We have a ranch style house with a basement and overhead sewer. The
house wastes (bathroom and kitchen) drain by gravity into the sewer
lateral which is about 6 feet above the basement floor.

There's a sump in the basement laundry room that receives water from
the drain tile surrounding the house.

The laundry sinks and the washing machine drain into a basin under the
basement floor. That basin drains into the sump. When the sump fills
to a certain level the pump automatically pumps the sump's contents up
to the sewer lateral.

My wife complains that sometimes the sump has an offensive odor. I
can't smell it because by olfactary apparatus isn't top shape, but
visitors have said that from time to time they've smelled the odor,
too.

We tried just running fresh water into the laundry tubs to sort of
flush the basin and the sump, but that didn't help.

I dimly recall someone else having had this problem and someone
suggested that bleach or some other chemical added to the sump now and
then might help by destroying bacteria or other nasties growing in
there.

The water column in the sump is about 5 feet deep and roughly 30
inches in diameter. If my high school geometry is holding me in good
stead, that's about 24 cu. ft.

So what chemical, and how much might be a good dose for my smelly
sump?

All suggestions welcome.

-Len