Super high combined chlorine

[themaccs]

Tested for ammonia today - doesn't appear to be any. I questioned whether or not there was maybe a touch of green to my sample, certainly less than .25ppm, but Hubby said no way, there's no green in there - its just yellow! From what I have been reading, several people have indicated that the pool continues to eat chlorine well after the ammonia is gone. My experience certainly mirrors many of those I have read about, except that I can't seem to get it to end! The pool is unbelievably clear, don't think I've ever really seen it this clear before. I will be out of town Saturday - Wednesday, leaving hubby in charge of the pool - he has agreed to test morning, evening, and bedtime. Readings today were a little better than yesterday, but I still have an occasional CC just over 1.0 (otherwise 0.5 and occasionally just a hint of pink). And FC still seems to be disappearing at around 1ppm/hour - that may be a touch slower than yesterday. We'll see how tonight goes!

[chem geek]

When you were adding chlorine earlier, it probably was combining with ammonia to form monochloramine which is what you were probably smelling and would have had the CC be high. You are now past that point and the ammonia and monochloramine are gone and now you've got other miscellaneous organics that you need to get through -- most likely partially oxidized CYA that won't show up on any test.

You can see from my very brief history of this problem here that I started out with measured ammonia, then CC, and then a slowly dropping chlorine demand with little CC. I caught this conversion process early and mid-stream before it had finished.

Note that if you have any CYA in the water, then that slows down the rate of chlorine getting rid of whatever is left, but protects any FC during the day from breakdown from sunlight.

Richard

[themaccs]

Just thought I would update. We finally stopped losing chlorine overnight when I was out of town a week or so ago- figures I would do all that work so Hubby could have the fun of having the first good reading!! We totaled out at about 125+ gallons of bleach. I am now trying to figure out where to aim for with my CYA level - right now we are at about 55 and losing 5-7 ppm FC per day during the day (0 loss at night). The pool is in direct sunlight for at least 8 hours a day (maybe as much as 10) and for the last week or so we have been up into the 90s every day. I added 2 lbs of Di-chlor earlier this week to get the CYA to where it is now and we put 3 tri-chlor pucks in the chlorinator today to bump it up a little more. I am not wanting to add too much because we are going on vacation in a week and our plan is to bleach it up to a high shock level and fill the chlorinator - so we will be adding CYA while we are gone. We will also have someone check on things every couple of days (we will be gone 10 days). I'm thinking my goal will be about 70-75 for the CYA - I would prefer 60, but we are almost there and still losing a lot to sunlight every day.

Current Readings:
FC - 6.0
CC - 0.2
pH - 7.5
TA - 130
CH - 260
CYA - 55

[aylad]

Hi, and thanks for the update--we like to hear the end result after helping people with their pools--we all learn from it!!

I don't remember where you live, but losing 5-7 ppm chlorine daily is an awful lot. I'm in northwest Louisiana where the air temps are in the high 90s (heat index in the 105 range due to the 97%+ humidity), and my pool is in full sun from daylight to dusk--and losing 4-5 on a very hot day with a big bather load of kids is still a lot for me. I intentionally run my CYA at 80-90 ppm for that reason--with my weather conditions, I found that I lose much, much less FC during the day with it that high than with it lower. I'm one of the few that does this, but in my climate it's necessary. I lose 2-4 ppm on a hot day with a pool full of kids all day, and 94 degree water.

It's really a decision you have to make, because if you raise it to the higher levels and it doesn't work out for you, then you need to drain/refill to lower it...but then again if you're in a similar climate to mine, you might find that you don't lose nearly as much chlorine to the sun.

If you've got trichlor in the pool now, and use the chlorinator while you're on vacation, you're going to end up at around CYA of 70 anyway, so try it at 65-70, keep track of how much you're losing, and if it's less than you're losing now, you might want to consider going a little higher. Just keep in mind two things: 1) with the trichlor, you need to keep a good eye on your pH because trichlor will drive it down, and 2) the higher CYA works well in my pool because it's open year round--remember what the CYA breakdown did to your pool in terms of CC when you opened this year, and consider that in your decision. Might be worth it to raise CYA during the summer but drain/refill before closing it for winter, or at least set it up so you can keep chlorine in it during wintertime to avoid the ammonia problem again.

Janet

[themaccs]

Janet,
All those things you mention are concerns I am trying to balance. I'm not sure I understand why I am losing so much chlorine during the day. I retested my night time loss again last night to be sure we aren't losing any at night - we put a jug of bleach in at around 9:30 to bring FC up to 8ppm, shut off the chlorinator (which we had put 3 pucks in earlier in the day and set it on low to try to bump up CYA to slow daytime chlorine loss), and tested at 11:00. FC was at 8.0, CC - 0.5. Tested this morning before the sun hit the pool (about 7 am) and it was still 8.0, CC - 0.5. We do get a lot of direct sun-light on the pool. We are in south central Kansas. The pool is a direct Southern exposure with the direct sunlight first hitting east end of the pool by about 8 - 8:15 am and the first shade hitting the west end of the pool at about 6 pm. That's nearly 10 hours of strong direct sunlight, and the last week or so has been in the 90's nearly every day, dry, and nearly cloudless. I have been assuming that has accounted for my continued high chlorine loss during the day despite stable FC levels overnight. I just ran another test ( it is now about 1 pm - so 6 hours after my last test) with the following results:

FC - 5.5
CC - tr
pH - 7.4
TA - 120
CYA - 50 ( I really have trouble reading that dot - but 3 different tests got the same result) (we did have to add quite a bit of water today due to evaporative loss - level was down to bottom of skimmers)

Pool is 19500 gallons "sport" pool - 18x36xaverage 4 foot depth (3 foot shallow end, 5 foot middle, 4 foot other end).

The other issue that puzzles me a bit is my continued tr-0.5 ppm CC - we have had it at shock level 2x since we stopped losing chlorine at night, water has been crystal clear for weeks now, but CC doesn't seem to change: usually just a trace during the day, 0.5 first thing in the morning.

Any thoughts out there?

Thanks again for being here.

[aylad]

I can't explain why the higher CYA works better for me, but it does. If I kept my CYA at 50, I'd be pouring stuff in the pool constantly, trying to keep it clean. The best I can suggest is that you up the CYa by 10 ppm, and see if that does anything to lower your chlorine loss. If so, then up it a little at a time until you get to the lowest level of CYA that will keep the chlorine in the pool.

The trace of CC you're seeing is probably just pollen or other airborne "stuff" that the chlorine is burning off--once the sun hits the pool, it will take care of the CC if it stays that low. Sweat, suncscreen, etc can contribute to it, too. That's why we wait until CC gets to 1 or higher before we recommend shocking the pool. As long as it's not staying above 0.5, and you are not losing chlorine overnight, then your usual chlorination will take care of it.

Janet