I don't believe I can asnwer your question difinitively but on the whole I don't believe one should be necessary. The real issue is, how far underground is the storm sewer relative to the basement floor. And, how absorbant is the soil plus what severe rainfall might be received? Where we reside, we have both ejector pits and sump pits. Sanitary sewers are elevated above the basement floor level and any waste water produced in the basement must be pumped into the sewer. This is the ejector. Groundwater is collected from around the outside foundation and emptied into a sump pit located in a corner of the basement. This water is pumped outside onto the lawn. I suspect it is this water which your builder says will not be an issue. Our soil here is primarily clay so will not retain much groundwater. Hope that helps but don't be afraid to speak with your community permit department for their input.

I think "Need" is the operative word. Chicagoland has more strick codes, I think mainly because of Ms. O'Leary's cow kicking over the lantern and burning the city to the ground. You can always ask your local Building inspector. If you haven't had water problems in the past, I would not worry, you can buy a portable utility pump just in case, you can screw a garden hose onto the pump and pump water out if needed. Dan Martyn

I've installed battery operated back-up sump pumps on the same discharge line as the primary sump pump. It's a separate unit but comes with a checkvalve to permit the single discharge line. They're available from Lowes, HD, Tractor Supply, Wal-mart, etc. The only thing that didn't come with the pump was the battery. They recommended a marine, deep discharge, battery, but I've found an automotive battery to do well enough, at a much lower cost, in most cases (i.e. power back on in a day or three).

Regardless of disposer or not, drain waste from a sink cannot be dumped into a sump pit. Even if only adding a sink, a proper waste water receptor must be used that is vented & discharged into sewer outlet. If you are only using the sink for grey water, sometimes a sink mounted laundry tray pump is used but not recommended. Should you want garbage disposer, than a sewage ejector is used that is capable of handling small solids.