We have a 2015 179. We boondock almost all of the time, thus we never use the water heater-neither electric nor propane. since we bought it used in 2017, we have never had water in the water heater or hot water lines.

Every time that I winterize,I have drained the whole system and find water under pressure when I open the hot water low point drains(2 of them).  this has happened several times.

I have 3 valves closed that serve the hot water function-the inlet to the heater, the outlet from the heater and the crossover line between the inlet/outlet line.

https://postimg.cc/bGhFb471">

I have opened the pressure relief vale-no water and no pressure.  I have removed the anode rod and no water.

so how is water getting into the hot line and become pressurized??

I have tried to figure this out and it remains a puzzle. I would appreciate any ideas.

Thanks in advance.

travel safe and often

Vann

I think that what is happening is that when you use a faucet, if it isn't turned so just the cold water is on, some water is leaking back through the faucet valve into the hot water lines.  The fact that there is no water in the water heater tank I think helps to validate that this is probably what is happening.

thanks Stephen

Your theory makes sense- we do have a single lever faucet in the kitchen. When I turn it to the left nothing comes out as there is no water in the hot lines. that could be moving cold water into the hot line.

 

However, I also have the hot water valve turned off under the sink. so it seems unlikely that cold water would be backing up into the hot water pipe past a  hot supply shut off valve when it is off.

 The 3rd valve between the water heater inlet and outlet pipes is turned off as well although that is not visible in the picture.

The sink faucet in the bath has 2 separate knobs for hot/cold, so I don't think that would create a crossover from the cold line to the hot line.

The amount of water that comes out from the low point drain is small-maybe a cup, so it's really inconsequential.  But it is a puzzle trying to figure out how it got in the hot water line and was pressurized.

Thanks for your thoughts.

Travel safe and often

Vann

Even a tiny leak in that middle bypass valve would produce a cup of water in the hot water lines given a few months. That's what id suspect is the cause. 

Next time you dewinterize, with your 3 water heater valves off as you normally use your trailer   try opening some hot taps open and see if anything comes out. You'll have to wait awhile. 

You could also try leaving the hot line low point drains open and running the cold lines at each fixture. If water comes out that would prove StephenHs theory. 

Thanks for more ideas and input.

I will add that we do not have an outside shower and the inside shower hose/shower head have been removed-so that eliminates 2 potential issues.

most likely is Offgrid's idea-correct as usual. I installed a 1/4 turn shut off valve in the hot line under the kitchen sink and it is closed .

I will try to remember to open the hot valves next time we de-winterize and see if there is any appreciable amount of water in the lines after use.

I do use compressed air for winterizing -particularly since we do it multiple times a year.  Being in NC, we are still using the Pod off and on during cold weather. We just returned from 5 days at Cape Hatteras and the temps were below freezing part of the time.

thanks again for the ideas.

Travel often and safe

Vann