Thread: Supply pipe passing through return air duct

I found a copper water supply pipe passing through a return air duct. Air duct is actually a joist bay with sheetmetal bottom. Galvanic corrosion where copper meets sheetmetal. Pressure loss in ducts. Condensation from uninsulated pipes inside ducts. What do you guys say? What does code say?

Thanks.

Originally Posted by Stanley Chow

I found a copper water supply pipe passing through a return air duct. Air duct is actually a joist bay with sheetmetal bottom. Galvanic corrosion where copper meets sheetmetal. Pressure loss in ducts. Condensation from uninsulated pipes inside ducts. What do you guys say? What does code say?

Thanks.

I've seen that too. I don't think code addresses it. In general, I think galvanic corrosion is the biggest risk, although I've never seen that happen. I write it up as a non standard installation. I've seen PEX and PVC run the same way which removes the galvanic corrosion issue, but still non standard.

Not allowed under the Code. You aren't supposed to run anything in the return line that could potentially contaminate the air stream.
IRC books at my office, can't look up the section right now.
Write it up as defective and explain why

Thanks guys for your replies. I appreciate it. MARCUS....when you have a free moment, could you tell me what code sections apply? I couldn't find it in the IRC.

M1601.4; M1801.8; M1601.3.1 per your picture;

Originally Posted by Markus Keller

M1601.4; M1801.8; M1601.3.1 per your picture;

I don't see how those references apply to the photo.

601.4 Contamination prevention.
Exhaust ducts under positive pressure, chimneys and vents shall not extend into or pass through ducts or plenums.

That doesn't look applicable and none of the exceptions cover a plumbing line in the duct.

[B] 601.3 Exits.
Equipment and ductwork for exit enclosure ventilation shall comply with one of the following items:

1. Such equipment and ductwork shall be located exterior to the building and shall be directly connected to the exit enclosure by ductwork enclosed in construction as required by the International Building Code for shafts.

That one definitely doesn't look like it applies.


801.8 Abandoned inlet openings.
Abandoned inlet openings in chimneys and vents shall be closed by an approved method.

I don't see it there either.

The closest thing that I see in the code might be to seal around the pipes, but even that is a liberal interpretation of the code.

Thank you very much Marcus.

I probably would not bother commenting on this personally. I'm sure I have seen it before. I don't see galvanic corrosion. I see typical corrosion from not cleaning flux off the pipes. Will not cause pressure drop.

I'd be more concerned about a gas line passing through the return duct or a waste line.

The line was likely run post construction because they could not route it any other way.

I see these installations constantly. I thought there was a code reference that stated return and supply air bays and ducts are to be dedicated just for HVAC and not to route and install other systems.

That copper water pipe through a return air duct? That is a non-issue in my book.

Couldn't you find anything bigger to whine about?

Originally Posted by John Kogel

That copper water pipe through a return air duct? That is a non-issue in my book.

Couldn't you find anything bigger to whine about?

The house was otherwise perfect

I still haven't seen anything in the code that addresses this, so while I mention it as a non standard installation, I don't think it's a big deal either.

That type of installation is pretty common around here in 50's houses when they use joist bays as returns. I have never found anything that does not allow it.

Some have pointed out the possible condensation that may occur with type of installation. Here I have never seen that as an issue with it.

I also see wiring passing through which is allowed by exception for cable passes through the space perpendicular to the vertical run.

This is from NEC 300.22
Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.