Our new house has an unnecessary sump pit that I would like to fill in. The pit was previously used to drain the basement stairwell that used to be exterior to the house. However, a three season room was added that encloses the basement stairs and therefore the drain and sump are no longer needed. I would like to fill it for two reasons, 1. The sump smells musty and is contributing to a musty smell in the basement that also permeates into the stairwell through the drain pipe when when the door is closed. 2. When buying the house, we discovered there was radon present and a mitigation system was installed. This unused sump seems to be a route for radon gas into the basement when the lid is off and into the three season room through the drain pipe when the lid is on. The lid fits somewhat tightly and is made of wood.

Can I simply fill the hole and pipe with concrete? What type of concrete would be best? Do I need to use some sort of gravel or dirt to fill most of it and then concrete a thinner layer? The pit is 11inx11in and 18inches deep. The concrete goes down the full 18 inches and the bottom is dirt. The drain pipe is about 2inch diameter and a run of 24 inches.

The basement is dry. There is no sump pump.

Thanks!

 

About two inches down on two opposing sides (at least) drill a couple of holes in the sides with a masonry bit so you can insert short pieces of rebar or big stainless steel nails part way in. This will tie the patch to the slab so it doesn't settle or rise. Or you could even just partially drive in a couple of masonry nails since it might be tight to get a drill in there (but it's ok if holes are angled).

Fill it with coarse crushed stone to about 4" below the top. Compact the stone well as you fill the hole. Cover the gravel with a couple layers of heavy plastic. Use general purpose bag concrete mix with aggregate. One 60 Lb bag will be more than enough. Mix and pour the concrete and after the surface water disappears, trowel it flush.