Boon Docking, run out of water, burn up the HWH ?

[marjoa]

Our fresh water tank sensors don't work.
Tried many methods to clean tank and get sensors to work with no results.
I'm not replacing them with new expensive 3rd party sensors.

We have an Atwood, Motoraid, 6 gal., elec. & LP HWH.
Our habit using the HWH is we only turn on the HWH ON when we need it and then turn it OFF.

So with that out of the way...
When we fill our fresh water tank to boon dock, and then eventually run out of water, will there still be water left in the HWH or will it drain that out too?

I'm concerned about turning on the HWH while boon docking and then after several days, we run out of water, or very low on water and don't know it and then burn up the HWH by turning it on and not knowing there's not enough water in it.

Our manual doesn't address this scenario.

[CLIFFTALL]

There will be water in the HW tank if you don’t call for it ( turning on faucet ) when the FW tank is empty. If you call for hot water ( turn on faucet ) when FW tank is empty , the element will burn out.

[aether_one]

Since you are boondocking I assume you are not using the electric element so no, it will not burn out.

When you run out of fresh water when using the hot water you may pump some air into the water heater tank, but you'll never empty it.

When you run out of fresh water, turn off the water heater and you'll be fine.

[azpete]

even if you run the water heater tank empty, it will not be totally empty of water. just below the outlet opening.

there is a high temp shut off that is designed shut the gas valve down when it reaches a preset temperature.
there is also a hi temp eco switch that does the same.
thats not to say that the electric heat elements might not be damaged, but not likely, they are also designed to resist high temps.
its just a good idea to not use it if you are out of water. there is a danger of causing
a fire outside the heater itself.
just use caution, like when using any other gas appliance.

[Steveo57]

Since the water heater is typically at floor level and all the faucets are higher it will always stay full even when you run out water.

[Quincy]

The water pump pushes water into the Hot water tank and when the potable water tank is empty the HWT will still be full as there is no water to push against the water in the HWT.

Hope this helps.

[Domo]

Originally Posted by Clifftall

There will be water in the HW tank if you don’t call for it ( turning on faucet ) when the FW tank is empty. If you call for hot water ( turn on faucet ) when FW tank is empty , the element will burn out.

Nope.

It takes a bit of ingenuity to get all the water out of the HWH and expose the element. For instance, if you remove the water pump and check valve, the water lines could siphon backwards and drain the tank - rare occurence, I would think - plus if someone was doing that kind of work, they'd probably know to turn off the water heater - and lastly - the OP is boondocking, using an inverter or generator to heat their water would be the least efficient method (as stated, they turn it off when not in use - implying they use their LP).

[Old-Biscuit]

Have to have water pressure to push water thru water heater tank

Tank stays full when you run out of water pressure UNTIL drain is opened.

YES...water heater elements WILL burn out within a few minutes if turned on DRY.....that occurs when WH Tank has been drained/element energized
Element will burn out before the normal temp t-stat opens and/or high temp t-stat trips

Propane operation with empty WH Tank (Drained) will heat tank up enough that Normal temp t-stat will open but enough heat sink will occur that the ECO (Energy Cut OFF---High Temp T-stat) will probably trip also.
Usually no harm/no foul situation IF---BIG IF---tank is allowed to naturally cool down. Damage can occur if cold water is valved into tank while still hot---especially if Suburban WH as they are steel GLASS-LINED tanks.


Fire outside of combustion chamber......
That is due to obstruction in combustion/exhaust chamber regardless if WH Tank is full or not.



SO if boondocking and water pump goes 'burruuuup' that means your fresh water tank is empty.

WH will be OK unless you remove drain or on some RVs open the low point drains

[marjoa]

OP here...

Thanks everyone. Very helpful.

[winniman]

If it was that easy to empty the hot water heater, winterizing them would be easier. I am winterizing my rv now. I left the low point drains open over night to drain the lines. The water heater was still right full the next day when I pulled the plug, and opened the blow off valve. Bottom line is, no it will not empty out the water heater by just running the pump, and in my case, draining the fresh water tank and lines either.

[AKIQPilot]

Lots of good answers here. Your water heater will not empty itself or be emptied when your fresh water tank runs out of water. As soon as the water quits going in to the water heater the water also quits coming out.