Likely stormwater drain connections.
Eliminate them. They need to be gone. AND you need to only
have your sewer line connected to a connection higher than grade
level. That way, if there's a backup, you're not replacing furnace,
water heater, etc. If there's a floor drain, this is the time to connect
it to a sump pump, rather than have sewage come in by way of a
basement line if there's a backup. Got a washing machine in the
basement? Use the sump pump for it, too.
Oneway valve? Don't believe it. The flap can be held open by a mop string.
And if there is a backup, and the oneway valve is being closed, when you
flush your commode you know what may show up in the basement.
Better if there's a backup for the liquid to overflow from the manhole
cover at the street, or into someone else's basement.

HorneTD wrote in message
ink.net...
If it is an older home they may be the footer, foundation or floor drains.
--
Tom H