From the Suburban Water Heater Manual Page #6
http://techsupport.pdxrvwholesale.co...ser-Manual.pdf
WATER WEEPING OR DRIPPING FROM PRESSURE RELIEF VALVE
One way to reduce the frequency of this occurrence is to maintain an air pocket at the top of the water heater tank. This air pocket will form in the tank by design. However, it will be reduced over time by the everyday use of your water heater. To replenish this air pocket:
I. Turn off water heater.
2. Turn off cold water supply line.
3. Open a faucet in the RV.
4. Pull out on the handle of the Pressure Relief (P 8 T) Valve and allow water to flow from the valve until it stops.
5. Release handle on P 8 T Valve - it should snap closed.
6. Close faucet and turn on cold water supply; as the tank fills, the air pocket will develop.