LEAK UNDER BATHROOM SINK

[Montana_2387]

We have a 2002 Montana 5th wheel and have discovered a leak under the sink in the bathroom. We know the two pipes obviously go to the hot and cold water. But, there are two other pipes to the right of them that look like they have a vent on top. There is water leaking out of the top somehow. Any ideas on how-to fix this?
Also does anyone know of a way to cover the skylight over the shower. It felt really good in Washington, but now that we're in Bakersfield, CA IT'S HOT...will appreciate any help on either matter

[8.1al]

Those lines are for your blackwater tank flush and the thing on top is a vacuum breaker which is supposed to keep water from the tank from siphoning back into your hose. It can also make a big mess when it malfunctions. You can replace the valve or as some members have done
(1) Just remove valve and hook two lines together or
(2) Do the above and then add a shutoff valve somewhere so that you are sure the water doesn't drain back