I haven't mentioned it up until now, but since Christmas the water coming out of the soda dispenser has smelled like rotten eggs. You have no idea how nasty sulfur coke is until you've taken a whiff. I noticed the smell starting a week or two before Christmas, but hoped it was a passing thing. I think I caught it first because I tend to drink soda water, which has no other flavor/scent to cover the smell. It got worse over the holidays while most employees were home and not helping circulate the water through the machine.

I should mention we have always had an intermittent sulfur smell from the water in the building, usually the hot water, but not always, usually in one bathroom, but not always. The plumbers from our service company always seem set on it being related to a bad anode rod in the hot water heater. This rod is also called the sacrificial rod, as its purpose is to be corroded/dissolved before the tank itself. They believe when it dissolves, it can cause a sulfur smell--more on that later.

From a bit of googling and discussion with fellow employees (and a bit of googling from them) we came to the conclusion that the building is infested with a form of bacteria that releases sulfur smelling gas (probably sulfur-reducing, see "How do I determine the source?", bullet point 3 at this link.) and the entire building needs to be very thoroughly chlorine-shocked and hopefully that will resolve the issue.

After two weeks and a couple of visits from plumbers from our service company (which included removing a corroded anode rod from the closest water heater to the soda dispenser) the recommendation from their plumbers was that we should flush the soda dispenser with a 50/50 solution of chlorine and water and then everything would be peachy keen. (As an aside, that's a heck of a lot of chlorine.)

I believe they came to that conclusion because they could not smell anything in other faucets or even in the nearby ice machine, and decided it was the soda dispenser itself. From my point of view, this makes little sense, since:

1. The water line going into the machine has gone from clear to black. The inside is coated with a thin layer of slime (produced by bacteria). The lines leading elsewhere in the machine are still clear. This indicates to me that the bacteria is originating in the building water.
2. The cold water in the building has smelled like sulfur at various times.
3. When I shut off the water to the ice machine (mistakenly) for a few hours and then turned it back on, the water running through the machine smelled strongly of sulfur. I believe this means when the water sits for a while the smell increases. A good deal of water sits in the pop machine, separate from the flow of water through the building, until someone dispenses it into a cup. So, the normal operation of the machine (or lack of constant operation, I suppose) would exacerbate the problem present elsewhere in the building.

Anyway, I bought a new incoming water line for $10, threw away the disgusting one, and chlorine-shocked the machine on Tuesday. I used a turkey baster to suck up about half a cup of chlorine and fill part of the new incoming water line before hooking it up to the water and opening the valve. The whole process took about two hours. Much of this was running the chlorine smell out of the machine and mopping up water, see "Cole's Law of Soda Dispenser Maintenance."

Cole's Law of Soda Dispenser Maintenance

One cannot work on the soda dispenser without a significant volume of water (perhaps carbonated, perhaps not) and/or syrup spilling across the floor.

Perhaps this is not true of all soda dispensers everywhere, but it unfailingly applies to the one we have.

Somehow the drain from the pop tray was pulled out of the drain in the floor, so that the water I was flushing through the system was just coming back to pool at my feet for a good couple of minutes before I noticed what was happening. I blame the plumbers for moving the machine to look at the filters, of course.

So now, after this fantastic adventure, the sulfur smell is gone from the pop machine, and still occurs randomly in the ice machine and bathroom faucets. The incoming water line is clear and clean. And, I have a feeling we've probably bought a couple months before everything turns black and eggy again. We shall see.

Oh, I said "more on that later," regarding the hot water heater, but almost forgot to mention why. Apparently one of the causes of sulfur smell for the hot water heater is just that it provides a nice place warm place for bacteria to live. Another, to be fair to the plumbers, can be that the corrosion of the anode supplies electrons that sustain the reaction of sulfate to hydrogen sulfide gas. Still, I'm betting on the bacteria.

And finally, for those of you skeptics who are thinking "Hey, this is city water. It's already chlorinated." Let me mention that I know the building once had well water hookups (there are two wellheads in the basement), and I think the building has harbored this bacteria for a loooong time. Since it isn't well water now, that says to me that if we were to shock the system thoroughly enough, it might actually resolve the problem, vs. a well water system, which would likely be a chronic issue.