check valve on sump pump

[jocar]

I have a sump in the basement with a pedestal style pump in it that works a lot when it rains hard, it does not have a check valve on it. What are the consequences of not having a check valve on the pump and is it installed right at the base of the pump before the rest of the discharge piping. Could somebody post a diagram how it should be installed because I also heard you have to drill a small hole somewhere in the piping. Thanks in advance.
Joe.

 

[Caduceus]

This should give you a good general idea of an installation.
Depending on the pump, a relief hole may need to be drilled in the pipe. Instructions should come with the pump as to whether or not it necessary, what size hole and depth below sump pit lid.
Typically the hole would be drilled below the check valve, under the pit lid, but above the max water level of the pit when the pump kicks on. Some pumps may already have a relief built into the pumps body.