic acid didn't get used up very much reducing metal stains (and it usually won't), then the rest will use up chlorine. Some of that chlorine is what you started out with when adding the ascorbic acid and much of the excess will consume chlorine that gets subsequently added. So if you know how much ascorbic acid you added and know the FC level when you started, you can calculate the worst-case amount of FC you'll need to add to have it start to register again. That assumes that algae growth hasn't started.

 

[ivyleager]

No algae growth at all. I'm running filter 24/7, using Aquabot 5 hr/day to keep things clean, and making sure to add polyquat weekly. I'm making sure I have 4ppm chlorine in water as much as possible, testing 2x/day. Don't want to end up needing to superchlorinate yet, per mbars guidelines.

I used 2# of AA for my 23K pool. Chlorine was zero when dumped it in. I've used 5# of Cal-hypo and 12 lg. jugs of bleach so far. So based on your calcs above, I should be more than done. Here's hoping!

 

[JasonLion]

You always need more than the calculated amount due to additional chlorine getting used up breaking down organics and lost to sunlight.