Plumbing, Cables, Line Set Routed Through Duct

[Robert Foster]

I ran across a return duct today that had a plumbing drain, electrical cables and the heat pumps line set all running through the return air duct. I've never seen this before, but think I know it to be not allowed/incorrect.

Can I please get some explaination/education on why this is not allowed/incorrect so that I can write the "why it's a problem" part of my narrative to best affect.

Thank you.

[Markus Keller]

Plumbing - contamination hazard, any leaks in the drain line can leach bacteria into the system which will be distributed throughout the home and can cause sickness or death
Electrical - since you can't see all the electrical, you can't say whether now or in the future when somebody modifies something that the line won't energize the sheetmetal ... and zap
Freon - contamination hazard
See IRC M1601.4 and M1801.8
Write it up as non-compliant and a safety hazard.

[Rod Butler]

I'd say it is not a problem.

All utilities are exposed in your mechanical room are they not?

Having said that, the installation looks pretty "Harry the Homeowner" ish.

[Robert Foster]

Thank you for the reply Markus.

Rod, I do not see the comparison to the mechanical room as very pertinent. The mechanical room is not under negative air pressure like the return duct, which is drawing everything in the duct, including potential contaminants, into the air handler for relatively quick delivery to all rooms of the house.

[Jerry Peck]

The main difference between that duct and the mechanical room, which could be under negative pressure if the return was open to the room and the room was open to either the return ducts or the environmental air of the house, the main difference is that those items in the environmental air of the mechanical room are not concealed, they are exposed, whereas that duct is closed and concealed and no one would know of a problem causing burning and outgassing of the toxic chemicals of the prohibited items in that duct.

Items which are allowed in the environmental air of mechanical rooms and air handler closets with louvered doors to a hallway (which contains the environmental air) are not allowed in plenum ceilings, ducts or return air plenums (of which a plenum ceiling is one type of return air plenum).