Shocking does not work...help please.

Jump to latest Follow Reply
The city water with .6 ppm CC (you're lucky -- my water is about 1 ppm CC) is monochloramine since many municipal water districts are switching to using monochloramine instead of chlorine as their disinfectant residual. Fortunately, monochloramine is readily broken down through breakpoint, but if done with high chlorine levels it can result in nitrogen trichloride (which smells and is very volatile and irritating).

The 0.2 ppm CC requirement borders on insane (0.5 ppm is much more reasonable, though is still a challenge to achieve in most indoor pools). It's much more important to have a requirement minimizing specific contaminants such as nitrogen trichloride and chloroform, but such test equipment measuring air and water quality is expensive. Many types of CC are relatively innocuous and some are relatively persistent. This is why I think it's best to prevent their formation in the first place, either through use of MPS on a regular basis and/or by using a small amount of CYA in the water to cut down their formation rate, but the use of CYA hasn't been proven yet in a real indoor pool (it's obviously used all the time in outdoor pools).

Clearly measuring CC during or soon after high bather loads isn't fair since there's no way you can break down the ammonia/urea fast enough. Measuring it at the start of the day is more reasonable.

I wish someone would try the CYA and see if it indeed slows down CC formation by a factor of 10 or so as theory predicts (assuming similar FC levels). It will also slow down breakpoint itself but should still be fast enough to keep up with typical bather loads. Too much CYA, on the other hand, would slow down breakpoint too much and would lead to a buildup of monochloramine during high bather loads (which seemed to happen in some indoor pools that used Trichlor tabs in feeders and had 100+ ppm CYA -- see this link for an example). At the other extreme with no CYA, nitrogen trichloride would form in higher quantities (due to the higher hypochlorous acid concentration) and is more common at lower pH as described in this link.

Richard
 
I was probably being nice by saying their water was at .6, you're 1.0 number is actually closer to realistic.

One of our locations inadvertently did try your method of adding CYA to the indoor pool but as you noted their levels increased to unsafe amounts and had to be stopped. The operator decided instead of adding chlorine by hand as needed to just float Tri-chlor which is a no-no. She had to drain large amounts of water to fix the high CYA issues.

One problem I have with adding small amounts of CYA to my pools is the Texas Dept. of Health Standards for Pools and Spas clearly states on the very last page of their document......
"Stabilizer shall not be used in indoor pools or spas or brominated pools or spas."

This only leaves the MPS method to try and help solve the issue.
 
Perhaps the Texas Dept. of Health Standards can explain how they can justify using CYA for outdoor pools and not indoor pools. It's one thing to say it isn't needed for indoor pools due to a lack of sunlight (which is only partially true), but quite another to ban its use completely, even in low amounts. It makes no logical sense whatsoever and doesn't take into account CYA's moderating role for chlorine.

If you have contacts at the Department, I can try talking to them to see if they can give you a waiver to at least try a small level of CYA -- probably 10 ppm and certainly not more than 20 ppm. Let me know (you can PM me using "chem geek").

Richard
 
I'll see if I can read back on the info I have on it, all I really know off the top of my head was the CPO instructor warning those of us with indoor pools to not add anything containing CYA or stabilizers to our pools. Something about it building up in our pools and causing bathers to become ill.......especially young bathers....? That's all I know, but I'll see if I can find out any more.
The CPO instructor seemed pretty adamant about this since she drilled it into my head. :)
 
I think the instructor was referring to using ONLY stabilized chlorine, such as Trichlor tabs in a feeder, as CYA will build up over time and that does lead to various sorts of problems. However, the same thing is true for outdoor pools. We're not talking about switching to using stabilized chlorine, but rather to add only 10 ppm CYA and then use unstabilized chlorine as you have been doing so there will be no buildup of CYA over time.

As for young bathers becoming ill, it's ironic because I believe that not using any CYA at all may be contributing to that very problem in many indoor pools. Too little CYA means a greater generation of disinfection byproducts such as nitrogen trichloride and chloroform (this is a well-known fact in the water treatment industry which is why they try and use lower concentrations of chlorine with longer contact times). At the other extreme, too much CYA means too slow a breakpoint and buildup of monochloramine. Either way can lead to respiratory illness and ocular problems. I'm proposing using an intermediate amount that should minimize these two sets of problems.

Anyway, if you find out more, let us know.
 
I might be willing to try this even though...... :?

The CYA level I would aim for would be around 10 PPM and no more correct?
I should only need to add CYA once and it's going to remain until I drain the pool, or mostly drain it....correct?
If I do add it to one of my pools as a test, should I bring the CYA level up gradually or all at once?

