Suggestions on switching from Bromine

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dmccarthy

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Aug 8, 2015
65
Jeffeson, MA
I currently have a heated indoor gunite commercial bromine pool at work and will be changing the water out in about 3 weeks and I am considering changing from the off-line brominator that I have been using to something else to sanitize and would appreciate some suggestions. I would like to switch to SWCG, however I am a bit worried about corrosion of the concrete/fixtures/doors, locker rooms, etc as it is indoors. Anyone have any experience with this? If not salt, what would be a good recommendation as there is very high bather load weekly (about 40-50 bathers/day x 5-6 days/week with an average of about 1 hour each and a max at any one time of about 10 bathers).

I was made aware that over time the constant addition of the bromine tabs builds up DMH making my bromine less effective over time and most-likely contributing to some of the issues we have over time where at even high levels of bromine I can't get the water clear. As it is an indoor commercial pool in MA we are regulated by the state and not allowed to have any CYA in the water so I have to keep my levels at 1-3 for FC and/or 4-6 for Bromine. This becomes a problem over time as at those levels I can't seem to get the water clear without going substantially higher due to what I am assuming is the DMH build-up issue?

Also, any suggestions on installing an ORP sensor in this scenario and what exactly would that do? I know a lot of questions, but I would like to automate as much as possible and/or look at what the easiest and most-effective solution would be for our situation. It has also been suggested to just add bromine at the beginning to build up the bromine bank and then just use liquid chlorine.

Thanks,

24,000 gallon gunite indoor pool
haywood 500lb HR sand filter
Haywood TS VS 1.85hp pump
off-line pentair 6lb automatic brominator
Raypack 333,000 btu natural gas heater
 
Are you sure about not being able to use CYA?

This link has a version of the MA public health code that says CYA levels between 30-100ppm are ok (435.29) - http://www.mass.gov/eohhs/docs/dph/regs/105cmr435.pdf

It is old (circa 1998) but it is an active document. Do you have a local county or town code that places an additional restriction on CYA?

In any case, chlorine is fine to use in an indoor public pool BUT you are going to need to add on a supplemental or secondary oxidation source such as UV or potassium monopersulfate (MPS). In high bather load situations chlorine will form lots of combined chlorine compounds (bromine does too) as well as trihalomethane's (THMs). Secondary oxidizers like UV or MPS help to oxidize bather waste without created irritating and dangerous chlorinated organic compounds.

In order to maintain the required 1-3ppm of FC, you are going to need a chemical metering system that will allow you to add chlorine as needed (one for pH control would be a good idea too). Chlorine can get used up rapidly and, without any CYA in the water, you are going to want to stay within 0.5-1.5ppm FC for bather comfort. With no CYA in the water, you can invest in an ORP-based control system to help maintain more consistent FC levels.

I would also consider using a commercial grade coagulant system (such as SeaKlear PRS 2-part clarifier) to help with water clarity issues. These types of products should be used when no one is bathing for optimal performance and I like the SeaKlear product because it will specifically work to help mitigate exposure to cryptosporidium oocysts that are transmitted in water from fecal matter ... sadly not all swimmers in a public pool engage in good hygienic practices.
 
Thank you, I contacted the instructor that taught my CPO course a few years ago and I am waiting to hear back from him on whether CYA is permitted for indoor commercial applications in MA. I am almost positive that is what I was told and I thought it was at one of the courses I took, but I can only find the same document you have found which seems to state it is allowed, but does not specifically reference an indoor pool. I have been using the seaklear PRS 2-part clarifier, but I think I probably have too much DMH build-up or high TDS at this point as it does not seem to be totally clearing the water, but it does help a bit when applied, but I am changing the water in 2 weeks anyway.

I would like to switch to SWCG, but the more I keep reading I am just really concerned about what seems to be the added risk of corrosion as the pumps, heater, etc run year round 24/7 and it seems that an in-line sacrificial anode and maybe even other zinc anodes strategically placed around pool equipment can only help mitigate the corrosion issue and it could still be a problem long-term? We do have an ADA stainless steel pool lift that has to stay in the water all the time as well and I really don't want any staining/corrosion issues.

Lastly, since I was not the original owner of the pool I was not there when the decking and original equipment was installed 20 years ago and I am slightly concerned that the possibility exists that maybe everything was not bonded properly as I am slightly concerned about what I have read about galvanic corrosion if the pool equipment was not properly bonded to the grid. The heater and pump definitely have a copper wire that they are both connected to and that goes into the concrete and I assume everything was done correctly and had to pass code as none of the lights or railings have corroded over the years, but it seems SWCG increases the chances? Unless I have said anything that you think is not true or the risk is much less than I have been reading. My SWCG at home is great and hardly any maintenance at all.
 
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Definitely do wait until you can get confirmation on the CYA for an indoor, commercial pool. CYA is not absolutely necessary for an indoor pool BUT it makes the chlorine much less harsh on bathers if you can add a minimal amount. Typically for an indoor chlorinated pool, you'd want 20-30ppm CYA for chlorine buffering which results in greater bather comfort since the active chlorine levels (hyochlorous acid/hypochlorite) are moderated. We have an entire advanced chemistry post on the topic for further reading if you need scientific backing for the change-over.

If you wanted to switch to salt, you would need a commercial grade SWG which produces higher levels of chlorine (the commercial Pentair unit generates 6lbs of chlorine gas per day) BUT they also typically require slightly higher salt levels (~5000ppm for most commercial units). This is still a lot lower than seawater BUT I would still caution to make sure the pool equipment can handle it. Any metal in the pool needs to be marine-grade stainless steel (316/316L stainless) OR marine-grade brass. Aluminum should not be used around the pool at all. Concrete surfaces are fine as long as they are hosed down periodically.

So, if chlorine is in your future, I would suggest you lean towards a chlorine injection system (liquid chlorine injection via Stenner pump). I would also suggest using an ORP probe to control it but only if you plan to keep your CYA down near 20-30ppm (or if CYA is not allowed). ORP probes can be a bit of a pain to dial in but, once you establish a baseline for the pool and get it functioning, it can help to automate the sanitation. As always, you want to make sure the pool is correctly sanitized by using an independent test kit (the Taylor K-2006-C is what you want) and you should make sure ORP is calibrated to that.

You should also consider installing a commercial grade UV sanitizer system. UV can help a lot to breakdown and oxidize organics. This will greatly reduce the chlorinated by-products (chloramines and trihalomethane's) created and allow you to keep a more stable chlorine level in the pool. Bather waste is your biggest pool water enemy in an indoor high bather-load pool and you need to design a sanitation strategy around that. Ozone is not good choice because it's an indoor pool and you don't want air quality to suffer. I would still continue to use the SeaKlear PRS system with chlorine as you want the added protection against cryptosporidium oocysts - not all bathers are conscientious of others and some people will swim knowing that they have "fecal issues".
 
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