Is 5ppm per day normal CL loss?

[lovingHDTV]

My pool gets lots and lots of sun. I've noticed that for the last 3 weeks or so, since I changed over to BBB that I average 5ppm CL loss per day. This turns out to be about 1 bottle (174oz) or 6% bleach per day.

I put in the bleach at night, measure in the AM, and there is no drop. However, when I measure in the evening it has dropped from 7pmm to 2ppm. My CYA is 80-100ppm depending on my testing vs pool store (80ppm me, 100ppm store).

Just wondering if this sounds OK? It drops even more if my kids use it. I'll go from 7ppm -> 0ppm if they use the pool.

thanks

 

[JohnT]

That sounds a little high with CYA that high, but the fact that it doesn't drop overnight sure points to the sun being the culprit.

 

[chem geek]

5 ppm in 15,500 gallons is actually 160 ounces (1.25 gallons) of 6% bleach (since it's really 6.17% Trade -- i.e. by volume). And yes, that's a rather large chlorine loss given the high CYA level. When you say that you noticed this only when you switched to BBB, what was your chlorine source previously (Trichlor, Cal-Hypo, etc.) and did you keep track of how much you used per week before during previous years' hot seasons?

Also, what are the depth dimensions of your pool -- shallow end and deep end? Finally, how are you adding the chlorine to the pool -- at what location (over a return, into the skimmer, walking around the pool, etc.) and how quickly and how close to the pool surface do you pour?

Richard

 

[duraleigh]

HD,

That's too much loss. Full sun pools typically experience around 2ppm daily.

It sounds like you've got some contaminants in the pool and need to shock. Up to at least 25ppm with that high CYA and hold it there. I'd put it in at night, test in the morning and readd as necessary to bring it back up to 25ppm.

 

[lovingHDTV]

I kinda thought it was too high also.

The pool volume is off the PB design plans so maybe it is a little off? It is a kidney shaped design with the shallow end at 3ft, middle 5ft, and other end 4ft. I never wanted to try and calculate the volume so I've always gone with what the PB has on the drawings.

I put the chlorine in at night in the skimmer with the pump turned on. I never tracked chlorine usuage before all I know is that I have always had to fight algae.

I do get a lot of organic matter in the pool, I have the kids scoop out leaves everything morning and I do the same thing at when adding the chlorine. I was thinking that it may be the leave and stuff that cause the issues, but I really don't see change overnight. I'll monitor more closely, for a little while longer, but at 1 jug a day I'm around ~$70 per month in bleach. That is close to what I spent on tri-chlor if I remember correctly. However, on top of that I was using $30 in algecides along with the tri-chlor.

I'll shock to 25ppm tonight and see how that goes. I hardly have any measurable CC so I did not think I needed to shock, but I'll do it tonight. Maybe I'll use up some of my cal-hypo that I don't use anymore to get rid of it.

thanks for the feedback as I had no idea what to expect. I'll keep working on it,
dave

 

[chem geek]

Well, dave (duraleigh) may be right about you having a nascent algae growth problem since the 7 ppm FC is a minimum at 100 ppm CYA to prevent algae so letting it go down to 2 ppm FC is most definitely taking a risk. It is strange that the chlorine holds overnight, but just keep in mind that even if you shock to kill any algae and get your pool to hold chlorine better, you will still need to be at 7 ppm for your lowest point so that probably means adding chlorine to get to at least 10 ppm FC if not 12 ppm FC so that you don't go below 7 ppm by the end of the day (or the next time you add chlorine). It will then be interesting to see if your chlorine loss is 2-3 ppm FC (from 10 to 8 or 7) or 5 ppm FC (from 12 to 7).

The reason I asked about your pool's depth is that we are modifying our theory about how CYA protects chlorine since a few users have reported and shown by experiment that high CYA levels have chlorine last longer than would be predicted on the basis of CYA's affect on disinfecting chlorine alone. The thought is that CYA provides additional "shielding" through direct absorption of the sun's UV rays, but this effect would be stronger at greater depths. The pools that show this effect most strongly indeed have pool depths of 6 to 8 feet in the deep end. So your pool depth of 3-5 feet instead of 3-6 or 3-8 may mean that your pool isn't a good candidate for higher CYA levels protecting chlorine better even after keeping the FC levels correspondingly higher to protect algae. It may mean that for your pool, having 50 ppm CYA with 3.6 ppm FC minimum or 30 ppm CYA with 2.2 ppm FC minimum may work better at using less chlorine overall. It's too bad that it is so hard to lower the CYA level (i.e. through dilution).

The reason I asked how you introduced the chlorine is that if it wasn't getting well mixed quickly or was exposed directly to the sun even briefly, it will decompose rather quickly. That does not appear to the be case in your situation. Measuring your chlorine level 30 minutes after addition and comparing to what you expected would confirm that the loss isn't during chlorine addition.

Anyway, try the shocking first just in case this is nascent algae and then maintain the 7 ppm FC minimum so target a higher level during addition (i.e. 10 or 12 ppm) and then see what the loss is. We can then go from there.

Richard

 

[lovingHDTV]

I just added 64oz of 73% cal hypo, that should have brought my FC from 2.0 - 24.39ppm. I put it in the skimmer with the pump running. 45min later I tested and got 27 drops so that makes 13.5ppm. That kind of rise would be for a 30,000 pool, but mine is not that big.

I'll wait and test again in 30min. to see if it is still rising.

dave

 

[lovingHDTV]

I'm at a loss here. Hoping someone can give some advice

I've been watching my FC closely to see what is happening.

After waiting 45min last night (see previous) my FC was 13.5ppm. I waited an additional 20min, then tested again and got 16ppm. So I went to bed.

In the AM I tested and it was 13ppm FC, not sure what the peak was. I then added 2 lbs of 73% cal hypo as that should have brought it back to ~25ppm and went to work.

I just got back and measured 13ppm FC again. This time I back washed, even though the pressure was not high, and added 3 lbs of cal hypo, which should bring it to ~29ppm FC. I'll measure in 1.5 hours and see what I achieve.

I guess I'm at a loss because my water has never been so clear, where is all the FC going?

CC 0
CYA 80-100,
TA 90
CH 670
borates at 45ppm,

thanks,

 

[duraleigh]

HD,

Well, I'm pretty sure chlorine disappears from a pool for one of two reasons....the sun or organics in your pool. Sounds like you've pretty much eliminated the Sun as a contender so organics seems to be the only choice.

I didn't do my homework and reread the whole thread so I don't know how long you've been trying to maintain breakpoint but it sure sounds like you need to keep pouring in the Clorox....you're killing something and when it's all gone, your chlorine consumption will decrease dramatically.

 

[pooladdict]

Is it possible something is getting in the pool during the day...polen etc..and the chlorine is being reduced to eat destroy this?

Rik

 

[duraleigh]

Is it possible something is getting in the pool during the day...polen etc..and the chlorine is being reduced to eat destroy this?

Rik

Yeah, Rik, that's a good thought but I'm not confident pollen or other airborne contaminants could account for that much chlorine loss. My bet would still be on the "bugs" in the water.

 

[lovingHDTV]

I used cal hypo cause I have a bunch to get rid of, however I"m almost out

I brushed the pool today and did notice white powerdery stuff on the floor, I'm not sure if it is dead algae or undesolved cal hypo. As I can't see anything in the water, I doubt it is algae or does algae get visible when it is dead?

I also got two large (size of large pizza) black stains now, one on the seat in my spa and one on the floor of my pool. I've never seen these before and only saw them when the FC got in the 20's. I'm hoping they go away when the FC goes back down.

Anyone ever hear of something like this?