No flow from hot water tank Nautilus P1 system

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No hot water

Our 2017 27RL Reflection 5th wheel has the Nautilus p1 water distribution system. Once last year and then again a few days ago after filling the fresh water tank we had absolutely no hot water. For clarity I will say the water in the tank is very hot and our problem is we have no flow. This problem starts out with a slow flow and then progresses to absolutely no flow at all fixtures including the outside shower nozzle. So I know the water is hot. This problem occurs when we are on a city water connection or on the fresh water onboard tank. I bought this RV new and have filled and winterized the plumbing several years so feel confident I'm not doing something wrong when filling up and preparing for a trip.

The only way I can get the hot water tank to provide water is to shut off the pump or city water valve, release pressure on the system by opening a faucet, drain the hot water tank by removing the drain plug outside. Then refill the tank. As the tank is refilling I have a hot water valve open somewhere to release the air as the tank fills. When a steady stream of water is observed I then shut off that valve and consider the hot water tank properly filled and ready for use.

It seems things are fine until next time we prepare for a trip and I experience no flow again from the hot water tank! In troubleshooting today I have suddenly realized that if I turn the RED HANDLE sideways (allowing water to go to hot water fixtures without going to the tank first) I have a flow.....not hot of course....but a flow. Then when I turn the handle back to UP I notice a gurgle sound then I have water flow from the tank!! In looking on the Internet I have found some information about the Nautilus system and something about a Vacuum breaker/ check valve somewhere but I can't seem to locate it or determine exactly what it does. I can see the check valve on the output port of the tank and it's not hard to remove.

Now my thinking is that a check valve on the hot water tank output connection is hanging up and not allowing flow. Does this make sense??? Appreciate any help or advice to solve this problem. Leaving for a 3 week trip!! Wife expects hot showers while we are on the road.

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Awesome thanks for coming back and telling us you found it. Over the years I've read about a lot of check valves failing and the spring goes down the PEX tube and lodges at the first bend. If water keeps flowing I wouldn't worry about it. But if it's not flowing I would start looking there.

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UPDATE ON PROBLEM.......  The check valve on the outlet port of the hot water tank has failed.  The spring is missing and presumably rusted and now probably inside the tank.   When the spring is missing the plunger on the check valve will block flow from the tank preventing any hot water supply.   Easy fix and available at Amazon. 

[opnspaces]

That's weird that it starts working if you relieve the pressure in the system and then restore the pressure. The question is whether the problem is at the red handle or at the water heater check valve. Here's what I would try.

Turn off the water heater so you are not dealing with hot water.  Do whatever it takes to get the system in the broken state. Now with either the water pump on or with city water hooked up open up the water heater access door. Find the Temperature and Pressure Relief valve at the top of the tank and flip up the handle.  If water comes spurting out with a good flow the red handle is working and the check valve is faulty.