Chlorine consumption seems to be double this year. Why?

[joninnj]

Thanks for all the tips. The thing with more accurate measurements and solar covers is that I didn't have any problems last year, are not doing anything different this year, and chlorine consumption is double from last year. The antifreeze issue might have contributed, but it's been over a month and seemingly not getting any better.

One thought. I wonder if there is something off with the new FAS/DPD reagent. Specifically, I wonder if the drops coming out of the R-0871 bottle are larger than they should be, incorrectly depressing my FC readings. I say this because the K-1000 tests seem yellower than the drop test readings (I know, it's off the scale in any case), and the water in the tube also seems pinker than the drop test readings. Is this possible? Again this is in the context of a perfectly clear pool with a CC never higher than 0.5.

Can't hurt to get more reagent. I'll give it a try.

 

[joninnj]

I give up

I give up. To summarize, my pool is consuming double the chlorine from last year. Things that have been ruled out:
1. Chlorine potency: using the same stuff all this year that I used all last year (Walmart 8% bleach), reasonable fresh stuff by manufacture dates, etc. No change from last year.
2. Chlorine administration: timing of testing and adding bleach unchanged from last year.
3. Testing quality: I am still not 100% convinced of this, but the facts (new reagents for this season, ordered additional new reagents with the same results). I am suspicious because, for example, tonight I got a FC of 3.5, but the Taylor test seemed to be 5+. Regardless, the facts suggest this is not the issue.
4. Organics consuming more chlorine: I have passed two OCLTs, and the CC has never been over 0.5. No unusual high use of the pool, no significantly greater number of diapered babies in the pool. No signs that organics are consuming twice as much chlorine as last year.
5. Filtration: water is perfectly clear, my robot routine is unchanged. While the pump was replaced (with the same model) this year, I don't thing this is a filtration thing.
6. No changes in the pool layout, shade, cover (never used), etc.

One outstanding possibility:
1. Antifreeze. This was suggested earlier. The antifreeze smell is long gone, and I just don't see other reports of antifreeze doing this for months. I suppose this still could be an issue, but I would think this was a real "thing," it would be discussed more frequently here.

So I give up. It's 2 gallons of bleach a day now. This may well drive me to a salt water generator next season. 2 gallons of bleach each day is a lot to buy and lug...

 

[gregsfc]

I would think if it is a bad FAS-DPD reading, and your adding double the necessary bleach each day, then you'd start getting orange colored OTO test results pdq. Walmart 8.25 has been exactly as expected for me this year.

 

[Catanzaro]

Joninnj:

Let's take a step back. 2 gallons of 8.25% in a 30,000 gallon pool is raising your FC by 5.7 and salt by 9.3. What does not make sense is that you passed the overnight test (less than 1 ppm loss in an 8 hour period (could be longer) with no sun). What I would do, if this was my pool is add 2 gallons at 5 a.m. in the morning after testing at 9 p.m. the night before. Confirm again that you lost less than 1 ppm and you passed the OCLT. Then every 3 to 4 hours (depending on preference) test. I would use .5 ml to save on reagents and multiply by 1. Track the conditions outside. Are there a lot of trees. What about people cutting grass. High winds blowing stuff around in the pool.

My friend called me yesterday. He uses the TF-100 kit, but not a member. The water is so clear (was so clear) with 1 MD, 1 Skimmer and 1 return in shallow end. Brushes 2X weekly. Always keeps FC at 7.5 of CYA. His water became cloudy. I suspect that the grass clippings and fertilizer that entered the pool caused this issue. Yes, it has been hot, although he is putting in 1/2 gallon daily in a 20,000 gallon pool. I use 32 oz. one day and 64 oz. the next day in a 15,000 gallon pool with no issues. It is possible the Fc slipped and has a little algae. I am not there, so can not tell the water quality.

Moral of the story. Something is causing the chlorine consumption and I doubt very highly it is your testing. Is it at all possible your CYA is too low. Some pools act funny. Maybe increasing CYA to 50 would be a start. Some external conditions are causing this problem.

