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We have an odor problem only when the windows are
open. It is similar to the odor associated with propane.
We do not use natural gas or propane, and there are no
gas lines in the area. None of our neighbors have a
similar problem. We have sealed the basement twice on
the floor and once on the walls and have capped the
sewer vent. The odor dissipates when the windows are
closed and begins again when they are open. We are
totally baffled. -- Sandy , Maine
Your question is not a unique one. The odor you associate with
propane
is often described as skunk oil. It usually consists of methyl or ethyl
mercaptan, compounds with a sulfur odor. Some of the mercaptans
smell like rotting cabbage. They don't quite smell like hydrogen sulfide,
another sulfur gas that is produced in huge quantities in sewer gas.
The fact that you don't use natural gas/propane nor have natural gas
lines
in the area would rule out this possibility. Since the odor is not
experienced by other houses in your neighborhood, it has to be
associated with your house.
I suspect that the source is in fact associated with the wastewater lines
in
your home. Since the odor is not quite sewage-like, it is doubtful that
any of sewage lines that serve toilet bowls are contributing to the
problem.
The problem is likely to be associated with waste lines from your
washing machine or sink. "Sewer gas" odors in this case tend to smell
like sour dishwater; depending on the kind of soap/detergents/fabric
softeners, etc. that you use the sour dishwater odor may in fact have a
slightly sweet smell. I suspect that both your washer and source of
odor
are in the basement (given the efforts you have focused on your
basement).
This reminds me of a problem we recently experienced in our vacation
home recently. We had one of those unpleasant but not quite sewer gas
odors. It really began to be a problem one evening when we had the
fireplace going (evenings are often cool in northern Michigan, even in
mid-June as they are in Maine) and the windows cracked. The odor
just
poured out even though we had done two loads of laundry early in the
day and the drain trap should have been full. The next morning I filled
the trap and the odor disappeared immediately.
The problem was caused by an open connection to a garage closet
where we intend to put a water softener some day. So much air was
going through the vent pipe that it was drying out the trap in a matter of
hours (rather than the days or weeks that is normal).
You indicate that when windows are closed the odor dissipates. This is
consistent with changes in pressure that occur when windows are
opened or closed. As the windows are closed, the house becomes
more
neutrally pressurized; when opened there may under a strongly negative
pressure condition which causes gases to flow from a portion of your
waste line system back into your house.
If one has a good "sniffer", one can locate where in the house the odor
is
strongest and even its pattern of movement. Try this when the odor
problem occurs again.
Actually, a short- term solution is to pour several glasses of water into
drain lines that are likely to be the source of the problem. These include
the laundry drain and maybe even the kitchen or utility sinks. Make
sure
that all drains are accounted for and pour water into those that are not
often used.
The problem in my opinion is originating in one of your waste lines.
Capping the sewer vent is not likely to solve your problem. Indeed it is
likely to make it worse. A "good" plumber should be able to help you
to
solve the problem on a permanent basis.
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