Sorry I have not been around much. The backflow valve is right under the cover the 2" pipe ties into. This cover needs to be opened and the flapper serviced every year to ensure proper operation. The open pipe is an over flow tee, which is on the house side of the backflow valve. When the city sewer backs up and closes the flapper your water usage from the house over flows from the tee into the pump pit. The pump then pumps this water into the closed side of the valve. During the yearly service check to ensure the pump is working properly as well.