Ozone supplementation for indoor pool

[dmccarthy]

I have a 24,000 gallon heated, indoor, gunite, commercial pool currently sanitized with bromine tabs via an offline feeder. It has been brought to my attention by several of the experts here that using bromine tabs over time causes a build-up of DMH which reduces the effectiveness of the bromine over time. Also, since we are regulated by the state (Massachusetts) it is my understanding that I am not allowed to have any CYA in an indoor commercial pool (however I trying to find more clarification on this). Traditionally I have not had any and I am changing the water in a few weeks and now would be a good time if I was to change from bromine to something else.

I have been trying to find a different way to sanitize and have explored SWCG and liquid chlorine/acid ORP/pH systems, but I am hesitant to go with SWCG for my indoor pool. If I stayed with bromine I would be interested in not using the tabs if possible and read somewhere in TFP that ozone might be a helpful secondary sanitizer for indoor bromine pools? We have a high bather load and I am trying to ease the management as well as the build-up of CC over time that we experience after several months. We typically change the water annually due to this.

I was told to just add straight bromine until the water reaches the desired level and then just use liquid chlorine to avoid DMH build-up over time? If that is the case would and ORP for liquid chlorine make sense as well? I was thinking the ozone to help with reducing chloramines at the very least. Any suggestions would be appreciated.

Thanks,

Darin

24,000 gallon indoor gunite pool 92 degrees
offline brominator
hayward tristar VS 1.85hp pump
hayward pro-series 500lb HR sand filter
Raypack 333k natural gas heater

 

[JVTrain]

You can certainly build a bromine bank by adding sodium bromide to 30-40 ppm, then use only bleach/liquid chlorine to activate your bromide bank to bromine. This would eliminate DMH build up over time from using tabs. For an indoor pool with high bather load, supplemental ozonator or a preferably a UV system would be helpful in reducing CC build up.

Short of a UV system, you could try using MPS (monopersulfate) to eliminate some residual CC. MPS is better at breaking down difficult CC species than bromine or chlorine. Keep in mind that for up to 24 hours if you test for CC after using MPS, the MPS may register as CC.

EDIT: Taylor states that it's 8 hours that MPS can interfere with CC readings. However, this is subject to how much MPS you use... There is also an MPS interference remover reagent, but it's quite expensive.

I would look into whether or not you can use CYA in your commercial pool. The ability to use ~20 ppm CYA in your indoor pool would do wonders for your FC stability and ease of maintenance over using bromine.

 

[dmccarthy]

Thank you, I called a local CPI that have take the CPO course through in the past and I am trying to get clarification on whether CYA is allowed in an indoor commercial application in Massachusetts. It seems you would prefer UV over Ozone, is there a particular model or brand that you would recommend I look at? I am thinking that I would oversize the application a bit as we have a lot of bathers for a 24k gallon pool/hour/day/week and it seems like most of them are sized by GPM for recreational/residential use. Or am I wrong? We have all 2" PVC throughout and our pump runs 24/7 about 60-70 GPM (based on the FlowVis meter installed). I have been told that the UV light will also accelerate FC break down. If I find out I am not allowed by the state/city to add CYA to our commercial indoor pool would the breakdown of FC from the UV be so much that it would difficult to stabilize the FC levels, or would the impact be no greater than the normal use from bather waste that doesn't use a supplemental system like UV/Ozone? Forgive me for the last question here (as I have been accustomed to adding bromine tabs to an offline brominator and shocking 1-2x weekly as needed until it is time to change the water) but how do you measure for 30-40 ppm of sodium bromide? Is it the same as testing the FC-FB with taylor test kit that we usuaully use that was recommended by TFP? I would usually just look to make sure it was 4-6ppm free bromine when we test 4x/day. Thanks

 

[JVTrain]

Get a UV that is properly sized or slightly oversized for your GPM. I'm not an expert in UV but the risk with a commercial ozonator is that when they malfunction, ozone isn't healthy for swimmers if excessive amounts are produced indoors (bad for lungs). If your UV malfunctions, it's likely just an expensive bulb replacement, not a health risk.

UV will slightly increase your chlorine demand. Not as much if you are permitted to use a small amount of CYA. Likely unnoticeable FC demand increase if you are able to use CYA. Certainly negligible compared to bather waste FC demand.

If refilling and sticking with bromine, the only way to measure your bromide level is to assume (know) that your bromide level is zero in a fresh fill. Have a good estimate of your pool volume and then dose with sodium bromide based on that volume, targeting 30 ppm. See the instructions on the bottle for dosage, sodium bromide dosage is not included in Pool Math in any way. There is no method to directly measure bromide level. You have to know your volume and dose up to 30 ppm based on that. You can only test for bromine itself, which is formed when you add bleach. The reason you add 30 ppm of bromide is that over time, bromide can decompose and outgas very slowly so you want to make sure you have enough in there for at least several months should any outgassing occur. You would test the same way for bromine, but you'll only have bromine after you've added the bromide bank AND added some bleach/liquid chlorine. Bromide must be oxidized to bromine before it is useful as a sanitizer.

For the Taylor test kits that are used for FC, such as the FAS-DPD chlorine test included with the K-2006 and TF-100 kits, 1 drop at 10 mL = 1.25 ppm Bromine. 1 drop at 25 mL = 0.5 ppm Bromine.

 

[dmccarthy]

If I stayed with sodium bromide for this indoor pool would you recommend an automatic liquid chlorine feeder due to the high bather load? I am trying to avoid having to add larger amounts of liquid chlorine nightly/weekly and wonder if this would be a better option going forward? Also, where is the best location to install the UV lamp? Before or after the filter? After the filter before the heater? Or after the filter after the heater? Thanks

 

[JVTrain]

If you're insistent on sticking with bromine and/or cannot use CYA, a stenner or other type system to dose chlorine directly into the system would be the easiest for maintenance, with some added equipment upkeep and adjustment. Could also continue to use it after switching to chlorine.

UV lamp should be installed after the filter, always. If you were to also have a stenner or SWCG, the UV should be before the injection point or SWCG. You could install before the heater, but I don't think it would matter either way. If you want to know for sure, contact the manufacturer before installing. Pentair - BioShield®

Pump -> Filter -> Heater -> UV -> SWCG/Stenner injection

Like when installing a SWCG, it's helpful and required to also plumb in a bypass loop. This makes it much easier for service/replacement.