Chlorine Usage?

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gsheltonlhc

gsheltonlhc

0
Nov 3, 2012
15
Lake Havasu City, AZ
Let's get this out of the way 1st. FC 6, CC 6, TA 100, CH 500, CYA <30? (added 132 oz Bleach tonight just like every other night). It is a 17,000 gallon, gunite pool, in direct sun all day, and my primary source of chlorination is 8% bleach. We live in an extreme climate and summers are very hot with the summer months (June-Sept) well over 100 degrees and often over 115, with lots of sunshine.

I would really like to lose my "test dummy" avatar :hammer: and thought I was doing pretty well, until today. I bought this house (and pool) September of last year. After having pool issues in Northern CA, before moving here, I found your site and think I have learned a lot. Our pool surface was really stained (Blue), tested at 7500 ppm TDS, smelled bad, tasted bad, and had scaling issues. In December of Last year I drained the pool, acid washed it and refilled with our city water. I did not address the scaling issue at that point. My pool looks, feels, smells, and tastes great. The only issue is I have is it seem to use a lot of Bleach, on avg. 130 oz of 8% every other day.

I know the CH is high but it's not easily solved as the tap water from the city tests at 350 ppm. I went from 350 to 500 in 6 months. I have not added anything to my water except bleach, and muriatic acid. My water is not cloudy and pump circulation appears fine. The Cyanuric Acid level is baffling though. By March I had added enough Trichlor to bring my ppm to 50. I had Leslie test it and they came up with 45 ppm so I thought that was close enough for comparison. I continued to add trichlor until May when I should be at 80 ppm, according to the pool calculator.

I had read at your site that splash out was the only way to really drop CYA levels and we don't have a lot of that. Evaporation though should be considerable. We have an auto fill device so I don’t know how exactly how much there is. I searched for Cyanuric Acid Degradation and found this at your site:The primary step is the cleavage of the triazine ring and it is proposed by Wojtowicz that this primarily involves a fully chlorinated isocyanurate species Cl2CY. What? I do enjoy reading the info you have on chemistry and actually understand some of it but, WHAT?

Any thoughts? All help would be appreciated.

Thanks,

Greg
 
Can you tell us what you are using to test with?

JohnN brings up a good point. Please validate whether you meant to say that TC = 6 or CC = 6. I wrote up my response about going through the shock process based on the CC=6 that you posted. If you meant to say that TC=6 along with your FC=6, then no shock process is needed.

A CYA of <30 ppm and a CC of 6 ppm are the two main reasons you are going through so much bleach. The low CYA offers the chlorine little protection from the sun and the high CC indicates some sort of organic contamination. You need to go through The Shock Process. Before starting, I would get CYA in the 30-40 ppm range and lower pH down to 7.2 (BTW, I did not see pH in your test results). Do not test pH once you begin the shock process until your FC drops below 10 ppm. Once you are done with the shock process, I would maintain CYA in the 50-60 range for your location. BTW, the lower CYA level proposed for going through the shock process will allow you to use a bit less bleach.

CYA loss on the order of what you have experienced is quite rare, although not unprecedented, in very sunny and hot areas like Arizona where you live. There is some speculation that intense sunlight may act as a catalyst for CYA breakdown.

The other situations that can result in a rapid loss of CYA are (1) Degradation by bacteria, (2) CYA test results can be off when the water is very cold, and (3) The CYA level seems to test differently when the pump has not been on in a long time. I think we can rule out items 1 and 2 in your case as they are rare, but more common in pools that are closed for the winter. Item 3 might be a possibility. All tests should be performed with the pump running for at least 15-20 minutes.

Splash out and refilling will lower CYA, but by no means rapidly.

The bottom line is there are still a few things about CYA that we do not know yet. The best defense is regular testing and adding more as needed.

As for the high CH, there's not much you can do about the CH level of your city fill water. High CH can be managed by keeping pH in the lower end of the recommended range. But before delving too deeply into this, let's first work on determining what your FC, CC, and TC really are as well as figure out what's going on with the CYA.
 
