No hot water because of freeze

[bsivley]

This has happened before. So I this point I am looking for prevention in the future. Got up this morning and have plenty of cold water but no hot water. I checked the pressure relief valve and we have hot water in the tank. I have a frozen line either going into or out of the tank. The temps here have been at century lows. The last time I just had to wait until the temp went above freezing. At about 36 I finally saw very slow drips of hot water. I turned on all hot water faucets and in about an hour I had hot water. I am connected to city water and the hose has heat tape so no issues there. My unit is supposed to be heated in the closed undercarriage where the pipes are but evidently something is freezing. I have a 2018 Forest River Sandpiper 379 FLOK.
Any ideas what I can do to keep hot water from freezing.

Thanks

[bikendan]

None of FR's RVs are true 4 season rigs. 3 season at best.
(Except for their trailers for ice fishing)

So extra measures have to be taken to deal with extreme temps like what you're experiencing.

[John Dorsey]

We are surviving extreme cold here in SW Wisconsin. After a week of -15 and colder weather I woke to no water. Turns out I had the covered water hook up warm enough the heated hose wasn't activating. Let it get colder and Shazam water. But looking at your floor plan I wonder where the water line branches. Mine all come seperate out of the front compartment. I installed valves to close off the outdoor kitchen. If it's skirted through a salamander under it to heat the bottom. That usually thaws things out quick.

[bsivley]

I have not been able to find a floor plan for my model that shows the plumbing. I suspect the outdoor kitchen may be an issue and as soon as it warms up some I think I will install a cutoff as well.
Good news is the hot water came back about an hour ago. Just hoping I find a way to keep it from happening again tonight.

[llr]

Can't really help with where but if you had good flow from the pressure relief it is not on the cold side. Start tracing hot lines from every place you can see them. If it is all faucets then it's before the first split.

[Rich5117]

Looked up your unit see that your central water panel is up front and your water heater is near the back. Because of this it could be either hot or cold. You will get pressure from the relief valve as the water heater is still heating and hot water expands causing the pressure.

Are you using your furnace regularly when it is really cold at night? Many people turn on electric heaters and don't run the furnace to save propane, but since the furnace is what heats your underbelly it must be used to heat it. On our previous Wildcat there was one duct to the underbelly, I would say the duct size was maybe equivalent to 5 inches and on ours it was closer to the front of the unit, so it took a bit to get and keep it above freezing. Unfortunately, the down side side is, the heated air going to your underbelly might not be making to where it needs to go to heat all the pipes, as there are all kinds of obstacles it has to get past.

On occasion we did have to place a small personal heater in our front compartment. We had a remote temp sensor there and a few times it got really close to freezing in that compartment as well.

[PenJoe]

The hot water heater is keeping the water in the tank warm, so the pressure relief valve is not an indicator. The HWH compartment is the most likely place to look for a frozen pipe. Might try heating that area with DW's hair drier or heat gun if you have one. The most likely would be the feed into the heater because heat from the HWH on the demand side will radiate up the pipes.

[llr]

If you have good flow from the pressure relief valve it is a good indicator. If you barely crack it an get a little water it means nothing.
Good flow the source is good, little to no flow the source is bad.
This is with all faucets closed as they will connect the hot and cold together.

[5picker]

I guess without knowing exactly how much water you let run from the pop-off/relief valve, we really can't say whether it is a supply side/inlet problem or a demand side/outlet problem.

As mentioned, the water in the tank will get hot enough (without supply pressure) to force some water from the tank's relief valve when opened (think expansion) although it wouldn't be a strong steady stream.

If in fact, it was a strong steady stream, you can rule out the supply/inlet (cold) side.

You've still got some investigative work to do.
Best of luck.

[drelec]

If you can leave grey sewer valve open, let hot water faucet trickle in to sink. Moving water will prevent freezing.