Something else you could try. If you have a tarp, not a heavy mesh cover, why not put it over the pool for 2 days (out of the sun) with the filter running and perform a few tests. If you are still loosing 5.7 ppm daily, then personally I would give up myself if all your levels were perfect. And remember, the higher the levels, the faster you will burn off as chlorine consumption is based on a % and not a flat ppm daily. This is the reason why I always suggest performing the overnight with levels under 10. One last thought, what about PH. The higher the PH, the more consumption of chlorine. Chem-Geek has an great article somewhere which I could locate. What is your PH? Maybe lowering the PH to 7.2 to see chlorine consumption is another step you can take.

I would lower PH to 7.2, add chlorine add night, test one hour later and cover the pool. Go 24 hours and test again to see where your levels are. Please keep us posted.

 

[Catanzaro]

One thought. I wonder if there is something off with the new FAS/DPD reagent. Specifically, I wonder if the drops coming out of the R-0871 bottle are larger than they should be, incorrectly depressing my FC readings. I say this because the K-1000 tests seem yellower than the drop test readings (I know, it's off the scale in any case), and the water in the tube also seems pinker than the drop test readings. Is this possible? Again this is in the context of a perfectly clear pool with a CC never higher than 0.5

The K-1000 seems to me, at least to be .5 to 1 ppm higher than the FAS/DPD test. Although, I always confirm weekly with the extended test. 1 ppm variation, would still put you at 4.7 ppm loss daily. In addition, testing error is maybe 10% at most. You are still at 4 ppm., which is very possible. Given other variables, which include hot weather, lower CYA and higher PH, you clearly could have found your problem. I use the pool calculator, add accordingly and double up if the pool has a lot of activity. If the K-1000 shows very little chlorine, I add during the evening and run the filter for 2 hours. The pool has never given me any problems. Maybe too much emphasis on testing. Add 3 ppm daily based on pool volume and do not test. Do this daily and test every 2-3 days to see if any algae surfaces or the condition of the water. Then perform the math calculations, which include starting point, additions, ending point and how much lost over 3 days, etc.

 

[joninnj]

Catanzaro, thanks for all the thoughts and tips. I will try the OCLT as you suggest and also try raising CYA back up to 50. Through multiple drains (splash out, closing) and fills (rain mostly), CYA has dropped to 30 now. Hopefully, getting it back to 50 will slow down loss. Regardless, I am seriously considering a SWG for next season.

 

[Catanzaro]

The SWG is an option to save you time. Although, the up front cost takes years to break even. My SWG is running $1,500 installed. The salt (maybe $100-$200) as I am not sure yet. Depending on the cell and ongoing salt requirement, it could take 7 years to break even. It only runs $200-$235 per season in liquid chlorine. Try some of the suggestions I offered as you can not be loosing l ppm overnight (8 hours) and 5X the amount during daytime hours.

 

[joninnj]

TO revive my own thread from last summer, revisiting a suggestion from Catanzaro and looking at my logs from the last 2 summers, could the difference in chlorine consumption be all driven by CYA levels? Two summers ago, CYA ran in the 60-80 range, and the pool took a gallon of bleach a day. Last summer, I dropped CYA down to 30-40, and it consumed 2 gallons of bleach a day. Is the answer as simple as CYA?

BTW, I am getting a SWG installed...

 

[NUTNDUN]

TO revive my own thread from last summer, revisiting a suggestion from Catanzaro and looking at my logs from the last 2 summers, could the difference in chlorine consumption be all driven by CYA levels? Two summers ago, CYA ran in the 60-80 range, and the pool took a gallon of bleach a day. Last summer, I dropped CYA down to 30-40, and it consumed 2 gallons of bleach a day. Is the answer as simple as CYA?

BTW, I am getting a SWG installed...

CYA could definitely be the main culprit. That is a big difference between your CYA levels. I have noticed a big difference in FC loss during the day just being down to 60 from our normal 80. We have had a ton of rain and I am working on raising it back up.