Negative angle trap arm issue

Hi all,

I was inspecting an older house the other day and noticed the old concrete slop sink in the basement had a proper p-trap, but the 20" trap arm was at a negative angle (pitched toward the p-trap).

I know that this is normally a write-up, but the long term homeowner was over-hearing the conversation with my client and said:
“Water only goes down that drain every month or more. I purposely installed the trap arm that way so there is more water in the drain to ensure that the trap seal doesn’t evaporate, and cause sewer gas to potentially back up the drain.”

I thought he had a valid point. Which is worse, a negative angle trap arm or having to remember to keep the trap primed to avoid sewer gas back-up?

I’d appreciate your thoughts!

Ron Lind
Solid Foundation Home Inspections, LLC

Sounds like a valid explaination to me. I would not the reverse slope and the explaination and let the new owner decide what to do now that he has all the information.

Yes…I would note it as well as the new homeowner may use that sink more than once per month…eh?

Who cares why it’s wrong? It’s wrong, regardless of how good the “explanation” was.

I rarely take into consideration any comments from the seller unless it points me toward additional defects. . .

after you point out the error, it’s up to the potential home owner to decide. they may use it everyday when they move in. i’d also suggest having it fixed, and if they don’t use for a long time, pour a cup of vegtable oil down the drain. that keeps the water from evaporating, and won’t hurt the drain. we do it all the time up here to close up a camp for winter, or an R.V/ camper. work very well. veggi oil doesn’t evaporate.