Check valve first time for everything?????

I have been in the mechanical work force for over forty years now and this is the first time I have observed a check valve in a drain line.

This line has a stand pipe and P-trap on the other side of a concrete wall in a full basement. I think I understand why it was placed in this position, to prevent sewer from backing up and coming out of the standpipe as it is the lowest open drain in this system. Makes me think this home has had past blockage in the main drain line. I guess I am going to have to check the IRC mechanical as I have never ran into this before just a shade tree plumber.

I did discharge water down this drain and the check valve did open and the washing machine has been in use as the home was occupied. What say YOU

Makes sense, if your supposition is correct. At any rate, I don’t know of anything wrong with it. Let’s see what others say…

If there are homes at ahigher elevation on the same city sewer line this check valve prevents backup into the home in the event of main line blockages down stream of the home. I had a 4" sub slab check valve in a home I owned that was on hill with a dozen homes or so higher than mine was. The backwater/check valve was required by the city.

Mike; we are flat landers here this town is flatter than the bottom of a cast iron skillet:)
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Oh well then. Nevermind:)

I prefer the rolling hills of western Wisconsin.

http://www.gandygallery.com/art/Masters/Bougie/Images/St_Croix_Valley_Oct.htm

Check out IRC Section P3008 Backwater Valves.