Post-mix poisoning must be addressed

Over the past 30 years that I have been involved in the plumbing trades, I have seen, first hand, a number of incidents of carbon dioxide backflow into potable water from post-mix soda dispensers. The supplier of the post-mix machinery would invariably declare that the problem was not with his equipment, install a new post-mix machine and abscond with the original one.

Blue ice! A local restaurant noticed that its ice machine had produced beautiful aquamarine cubes overnight. A check of its water revealed a low pH (in the 5.0 range). The culprit? A post-mix dual check valve failure and a repeat performance by the supplier who provided new equipment and denial of responsibility. Funny how the problem always disappears with the old post-mix unit.

In another local incident, a young girl drank a post-mix soda and became violently ill within minutes. If you’ve ever seen “The Exorcist,” you’ll understand the term projectile vomiting. Her mother was understandably horrified, as was the restaurant owner. In order to avoid a lawsuit, the owner had to purchase new sneakers for the whole family.

Backflow prevention is serious and as a licensed tester, I take this issue to heart. So, I called Steve Hengst, York Water Co.’s guru of backflow prevention, to discuss my post-mix soda dispenser incidents.

I was surprised to find that there have been a number of similar incidents. I also was chagrined to find that the manufacturers of this equipment and the soda companies are reluctant or unwilling to change the manner of backflow protection that has been in use for more than 40 years!

Steve gave me copies of his Drinking Water & Backflow Prevention magazine, which contained numerous articles about this very problem.

One article by Tom Guy of Lancer Corp., a manufacturer of post-mix equipment, and another by Steve Grover of the National Restaurant Association, were enough to make my blood boil. Both indicated a belief that no changes to the existing dual check valve are needed because “failure rates are infinitesimal” (Guy) and “copper poisoning is relatively mild” (Grover).

Grover goes on to say: “The cost per unit to retrofit a vented dual check valve to an existing system is approximately $400 to $800. To install a reduced pressure principle assembly it is approximately $1,000 to $1,500.”

Is money the obstacle that keeps the soda industry from changing its machinery to a safer method of post-mix?

Think about every venue you attend, whether it’s a sporting event or a county fair, that has only one major brand of soft drink products. That doesn’t happen because the owners are in love with one particular beverage. It’s the money the soft drink companies or their distributors shell out to purchase the right to be the exclusive purveyor of that product. Many tens of thousands of dollars change hands over these issues at these events, and this adds up to millions of dollars.

Although Guy doesn’t reveal his basis for claiming infinitesimal failure rates, Grover cites reported cases of copper poisoning by post-mix machines from an nsf report based upon a voluntary survey of 2,100 water and health authorities. Of the 2,100, only 804 (less than 40%) responded — hardly a definitive study, in my opinion.

My belief is that plumbers have handled numerous incidents directly with restaurant owners; the owners, in turn, had the equipment replaced by the post-mix vendor, all of which goes unreported to any agency.

The problem of post-mix copper poisoning is real and needs to be addressed.

Both Guy and Grover raised the issue of venting CO2 into a confined space, and they are correct that this should be a concern. CO2 is a colorless, odorless, noncombustible gas that is slightly more than 1.5 times as dense as air.

Concerns regarding CO2 in confined spaces, however, can be dealt with easily and should not be used as a smoke screen to prevent or delay implementation of products to enhance consumer safety.

There is something you can do. Install either of these vented dual check valves: Watts Regulator #SD-3 (stainless steel) or the Conbraco Industries #4C-100 (plastic). Remember — no copper, brass or bronze between these and the post-mix unit.

The symptoms of copper poisoning come on quickly after consumption of affected beverages. The foul taste of the tainted water is masked by the syrup and the cold temperature required (40°F or less) to maintain good carbonation and often remains undetected prior to onset of symptoms. Nausea, vomiting, dizziness, chills, burning mouth and diarrhea usually occur within 5 to 30 minutes.

Backflow of CO2 occurs with check valve failure due to its much higher pressure than that in the potable water system. As the CO2 enters the potable water lines, it forms carbolic acid and attacks the copper tubing. If bronze fittings are in this mix, lead poisoning can also become an issue.

Even minute amounts of copper or bronze can cause the onset of these symptoms. As professionals you should be aware that the cleaning of fittings and tubing on potable water lines upstream of a post-mix machine can create dust that must be flushed adequately to be removed.

A simple and inexpensive pH test kit should be a part of your shop equipment so that you can document a post-mix incident. This procedure can help to keep you and your firm in the clear.

Dave Yates owns F.W. Behler, a contracting company in York, Pa. He can be reached by phone at 717/843-4920 or by e-mail at [email protected].