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!
Solid Foundation Home Inspections, LLC