I've lived in this 4 year old house since it was built. This summer, I noticed periodically a horrible sewer smell coming from the floor drain in the basement, which was remedied by pouring water down it. The frequency that this procedure has to happen is intensifying - to now, where I have to pour 2 gallons of water every two days to keep the smell from returning. I live near the bottom of a hill, have not asked any neighbors if they're experiencing similar problems - there is a lot of construction going on in our area. Is there any method to solve this permanently or at least less often and could it be associated with the large addition going in behind me - such as too many houses on the sewer line, so it's backing up, or drying out, or what?? I've had a plumber look at it, and he says for some reason that water in the trap is fluctuating up and down quite a bit but he doesn't understand why.

 

It sounds like your floor drain isnt
vented properly,you are exceding 1 inch
of water colum. this means that by code the water in a trap should not rise more than
an inch to maintain a positive reliable seal.
When a toilet is flushed the water washes down the line pushing air along in front of it,when it passes by the trap,instead of
the positive pressure being releived thru
sucking air off a vent that should be between
the trap and where the line ties to the sewer main it attempts to pull air thru the trap causing the water level to rise and fall.this will rapidly syphon the water
below the trap seal allowing sewer gas to
enter.you may also install a back water valve on the main sewer line where it
exits the house,this will prevent the
back flow of sewage and sewer gas from
entering the house,I beleive you did
mention that your house is at the bottom of a
hill,which is a good reason to have a back water valve if you do not already.
I hope that bit of info helps,if you need
more,just write back and ill answer.Robert

 

the back water valve is installed on
the portion of the sewer that exits
outside the house,about the first three
feet or so,but if the sewer is over
3 feet deep it makes it hard to service
the unit.My other thought is maybe a small
hairline crack in the bottom of the trap
allowing the water to seep out.I have encountered this in the past in cast iron
and pcv.Not being there makes it difficult
but I think you are describing the problem
pretty accurately.If you do not use the
plumbing and the trap still drains down
a crack is very likley,also It sounds like
the trap is vented by the amount of movement
you are getting with the water.One last
possibility that I do not encounter very
often is,if a mop string is laying in the
bottom of the trap and extending up and into
the drain line it will act as a wick and
draw the water out of the trap.(capillary
attraction).just a possibility.
Robert