Regulations for interconnection between potable and expansion tankfill

Looking for info about the plumbing into the expansion tanks. Is it mandated to have the connection a drop, with an air gap, to prevent back flow INTO the potable system?

Does anyone know what the specific phrase is to search the CFRs?


OK, here is all I can find but it is from the CDC training program for potable systems on passenger vessels.

Where is this in the CFR or USCODE? Anyone???

“Types of crossconnection.
There are direct crossconnections,
and those are under the
influence of backpressure and backsiphonage. And then indirect crossconnections
only subject to backsiphonage. Types of backflow prevention are nonmechanical
Air gap, nonmechanical.
This slide represents an air gap, which is a physical separation.
This separation has to be two pipe diameters or 2.54 centimeters, whichever is greater.
For example, if I had a pipe that was onequarter
inch, two pipe diameters would be only
a half inch. One inch would be required. This is the highest form of protection. Air gap
alternatives are a barometric loop or antisiphon


Where is this in the CFR or USCODE? Anyone???


The CG doesn’t provide a rule for everything, though it seems like it sometimes. Some stuff is governed “by reference” such as NFPA standards and even ABYC standards. The US Navy and the CG have very detailed manuals dealing with health and sanitation that go into great detail on potable water systems and testing. Those documents detail things like the air gap requirement. The CDC provides direction, as you have found and several of those guidance publications make reference to 40 CFR which has water quality standards.