I'm a noob, so don't take any of this seriously. I'm completely making up theories on stuff I'm unqualified to speak on.
That being said, this is the internet, so this isn't unusual. :blah:
My first question is why are you pouring in so much chlorine? If you aren't seeing algae or other issues, I don't think you would need to keep 6ppm+ all the time. I'd think 1ppm or so should more than do the trick given how little pollen, humidity, and general organic stuff I'd imagine you have.

That decomposition post was interesting. It said that the decomposition reaction was highly dependent on temperature, pH, and FC levels. It went up with all 3 of those, and could easily be over 1 ppm/day if those things were high. What is your pH? If you are running a pH of like 9, then you need to lower it for several reasons, only one of which is CYA decomposition. Given your low humidity, I'd guess your pool is pretty cool unless you keep a solar blanket or heater on (dew point today ranged from 14F to 27F per wunderground.com). If you are keeping it hot, you could be losing CYA to the described decomposition mechanism, particularly given your high FC levels.

All that nonsense aside, I bet that decomposition isn't the reason you're losing CYA. I base that solely on the fact that I don't notice lots of posts about CYA decomposition being a problem (terrible logic, I know). In my imagination, the much more likely scenario is that you have a leak. Somewhere in your piping, your plaster, or whatever, you're slowly losing water. You don't really notice it since 1: you automatically make up water. 2: your high evaporation climate means you'd be adding a bunch anyway and 3: your high evaporation climate means you won't easily notice some water leaking because the poor dry desert sand just inhales it. Is there a place around your pool, your filter, or in between where either stuff is greener (because of the water) or stuff is less likely to grow (because of the chlorine)?

Someone who lives in a similar climate can surely chime in more intelligently. Good luck. Please post updates - I love mysteries.
 
Sorry, I missed a couple of things. Ph is 7.4. I'm using the Taylor K-2006 FAS-DPD. The FC was 6 the CC was 0 and the TC was 6. The water temp is around 82 and of course varies but stays fairly high this time of year. I had a big problem while in California with high CYA. I did not know it at the time but while my Chlorine tested as fine (no FAS-DPD) I was having algae problems because of high CYA. I have a bucket of Trichlor tabs that I was going to give away, maybe I should keep and use them?
 
gsheltonlhc said:
Ph is 7.4. I'm using the Taylor K-2006 FAS-DPD. The FC was 6 the CC was 0 and the TC was 6.
Click to expand...
OK, that does clear a couple of things up. pH is fine and you're using a good test kit. Also, with FC and TC of 6, no shock process is needed. Your chlorine consumption is solely due to the low CYA level for your hot, sunny climate.

Your pump is being run sufficiently, so that eliminates my item 3 of testing anomalies due to the pump being off for an extended time while testing.

While on the subject of testing CYA, bright indirect lighting and consistency are important. I test my CYA monthly, on a bright sunny day between the hours of 10:00 AM and 3:00 PM to get maximum lighting. Here are the Extended Test Kit Directions.

A leak may be another possibility, as Agmike suggested, and is worth taking a closer look at. You can try the bucket test: Fill a bucket with water, mark the level of the water in the bucket, set it on the stairs and compare the water loss between the pool level and the bucket level. If the water level in the pool drops more than the water level in the bucket, that would indicate a leak. But the leak would have to be substantial - one I think you would notice - if that were the sole cause of the dramatic drop in your pool's CYA. But it's still worth doing this simple test.

If the bucket test turns up negative, then I'm about tapped out as to further possibilities causing your CYA loss that have not already been raised. As I mentioned in my initial post, there are a few things about CYA that remain a mystery.

Regular testing is still your best defense. I would also keep the trichlor pucks. You may be one of the few that could use those on a somewhat regular basis. Keep in mind that trichlor also lowers pH, so you will need to keep a close eye on that and raise it as needed using Soda Ash. You seem to have a good grasp on testing and the effect of chemicals added to the pool.
 
I will do the "bucket" test to be sure but there has been no increase in water usage and no visible water on the property. If my CYA is dissipating somehow, that's awesome! In California it never went away and just keep climbing. The ability to use the Trichlor pucks makes life a little easier. I feel confident enough to replace my test dummy avatar. Thanks for the help.
 

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