Make sure you have bled the air out of hot water supply before you light the water heater...do this by opening ht ehot water faucet after turning on the pump. If you have a Wolf Pup 16FB, the access hole to open/close the hot water heater bypass is located under the mattress on left side of bed toward the read. Mine had about a 5-6" access hole in the bed board to reach the hot water heater bypass valves....also..instruction in your manual.
My hot water heater has small leak in the the plug to left and down from pilot assembly.
Hope this helps...what is your model of Wolf Pup?