We recently had our basement redone,, a new slab poured and new underground
sewer drawings installed.
Traps were installed for all new fixture locations.
The work was completed about 2 months ago.. and more recently.. we have been
smelling sewer gas. It seems to occur primarily when our washing machine is
running. My concern is that we did not install a laundry tub for lack of
room. The washing machine drain empties directly into a pipe that sticks
above the floor 1" , is trapped below the slab,, and runs down into the
sanitary. I'm concerned the pressure of the washing machine is sucking the
vents dry.. any suggestions?
Thankyou in advance.
Sounds more like the water pressure is siphoning the trap dry, vents are
supposed to be dry. Try extending the tube up 2-3 feet from the floor so
that your not pumping water directly into the trap under pressure. Make
sure you have an adequate air gap around the drain tube so that it drains
more by gravity than by the pressure of the washer pump. Verify your trap
is not broken and draining from the bottom after you use it (look inside
with a flashlight, usually you can see the water surface if there is no bend
If the trap is vented properly it will not siphon dry. That said, anything
is possible without actually laying my eyes on the situation itself.
However, if you think it is tied to the washer drain, try this:
When the washer is actually draining, check the area for smell. As soon as
the washer is finished pour a couple of quarts of water slowly down the
drain that is 1" above the floor. Check again for smell.
Let us know if either or both circumstances result in sewer gas smell.
Also, is the sewer effluent discharged via sump pump?
BTW, I always try to put my washer box into a 2 inch p-trap that dumps into
a 2 inch san tee. I vent my washer and use 2 inch and use p-trap, never a
problem and it all fits in wall nicely and can be snaked very easy.
And we would also "normally" expect that the standpipe from the trap would
not be 1" above the floor and would probably tie into a washer box that is
at least 36" above the floor to the flood rim.
My guess is that if someone put the trap below grade that they probably were
not compelled to adhere to neither standard codes or practices.
Did the plumber ever come back and install a standpipe and trap?? I find it
hard to belive the trap would be under the cement in the slab. The
instalation you have described to us here is not complete and or not up to
Truth is.. I was the one who instructed the plumber to put the trap beneath
the slab... I was arguing with him over some other issues and chose this
issue to stand my ground.. now I look back and realize iim going to have a
heck of a time cleaning the thing out.. im considering breaking up the conc
myself and moving the trap to a point above conc.. but I will definitely
follow the advice of extending the pipe to 2' above ground.. perhaps a wider
pipe to ensure that the machine isn't blowing out the trap that is currently
One of the notes above mentioned a "washer box",,, what is that?
Here ya' go.....
Typical residential type box:
Set the top of the box at about 42" and you'll be good to go. This is
designed to go "inside" a wall but I am unsure if that is possible because
it sounds like you have multiple issues going on here.
Although I must admit that I find poetic justice with you predicament. I
guess you know that you got what you deserved, right?
And BTW, back in the 70's we used to commonly put the trap and standpipe on
the inside or outside of the wall and simply use an 1/8 bend (45) at the top
in lieu of the washer box.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.