Originally Posted by massplumber2008
Hey RJ:
Does the backwater valve look like my picture at all..? If so this is a valve that was used for years that let water from ground water flow out to city sewer....that would be why you did not see water movement when flushing water...it is separate from the main drain, but attaches into it after this backwater valve. If water is standing in pit, try to push on internal flapper (see pic) or pull mud away from entrace for water (as in pic.). This one is also missing its cap.
If this is not it...let me know. I can tell you that any backwater valve should have a cap,and water should not be standing in pit...something up...OK? Mark