Septic smell from washing machine


Chip C

Sorry for the toppost, Google's follow-up is confused today.

(e-mail address removed) asked:
We are getting a septic smell from the washing machine drain (which is
in the wall of the main floor).
It's the only place in the house we get this.
Could this be due to the water blasting through the trap with too much
force? If so, how do we rectify it?
I suspect, as you do, that the force of the washer pumpout is
siphoning water out of the trap - assuming there *is* a trap!

The quick and easy fix is to keep jug of water handy to manually
refill the trap after each time the washer runs. If this doesn't fix
it, then maybe there is no trap in this drain, or the trap was made
wrong; I'm told that a trap needs a horizontal section after it, and
that traps that go straight into vertical drops are not effective,
though I don't understand why (more prone to siphoning, mebbe?).

You should investigate to see if this drain is properly vented, which
is also important in preventing siphoning. (If the trap or vent are
very wrong, it might be that flushing the upstairs toilet is siphoning
the trap or pushing fumes out it.)

Finally, make sure there's an "air gap" where the washer hose enters
the drain. Basically this means the hose has to fit loosely into the
drain, it shouldn't fill the drain. This is mostly to prevent
back-suction into the washer (ick).

Good luck,

Chip C


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