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I am working with a distributor to install a salt system for a commercial indoor pool. I have only installed one of these units before, and I want to make sure this is the correct choice to go with. Aside from electrode failure what are some issues with these systems.
Keith B. Janus
Janus Mechanical Consulting

The biggest 'issue' with salt systems on commercial pools is that they are under-designed 90% of the time. There is much more to consider than the 'gallons' factor.

Ross,
I am little confused by that, you said largest problem is undersizing, but not the gallon factor... can you elaborate on that?
Keith B. Janus
Janus Mechanical Consulting

It has to do w/ the actual consumption of sanitizer.

Its not like a residential pool, where you size them per gallon of water. In a commercial pool you need to size it by, gallonage, and bather load and add a little for extra just in case. br>

The chlorine demand of a commercial pool is determined from the bather loading, daily pool-open hours, water volume, ? use of conditioner, effectiveness of filtration/circulation etc. Most important - you must know how many swimmers use the pool per day (worst case) and over what period of time those swimmers use the pool.

We see a lot of disappointed commercial pool operators that give up on their salt systems after a short period of time.

My suggestion from my observations regulating pools. Allow extra capacity for all the things Ross mentioned, they are as important as the gallonage alone. Calculate the unit size, double the size and install it with an ORP controller.

The ORP controller will turn the unit on and off as needed, the electrodes will last much longer, and you avoid some of the lag time problems with manually adjusting the units up and down to accommodate the fluctuations in bather loading and sunlight.

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Steve Keifer

Good comments.

A properly designed saline (salt) system will have the gram per hour production capacity to cater for the chlorine demand of the water plus swimmers (and other factors) within the hours the swimmers use the pool (per day). It is no use installing a salt chlorinator that takes 24 hours (or more) to produce what is required within the daily 'open' time of the pool.

This is a excerpted reply from Paul Sisson (Michigan Dept Board of Health) detailing the Michigan regs for chlorine capacity. Paul mentions me in this because the original message came from a distributor rep from a local distributor that I had been working with.

"Concerning sizing, we (and many other states) require a 10 ppm application rate for commercial pools. We have used this rate for decades. The theory is to apply 10 ppm, use 9 ppm to satisfy chlorine demand under heavy use, and leave 1 ppm as a residual.

Any chemical feeder must be able to supply 10 ppm against the flow rate. Converting all the numbers around, a commercial feeder must supply 3 lbs / 24 hours / 12,000 gallons of pool volume. This is based on feeding against our old 8-hour turnover.

This means for a typical 20' x 40' pool, 3' - 5' deep, and volume = 24,000 gallons, you need a feeder that will supply 6 pounds of chlorine per day. (The 8-hour turnover for a 24,000 gallon pool is 50 gpm).

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Rick Bays

Rick, thats a typical Health Dept (not much logic) response. How can they simply stipulate "24,000 gallons = 5 generators", with no consideration for bather load etc. The 24k pool may have 10 people use it per day, or it may get 250 swimmers in it during the day.

Our actual pounds per day are way under what that Health Dept says, but the systems work wonderfully and the water is always perfect - Recently completed projects we have done include:
14K pool, 50 swimmers, 3.2 pounds per day
10.3K pool, 200 swimmers, 4.3 pounds per day
40K pool, 50 swimmers, 3.2 pounds per day
98K pool, 150 swimmers, 6.4 pounds per day
500K pool, 300 swimmers, 27.5 pounds per day

My theory is, the previous chlorinating equipment is always left in place and if chlorine demand ever exceeds what the salt system can handle the operator simply turns it on to make up any shortfall.
It is economically not feasible to install salt systems which can produce 3 lbs per 12k gallons per day. That would mean that 500k pool mentioned above would need a system that could produce 125 pounds of pure chlorine per day - which is nothing short of lunacy. Thats almost 3 50lb drums of di-chlor. Bloody idiots.