Hot water

2006 travel supreme, ...just starting a trip and no hot water at the spigots,shower anyehere! The tank is heating, i have opened the relief valve at the top of valve and cycled the bypass valve, no help. When i first turn the hot water on at the sinks i have water come out but then slows to a trickle and stops after several seconds. Any help would be nice. Seems like a valve is cracked but not opening all the way. But which one???