Balancing the Water in my Spa

[Txmat]

I have a 325 gal Hot Springs spa with an ozonator and Silver Ion Cartridge. The ozonator runs all the time. I have just refilled the spa and here are my test results:

FC .5
CC 0
PH 7.2
TA 350
CH 260
CYA 0

The manufacturer recommends TA of 125-150, CH 150-200, PH 7.4 - 7.6. They also recommend using MPS and Dichlor as sanitizers. They recommend using sodium bisulfate to lower TA and soft water (which I do not have) or stain and scale control to lower CH.

I know by running the jets I can raise PH and lower TA although it will sure use a lot of electricity to run the jets that long. What do ya'll think I should do to get this water balanced?

 

[chem geek]

I think you should significantly lower the TA and follow the Using Chlorine in a Spa procedure, aka the Dichlor-then-bleach method.

 

[Txmat]

Thanks. I read in the link that you said some people with ozonators did not like the way PH was affected. Do your recommendations change in light of the ozonator running 24/7 and the Silver Ion cartridge? Should I use MPS & less chlorine or not use MPS at all?

 

[chem geek]

I think we've pretty much resolved the rising pH issues even when using an ozonator. Having the TA be low, even 50 ppm, and also having around 50 ppm Borates seems to work well for nearly everyone. The downside with an ozonator would be if you don't use the spa frequently in which case the ozone oxidizes some chlorine to chlorate increasing daily chlorine demand. If you use the spa frequently (say, every day), then the ozontor cuts down chlorine demand (sometimes by half) by oxidizing some of the bather waste so that chlorine doesn't have to.

I wouldn't use the Silver ion cartridge unless you were wanting to go with a nearly chlorine-free approach. Nature2 (which uses silver ions) with non-chlorine shock (MPS) at hot spa temperatures kills pathogens quickly so that chlorine is only needed if there are water issues such as cloudiness (though that usually doesn't happen if you have an ozonator). So it's up to you which way to go. The silver cartridges plus MPS are quite a bit more expensive than Dichlor-then-bleach so unless you were trying to avoid chlorine you don't need your silver cartridge.

 

[Txmat]

Thanks for the very clear explanation and advice. I have a silver cartridge and MPS on hand so I will use it this 4 month cycle and then switch to the Dichlor - bleach- Borate method. I do not use the hot tub regularly, particularly in the summer, so if I understand your first paragraph I may have a higher chlorine demand with the ozonator than I would if I used it more frequently? I have the TF-100 test kit that I use on my pool and hot tub. I also have MPS test strips. I believe I have read that MPS shows up as FC in the TF-100 test. How do I know how much MPS & Dichlor to add while I am using up the Silver Ion? I can follow the manufacturer's amount and schedule, but I prefer to follow test results. Thanks again for your help.

 

[PaulR]

I believe I have read that MPS shows up as FC in the TF-100 test.

MPS shows up as CC (not FC) in the FAS-DPD test.
--paulr

 

[Txmat]

Since I use the Pool Calculator to determine how much chlorine I need to add to bring up the FC, can I still use it to determine the chlorine need and the MPS strips to determine the MPS need and ignore the CC as long as the MPS and FC levels are OK?

 

[PaulR]

According to what chem geek said, if you're using silver ion + ozonator + MPS, you shouldn't normally need any dichlor, so there would be no need to test for FC/CC. You would just watch the MPS level, and reach for the dichlor only if your water started having issues.

If you decide to switch to the dichlor-then-bleach method (which is what I use), then you're done with the silver and don't need the MPS anymore, so again there's no particular interference issue to deal with.
--paulr