The device you are filming is your backflow valve. Internal parts have gotten old and need to be replaced. I would not recomend you do this work yourself. Find a licensed plumber in your area and have them fix it. On the valve will be a tag...get this info ready so the plumber will only have to make one trip. Give the plumber the numbers and he should show up with the rebuild kit. BTW, the small valves pointing up should all be in the off position. That black tubing (i believe) is being used as a flush valve for something else. When you open that valve before the black fitting and tubing what happens?

Good luck,
Tom