I can not risk having the pool not usable even for one day so I need to err on the side of caution, not to mention the location I would want to try this on is about an hour drive so I try to limit my 'emergencies' if you know what I mean.. :wink: :wink:

Lastly, would you still recommend a non-chlorine shock in combination with CYA or just CYA?
This pool as mentioned, has a SWG and an O3 ozone system. The ORP isn't actually used any more since we went did away with a Pulsar auto feeding unit.

Another thing I thought of....
If I try a non-chlorine shock I should use a different test kit? We currently use the dry powder method to test both free and total chlorine.

Thanks for the great help, I do appreciate it. :)
 
Subslug, welcome here :!: :wave:

I don't presume to have the answers, but I believe Richard was recommending 10-20 ppm CYA for the indoor pool.
Always shoot a little low when adding a chem that needs dilution to remove!!! I don't think that there are any testers that will test cya @ 10 ppm, but you've got a very good idea of the gallonage in the pool in question, as a 'test' anywhere between 10 -20 ppm cya should do.

It is my understanding that there is a special test for non-chlorine shocks, which eliminates the false CC readings - others will tell you the kit.

Again, welcome here!!! (I always like seeing other pool pros that care enough to research the things they don't know :goodjob:)
 
I don't think you are taking a risk, but to play it safe anyway let's shoot for a small amount of CYA -- specifically 10 ppm. And waste is right that you can't test that low with the standard turbidity test (perhaps an electronic test might work) since they only go down to 20 ppm. Nevertheless, you'll see a small amount of cloudiness in the CYA test even though the black dot doesn't disappear completely.

Yes, the CYA stays there and can only be removed through dilution. Even then, some stays stuck to pool and pipe surfaces so a very small amount will be there for a while, but with a small effect.

Since there isn't that much to add, I would add it in measured amounts and you have several options to do so. One option is to use Dichlor as your source of chlorine for a short time and realize that with every 10 ppm Free Chlorine (FC) you add with Dichlor, you also add 9 ppm to CYA. In 25,000 gallons, it takes 4 pounds of Dichlor (dihydrate) to add 10.6 ppm FC and 9.7 ppm CYA so figure on that cumulative amount and then switch to your regular unstabilized chlorine source after that (such as the SWG).

Another option is to add CYA directly, but it dissolves slowly unless you put it in panty hose or a sock and hang it over a return flow. 2 pounds of CYA in 25,000 gallons will add 9.6 ppm CYA and might take a couple of days to dissolve using the sock technique.

You won't have to shut down your pool at all when adding CYA using either of the above methods and you don't have to add it all at once and in fact won't with either method (unless you really want 10 ppm FC added using the Dichlor all at once).

I don't think the non-chlorine shock is going to help you get rid of existing CC, but you can try it with a bucket test so as not to waste a lot of money on it. As waterbear and others have said, MPS is best used as a preventative to not have CCs form in the first place. I'm hoping that the use of CYA will do the same thing to some extent (by reducing disinfecting chlorine concentration so slowing down CC formation). I don't have a solution for you to get rid of the CCs you already have, but if we cut down their formation via the CYA, then they should go down with dilution of the water and possibly air exchange (if they are volatile) over time.

What FC level do you normally maintain for this pool? With the 10 ppm CYA, I would set your FC target to 2 ppm FC for safety assuming that's around where you have currently. If your current FC is higher, that's OK though the 10 ppm CYA won't have as much of an effect in that case but I'd still try this low CYA amount before moving any higher.

By the way, with an SWG that uses 3000 ppm salt and with chlorine with no CYA, your pool is VERY corrosive, especially to stainless steel. We've had a few reports of indoor SWG pools with corrosion and all had no CYA whereas outdoor SWG pools with CYA don't see such corrosion or certainly not as quickly (as within one year). Perhaps if you are keeping your FC at 2 ppm or below then you are stretching this problem to 2-3 years as the pools with corrosion within one year were at 3-5 ppm (assuming it's linear and it probably isn't). The CYA will cut down that corrosion rate significantly by lowering the disinfecting chlorine (hypochlorous acid) level.

There shouldn't be a need to shock the pool, at least not with chlorine, since it should be continually shocked. A weekly dose of MPS might be useful to handle some organics that chlorine might not handle as well and possibly to have some residual to oxidize ammonia and organics before chlorine gets a chance to (as you read earlier, this is debated in terms of frequency of MPS dosing needed to do this), but let's do one thing at a time so we can see the effect of each step separately.

