We are putting a new bath in our basement. We have an existing sump pit for laundry that is about 18" deep. I don't think it is deep enough for a sewage pump. Do we need to tear it out and put in a sewage pit?

You would need both an existing pit and then a new sewage ejector pit. I am assuming your sewage line exits the home through a wall rather than under the floor, is this correct? Foundation curtain drains and sewage can not be mixed, they go to different terminations.

Like Bob said... you need a separate pit for the sump pump and you need a separate ejector pit for the new bathroom.

The sewage ejector most common in my area is a ZOELLER sewage ejector with a 2" discharge... see picture. You can investigate these systems at www.zoeller.com

The ejector pit will have a lid that must be sealed closed at all times so sewer gasses cannot escape. This system will also require a separate 2" vent that connects to the ejector pit and then it exits out the roof by itself. Here, this 2" vent cannot connect into the plumbing vents... it MUST penentrate the roof by itself... period.

Check out the zoeller 2" ejector system... let us know if you have more questions...

MARK