Does a soda machine, ice machine or coffee maker need a backflow preventer?

Maricopa County applies the FDA Food Code to food businesses. Its Environmental Health Code adopted the 2017 edition, effective October 6, 2021. The county's construction guide then turns the code into requirements for each piece of equipment. Mesa goes a step further and lists the backflow device it accepts for each machine (City Code 8-1-9).

"RP" and "RPZ" both mean a reduced pressure zone assembly. Mesa defines a "dual check" as "two independent check valves with a vent to the atmosphere," acceptable only for low hazards. A double check assembly is the bigger, testable version with test cocks and shutoff valves.

Your city may be stricter than the county. Mesa's list is a good example, and the county guide itself says to check with your local building department, since it "may have more stringent regulations."

A soda carbonator mixes carbon dioxide into water under pressure. The danger is old and well documented. A study in Public Health Reports, now kept in the CDC's library, looked at illness from carbonated drink machines. The cases "seemed to occur only after a faulty check valve allowed carbon dioxide to flow into a copper waterline." The gas flows backward because "the gas pressure in the tank is greater than the pressure in the building's waterline." Carbonated water eats at copper, and the next drinks poured carry it. The authors' fix is simple: poisoning "can be prevented if contact between copper lines and carbonated water is precluded."

So the rule has two parts: stop the backflow, and keep copper out of the danger zone.

• The device. The county bases its carbonator rule on Food Code section 5-203.15. Its guide says an ASSE 1022 device, a vented dual check made for beverage lines, is "the minimum level of protection required for carbonator systems."
• The county's preference. The county asks for "an approved reduced-pressure backflow preventer or another approved, testable, continuous-pressure backflow device" between the water line and the carbonator. It calls a testable RPZ "highly recommended" and recommends a stainless steel one.
• No copper downstream. Tubing and fittings between the backflow preventer and the carbonator should be flexible line or stainless steel. The guide says: "Do not use copper or brass downstream of the backflow preventer." Mesa's code says the same for point-of-use assemblies. Copper can't be used downstream "where water is carbonated, deionized, distilled, or treated by reverse osmosis" (City Code 8-1-9).
• Filters go first. The county wants water filters on the supply side, upstream of the backflow preventer.

In Mesa the choice is already made. Its list requires an RP assembly on carbonated beverage dispensers.

Backflow protection on the supply line is only half the job. The other half is keeping sewage from backing up into food equipment. The county guide requires indirect waste lines with an air gap for "ware washing sinks, dish wash machines, soda fountains, prep sinks, potato peelers, ice machines, steam tables, steam cookers, ice bins," salad bars, dipper wells and walk-in condensate lines, citing the plumbing code (IPC 802.1).

An indirect waste line doesn't connect straight to the drain. It ends above a floor sink with open air in between. The details from the guide:

• At least 1 inch of air gap above the flood level of an approved floor sink or drain.
• Short runs. Indirect drain lines should not run more than 10 feet to the floor sink.
• One line per fixture. Each indirectly drained fixture needs its own rigid drain line, to avoid cross connections.
• The right receptor. A food prep sink or mop sink can't take another fixture's indirect waste.

Ice machines and ice bins are both on the county's indirect waste list. Ice is food, and a hard-piped ice machine drain is a direct path for sewer water into the bin.

The RPZ on a soda line needs a drain too. The county calls for "an approved funnel drain assembly with an approved air gap plumbed to a floor sink" for the relief valve. An RPZ that dumps water onto the floor behind the soda rack is a slip hazard and a sanitation problem. Mesa adds that a point-of-use RP's drain line must be at least as large as the assembly, routed to a floor sink or mop sink, with no flexible hose.

A testable assembly comes with a yearly test. Arizona's backflow rule, A.A.C. R18-4-215, requires required assemblies to be tested at least once a year by a certified tester. Mesa's point-of-use rule says the customer "must have the backflow prevention assembly tested annually and ensure that reports are submitted to the Department" (City Code 8-1-9). It also requires these assemblies to sit no more than 5 feet above the floor and be reachable for testing, even if an access panel has to come off.

The county asks for proof as well. For a carbonator RPZ, its guide says to "certify the backflow preventer and provide a copy of the certification for the backflow preventer test."

The small ASSE 1022 device is different. It has no test cocks, so no tester can certify it. If that's your only protection, the county says "a written maintenance policy must be in place that requires the annual inspection of these devices." That's one more reason the county leans toward a testable RPZ: the yearly test report is the proof.

### Three situations that come up

Opening a new restaurant or bar. The county reviews plans before you build, and the construction guide is its checklist. Show the carbonator backflow device, the relief valve drain and every indirect waste line on the plumbing plans. Missing air gaps are easier to fix on paper than after the floor sinks are set. If the space was something other than a restaurant before, read what a change of use means for backflow too.

Swapping soda vendors. A new beverage company may bring its own carbonator. Check that the backflow device stays in place and that no copper sits between it and the carbonator. If the new setup reuses old copper tubing, that's the exact problem the Food Code warns about.

Adding a coffee program. A plumbed espresso machine or brewer is a non-carbonated beverage machine under the county guide. It needs an ASSE 1022 device or an air gap on its water supply. In Mesa, check the list: non-carbonated beverage dispensers need a double check or a dual check.

Walk the bar and kitchen with this list:

1. 1Is there a backflow device between the water line and the soda carbonator, and when was it last tested?
2. 2Is the tubing after that device stainless or plastic, with no copper or brass?
3. 3Does the RPZ relief valve drain through an air gap to a floor sink?
4. 4Do the ice machine, ice bins and soda fountain drain through air gaps, each on its own line?
5. 5Do the dishwasher and any other submerged water inlets have vacuum breakers?

For the difference between the two testable assemblies you'll see most, read RPZ vs double check backflow preventers. If a soda-line RPZ keeps dumping water, why an RPZ backflow preventer spits water explains the causes. And for the yearly test and where the report goes, see commercial backflow testing requirements in Arizona.

HQ Plumbing & Air tests, repairs and replaces backflow assemblies on commercial domestic water and irrigation lines. Free estimates, upfront pricing.

For where the ice machine drain must end and how big the air gap is, see how to drain a commercial ice machine legally.