Maintaining Chlorine levels during early spring

Hi Everyone,

I had a new 21K gallon gunite pool installed late last year. It was completed too late in the season to use and I had just enough time to close it before things started to freeze.

I read the old forum quite a bit and followed advice to raise the chlorine level prior to closing. I shot for about 15ppm. I read that Chlorine levels are generally maintained during the winter months but I did not find this to be the case. I pulled back the cover a couple of weeks ago and found no measurable chlorine.

I haven't opened the pool but my levels were all out of whack so I've been adding chemicals and using a submersible pump for circulation. This has worked pretty well (PH, Alk and hardness are all in check now) except for chrlorine. It's still chilly here in northern Delaware, but the chrloine is pretty much gone a few days after I add it. I've had it up to 10ppm a couple of times (using bleach) but a few days later it's gone. There were some leaves, etc, in the pool that I thought might be contributing to this so I removed them but this made no difference.

Any ideas why this might be happening? Is there some reason that I should try for a higher shock level? All I'm really trying to do right now is keep enough chlorine in there to prevent algae growth as things get warmer.

Thanks,
Lenny

I would suggest testing your cya level. It may be that you have none in there. I find that to be true of my pool each spring. I close with a cya reading, and open to none. Other people are able to maintain a cya reading throughout the winter. Some people have suggested that pools that turn into a swamp over the winter cause the cya to drop, but I open to a clear pool each year, so that isn't the case. Who knows where it goes! Another thing that could be happening in your pool is that you may have something organic in there that you can't see that is consuming your chlorine. I think your plan of just trying to keep enough chlorine in there to prevent algae growth until opening is reasonable, although if you find that you are having to add bleach very often, I'd go ahead and take it up a little higher than you presently are just so you don't have to add it so often. Can't comment on how high to suggest without knowing your cya reading. On second thought, with a gunite pool, you don't really have to worry about going too high with your cl as you do in a pool with a vinyl liner.

Thanks, Watermom.

The organic thing was my best (uneducated) guess. I removed the leaves as I said but there's still some junk in there and I don't have the filter running yet. It's still getting down near freezing at night and the water is cold, so I think I'll leave it alone until next weekend and go ahead and open the pool. Looks like the weather will be improving and since I'm new to this I'm going to open early to get a handle on everything.

My CYA was around 100 last year at closing (while I was still listening to the pool store and dumping tri-chlor in there :rolleyes: ). I did take a sample to the pool store when I first pulled the cover back a couple of weeks ago at they measured it at 50 but I've already found out the hard way that if you don't mix up the water somehow prior to testing you won't necessarily get a accurate, representative sample. I have Ben's test kit and I'll go ahead and test the CYA myself.

Lenny

Hi, Lenny,

Post up those numbers after you test and you'll get more good advice.

I'm betting you've got more organic matter in there than you think and that's where your Cl is going. Post results for FC, TC, pH, T/A, CYA, and CH.

See ya'

Dave S.

Also,

organic matter + no Cl + sudden low CYA = HUGE CL DEMAND

I've had this happen to me, and Ben wrote a post on what happens. Basically, with low Cl, there is enough of the bactieria present that can break down CYA. The big problem comes from the waste products of these bacteria...they create a enormous Cl demand. It will take lots to clean up the mess, but it will eventually slack off. Definitely get whatever gook you can out of there. That will help for sure.

Michael

Well, after running the filter for over a week and shocking a couple of times my pool is still devouring chlorine. The water looks very clear. There is a stain in the middle of the shallow end which looks like dirt. Other than that, the pool looks very clean.

On Saturday, I put enough bleach in to get me to 5 ppm, but it was pretty much gone the next day. So I put in 3 gallons of 10% which would get me to 15 ppm. That was down to about 2 ppm this afternoon. So I put in 4 more gallons of 10%, which should get me just over 20 ppm. If the pattern continues, this will be gone in a couple of days.

I also lowered the PH to offset the effect of the bleach and to get down to a PH level where the chrloine will be more effective. I brushed the pool as well (for the 5th or 6th time in the last week). I'm going to let the pump run all night.

Here are my test results from this afternoon before adding the chlorine:

TC - 2ppm (I didn't test FC today)
pH - 7.6
T/A - 120
CYA - 50
CH - 270

mwsmith2, one interesting thing to note about the CYA. When I closed the pool in December I had a CYA of 100 (thanks to my friends at the pool store :rolleyes: ). I drained the pool about 15 inches at closing, which was replaced with rain water. Now I have a CYA of 50. I read on the old forum that some people have a drop in CYA over the winter and that organic material or bacteria might be the reason for this. I wonder if this is more proof that I have the bacteria problem you described.

Thanks to all for the help. My plan at this point is to go into standard algae mode: 20ppm/filter 24x7/brush daily. Am I on the right track?

Thanks,
Lenny

Absolutely on track!! Keep that Cl up around 20 by constantly replenishing ( three times a day, if you can) and your pool will be sparkling and your Cl will start to hold. You have a good grasp of the issues:)

Dave S.

Yes, the "sudden drop" you describe comes from the biodegradation of CYA, of which the main waste product is ammonia, which as we all know, is the main waste product in urine. So, you basically have a whole buch of wee beasties peeing in your pool. :D Eventually, you will burn up all that waste product, but it will take awhile. The real test is holding Cl overnight. That way you eliminate the effects of the sun on your Cl levels.

Michael

I'll add my 2 cents worth here--one thing I like to do is keep two floaters going in the water and keep each one stocked with chlorine pucks. I find that that way I at least have a constant leak of chlorine into the pool, and that really helps to keep any growth of microbes/algea down.

Boris

Thanks for the responses everyone. Now I'll know what to do if I ever really have that bacteria problem :). Here's my latest tale of woe.

Thankfully, I realized what was going on the day after I last posted. I had my chlorine up to 22 and before I went to work the next morning I tested it again and it was holding strong. After work the chlorine was down to 9. Pretty fishy, huh? :D

My pool was built in the fall and opened late last year. The pool store that my builder turned me over to told me everything I needed to do to get the pool going. That included dumping in a bunch of di-chlor to shock and tri-chlor for regular chlorination. After just a 2 or 3 weeks they were measuring my CYA level at 100. I now know that it's implausible for the CYA to rise that fast without specifically adding CYA to the water, but I had no idea at the time.

I have Ben's test kit now and the results I published earlier were based on my testing, with the exception of CYA. I've been getting comfortable with the kit but hadn't yet added the CYA test to my repertoire, so I relied on my old friends at the pool store (they measured 50). After I saw what was going on with the chlorine I did the CYA test myself and found no measurable CYA. I went to another pool store and they confirmed this (although they measured a PH of 8.0, when I knew it was really 7.4 :rolleyes: ). I don't know why they are so off on their CYA test, but at least they're consistent! ;)

I've added CYA. I thought that I could use the pool stores once in a while just to confirm my test results, but I'm done with them. From what I've seen, test strips are a pillar of accuracy compared to the pool store.

Lenny

Just remember to give it a week to let your cya dissolve in your filter before you retest your level, add more or backwash. It takes time. And, as you have read on the forum, you don't want too much.

Watermom

Hi, Lenny,

Pat yourself on the back that you solved that problem despite what the pool store testing was doing to you. It misled you and everyone on the forum.

While I certainly think there are some good pool places out there that you can depend on, I am continually surprised by the number of posts here who've had inaccurate testing done. I then think of all the folks who never have an opportunity to come across a forum like this and how they must struggle through the Summer fighting their pools instead of enjoying them.

Ben, give yourself another star!!:D :D

Dave S.