In some cold weather installations where the drainage sump pump pumps the water out to grade (your yard) or into an open site drain like your gutter or down spouts a plumber or installer may not use a check valve due to the possibility of the discharge line freezing the trapped water in the pipe during the winter. Even with the possibility of freezing there are some drainage installations that incorporate horizontal discharge pipes where you would want a check valve installed to prevent the lengthy discharge pipe from siphoning back into your basin after the pump shuts off.
We suggest consulting a licenced plumber or foundation specialist familiar with local plumbing codes when routing or connecting your sump pump discharge line. We also suggest that when you replace your sump or sewage pump you also replace the check valve, flappers have been known to break at the hinge and if your pump has failed, your check valve is soon to follow.
If you have a lengthy discharge pipe system we recommend a ball valve to be installed above the check valve to isolate the long column of water when servicing the check valve or the pump. There are some check valves that screw right into the discharge of the sump pump. If you use this type keep in mind that you will have the whole column of water to deal with when you change or services this pump. We also suggest using a separate check valve and ball valve for any two pump (duplex) system. This prevents one pump from back feeding to the other pump.
We also suggest bracing or clamping your pumps discharge pipe securely to the wall or structure to prevent any torque or movement of the pump when it starts or stops. We have heard of poorly installed pump discharge pipes coming apart at the check valve. Again, check you local plumbing codes, some areas do not allow rubber connections in the discharge pipe of any sump or sewage pumps.
Finally, there is a lot of discussion about whether a check valve should be installed horizontally or vertically. This too may be covered in the local plumbing codes. Most check valve manufacturers will emboss arrows on the valve for either method of installation. Some pump manufacturers feel that a check valve installed horizontally will open better if there is a build up of solids, sediment, or waste resting on the flapper. Others feel that the flapper closes better in the vertical position. I personally prefer the vertical installation.
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