Make a mental note of the degree of odor in the current pool situation and the complaints (if any) of flaky skin, frizzy hair, faded or degraded swimsuits (including elastic degradation), etc. We'll want to see if that changes after adding the CYA.

Richard
 
One option is to use Dichlor as your source of chlorine for a short time and realize that with every 10 ppm Free Chlorine (FC) you add with Dichlor, you also add 9 ppm to CYA. In 25,000 gallons, it takes 4 pounds of Dichlor (dihydrate) to add 10.6 ppm FC and 9.7 ppm CYA so figure on that cumulative amount and then switch to your regular unstabilized chlorine source after that (such as the SWG).
Click to expand...

Having never used Dichlor let me ask...
We ordinarily shock our pools weekly using Cal Hypo, could I simply add 4lbs of Dichlor, replacing Cal Hypo., as a shock treatment and thereby increase the CYA level to 9.7 ppm in one fail swoop? Sounds too easy. :)

I assume shocking with Dichlor is acceptable?

Make a mental note of the degree of odor in the current pool situation and the complaints (if any) of flaky skin, frizzy hair, faded or degraded swimsuits (including elastic degradation), etc. We'll want to see if that changes after adding the CYA.
Click to expand...

Don't get me started on this.....I'm sad to say we actually lost an employee last week claiming of constant skin rash and I have noticed an odd smell in that pool room for a while now....I had always assumed it was coming from floor drains but I constantly bleach our decks but it doesn't help much. Our pool chemistry numbers are always right on with the exception of the somewhat high CC numbers.

Anyway, let me know what you think about shocking/super-chlorinating with the Dichlor, if you're cool with that I'll proceed.

Thanks chem geek and waste
 
Shocking with dichlor should be fine. One thing to keep in mind is that dichlor will lower the PH some (slightly acidic when added, more acidic when the chlorine gets used up), while cal-hypo is more or less neutral (basic when added, acidic when the chlorine gets used up).
 

Enjoying this content?

Support TFP with a donation.

Give Support
JasonLion said:
Shocking with dichlor should be fine. One thing to keep in mind is that dichlor will lower the PH some (slightly acidic when added, more acidic when the chlorine gets used up), while cal-hypo is more or less neutral (basic when added, acidic when the chlorine gets used up).
Click to expand...

Lowers the pH, that'll be a change.
Cal Hypo always sends our pH skyward when we shock so having it drop will seem funny. :lol:
I've always assumed it was just a false pH reading though, I try not to adjust for the increase until we're sure it's actually high pH and not just the chlorine causing it.

Thank You
JasonLion
 
Just to update:

I've added dichlor to this pool, 3lbs initially and 1lb each week for 2 more weeks so I assume I should have some level of CYA in the pool.
My question is since this is such a low level of CYA how am I to test for it and, how will I know how much to add to the pool as needed?
I have CYA tests that come with our Taylor 2006-k kits, although we've never used them but anyway, I'll run a test this evening while at the location and see if it reads any level of CYA.

I'm just not sure how much to add to maintain 20ppm and how I'll know when to add it........make any sense? :?

We've started leaving the pool uncovered every night now and I'm considering non-chlorine shock maybe once a week to help lower the CCs.
 
Measuring low levels of CYA is tricky. One way to approach it is to keep track of the total amount of dichlor used and calculate from there. Longer term it is nice to have some other number that only changes from splash out, salt works if you have a SWG, CH works if your fill water has zero CH and you aren't using cal-hypo, and use that as a proxy for CYA. With that approach you assume CYA goes down by the same percentage that the proxy went down.
 
Ahh, so if salt levels aren't dropping then CYA levels probably aren't either. Makes sense.

We've cut way down on wasting water. We now only add water when needed after backwashing where before they wasted about 1/3 of the pools water per week. I can only guess the reason they wasted this much was due to their using stabilized chlorine in the past and just never got off the heavy wasting practice. All we use now is either the SWG or Cal Hypo so high CYA levels isn't an issue any more. Some in our company had the impression that wasting and refilling also lowered their combined levels, which just ain't true :wink: in my case at least it's not.

I tested for CYA last night but as figured none showed on the test so if we do have any in the water, it's low levels. Looking back up in this thread I assume I need to have at least 20ppm before it even registers in a test.
I think I'll go on and add 1lb per month and test weekly unless I notice CYA in the testing. That should be safe.

I'll update this thread as some time goes by and let you and chem geek know how this low level of CYA works.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply