INDOOR pool test results -- advice?

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sevogas

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Mar 15, 2011
2
Calgary, Canada
Hello everyone,

I have been visiting this forum for a couple of months anticipating my becoming a pool owner, which happened Friday when we moved into a 10yr old house with a pool that was built during construction.

Please note this is an INDOOR pool, approx 15000 gallons. I became suspicious when I found some stabilized chlorine in the storage area.

So before unpacking, I took out the ColorQ that I had ordered and here is what I got at a pool temperature of 62 degrees:

FCl - 0.07
TCl - 0.28
pH - 7.6
Alk - 106
CH - 220
CYA - 96!!!!

I then decided to heat up the pool and retest the next day. The ColorQ manual says that CYA can read high at low temperatures, so here it is at 78 degrees:

FCl - unreadable
TCl - 0.12
pH - 7.4
Alk - 102
CH - 199
CYA - 111!!!!

I diluted the pool water with tap water by 50% and retested the CYA, and it came out to 56.

Please note the water looks clear, no visible algae, there is no smell of chloramines, and the vinyl liner was replaced 3 years ago. There a a few small windows in the pool room, but the pool does not really get any sunlight through them.

Right now it will just be me and my wife swimming, i.e. no pool parties. The previous owners were using a pool company to maintain the pool. Ideally I would drain the pool and refill to get rid of the CYA, but then I would have to replace the vinyl liner. Repeated partial draining and refilling (i.e. 10-25%?? I don't even know how much is safe to drain a vinyl liner pool?) would take a long time and waste a lot of water to get the CYA level down to 20. I know there is a method of using a tarp/plastic sheet to simultaneously drain and refill, but that seems like a big job....

Any advice? Do I need to add more bleach or is that futile with such a high CYA level in an indoor pool? Is it safe to swim in? Is it feasible to run an indoor pool with such a high CYA level? Any help much appreciated.
 
Welcome to TFP!

Yes, it is possible to run the pool with that CYA level. You can drain down until there is one foot of water left in the shallow end if you have to. But you can manage without any significant problems with CYA at 56, so I wouldn't bother with that. Use the same FC recommendations we make for outdoor pools. The main thing is to stop using any products that add CYA.

Your numbers are fairly good otherwise, as long as the water replacement didn't change anything other than CYA too much.
 
I have never known my CYA levels to get anywhere near that high with my indoor pool, however I would not try any drastic actions at this point. Maybe drain your water level down a foot or so and refill occasionally over the next several months and maintain your free chlorine level at the levels advised on the CYA/FC chart. As long as you don't get an algae outbreak and maintain your correct FC to CYA ratio you will probably be ok. Over time (as water is replaced due to backwashing, etc.) your CYA level will come down if you don't use anything that will bring it back up (stabilizer, di-chlor or tri-chlor). I generally find using MPS chlorine free shock is helpful to remove CC in my indoor pool as shocking with chlorine takes a week or more to drop back down to safe swim levels due to the lack of sunlight to break down the chlorine.

Ike
 
I'll bet chem geek sees this post and chimes in.....he understands the proper application of chlorine in an indoor pool really well.

I believe he will encourage you to reduce your CYA down to around 20 or so. That will allow you to use very little chlorine and still have the gentle buffer that CYA can provide......it's a good balance. As posted above, you can reduce it in increments but I would certainly get it reduced.

Currently, you FC is virtually non-existent and it seems to me you should immediately get enough in there to get to at least 2-3ppm.

Secondly, I would get a second test result on the CYA reading. ColorQ's are notoriously inaccurate on CYA and, while yours seems consistent, I would get it verified at a pool store with a standard turbidity test.
 
Yup, Dave said exactly what I would say. The thing with indoor pools is that without the UV from sunlight or from a supplemental oxidation system such as UV, ozone, or non-chlorine shock, they tend to build up CC more readily. We usually don't want the CYA level to be high though as Jason wrote, you can raise the FC level proportionately at least to have disinfection and algae prevention. Since you don't smell chloramines at this point, you could try managing your pool following the Chlorine / CYA Chart and do partial drain/refill over time to lower the CYA level.

The problem will be if you do start to build up chloramines and notice a smell. Your safest bet to deal with that, if it occurs, is to get a UV system (or an advanced oxidation system using boron-doped-diamond electrodes which would also work, but is likely more expensive).
 
Thanks for your replies!

So with my CYA running around 100, should I try to drain the water & refill enough to get it around 50? I know the ColorQ has issues with CYA readings, but I was finding it difficult to have the recommended test kits shipped to Canada. When I diluted my test sample by 50%, the CYA reading was almost half, so I was hoping that would indicate something about its accuracy.

Maybe there is no smell of chloramines because there is no free chlorine to make them? I will certainly consider getting supplemental oxidation such as UV or Ozone (probably UV so I don't have to worry about outgassing in an indoor pool). In the meantime, can I use non-chlorine shock to get rid of them if they occur? I am a bit worried that if I use bleach to shock the pool it will take a long time to get the free chlorine level down to normal because it is an indoor pool.

I hope this makes sense, I am new to this whole pool thing, but it sure seems like fun
 
sevogas,

I've got a ColorQ and a TFT-100 kit. If you're using the tablets for CYA and doing the test as it states (which I do), your CYA level should be dead on. I get VERY comparable values between these two tests when I check for CYA. Draining 1/2 your pool and obtaining a measurement of 1/2 certainly confirms my observations. My ColorQ was purcased in the Fall of 2010 for reference. My readings between both tests are within 5 each time I've ever compared. FC is usually about 2-3 ppm less with the ColorQ so you may have more chlorine than you think in your pool. My CH is always much lower with the ColorQ. pH is always very accurate along with ALY.
 
XsAllOverIt said:
I've got a ColorQ and a TFT-100 kit. If you're using the tablets for CYA and doing the test as it states (which I do), your CYA level should be dead on.
Click to expand...
The CYA test on the ColorQ is very sensitive to precise following of the directions, which many people are lax about. Even when following the directions perfectly, the precision is still not as good as it is on the black dot test.
 
sevogas said:
So with my CYA running around 100, should I try to drain the water & refill enough to get it around 50?
:
Maybe there is no smell of chloramines because there is no free chlorine to make them?
Click to expand...
Yes, it will be easier to manage your pool if the CYA is lower. And yes, when you raise the FC level you may find the CC rising as well and may get your smell. All depends what is already in your water.
 

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