Can water heater fill from fresh water tank?

[phann]

We are about to take the maiden cruise with our 2015 Flying Cloud. I know the water heater fills when hooked to city water system. But does it also fill from the fresh water tank when boondocking?

[Silverflames]

Yes the water pump should push water into it. To test it, unhook from city water, turn on your pump, turn on the hot water heater, and open your hot water tap in one of the sinks.

[AnnArborBob]

Originally Posted by Silverflames

Yes the water pump should push water into it. To test it, unhook from city water, turn on your pump, turn on the hot water heater, and open your hot water tap in one of the sinks.

But first make sure that you have some water in the fresh water holding tank!

In all seriousness, I would not turn on the heater until you have verified that the hot water tank is actually full of water. Simply turning on the hot water tap in the bathroom or kitchen sink and let the hot water tank fill up (i.e., purge itself of air) and then when you see water flowing with only the hot tap on, you know the hot water tank is full and you can then turn it on safely.

[TG Twinkie]

Make sure you are not in the BYPASS mode for winterizing. In the BYPASS MODE You will still get water out of the hot water tap. But it won't be going thru the water heater.


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[CBWELL]

To make sure that you have water in the HWT, open the relief valve when filling the first time. When water comes out, pop it closed and you are good to go.

[phann]

Thank you all. You are so much clearer than the manuals !!

[Cottrell1951]

In 2015 30' Flying Cloud, will opening the the low point hot water drain empty the Atwood hot water tank or is the 1/2" plug removal the only way to empty it.

[idroba]

Originally Posted by Cottrell1951

In 2015 30' Flying Cloud, will opening the the low point hot water drain empty the Atwood hot water tank or is the 1/2" plug removal the only way to empty it.

Since the hot water comes off the TOP of the water heater, the low point hot water drain will not drain the tank at all. You may get some of the water out via the cold water drain, but due to a lot of reasons it is unlikely you will get the tank fully drained that way. The plug removal at the bottom of the water heater tank on the exterior is the only real way to drain it fully and be sure it is done.

BTW, Airstream "low point drains" seldom really drain the water out without compressed air.

[TG Twinkie]

Replace the plug with a boiler cock or similar device. Problem solved.


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[Skater]

To (hopefully) clarify it further: It's the exact same water system, with two sources. Your house has one source of water, most likely the city water or a well pump. An RV water system has two sources, the city water connection and the fresh water tank (via the pump). They both connect to the same cold water system, which feeds the water heater.

Water under pressure doesn't care where it enters the cold water piping, it'll go wherever it can.

[jerry1939]

PROBLEM SOLVED, NEW QUESTION PUZZELING
I had a problem with hot water on my 1993 31' Excella which I recently purchased. At first I was getting only luke warm water at the taps. My first thought was the thermostat and ECO so I replaced them yesterday. I tested the system again today and still only luke warm water. Was puzzled and thought I would try the water temp. at the tank by opening the HW relief valve. Sure enough the water was very hot. I then knew it had to be a valve. I went back to the hot water valves under the sink (There are 3) one for hot (output) and one for cold (input) The third was puzzling as it looked like it was a connection between the hot and cold. It was open so I closed it and then WOW! the faucets operated properly and my problem solved. My question now is: Why is that 3rd valve there and what purpose does it serve. ???
Jerry 1939

[dznf0g]

That's part of the heater bypass for winterizing. Open the center one, close both of the others, and no antifreeze gets into the heater while winterizing.

[Too tall]

Arrg. I dewinterized at camp and saw drip drip from above the two low point drain petcocks. Stopped everything I was doing. Turned off city water. Opened the sink spigot and cracked both low point valves....than googled . This thread fixed me. I was unaware I needed air headspace in the HW heater. My mistake was that after dewinterizing I used the pressure relief valve to get rid of antifeeeze foaming. Doing so, apparently, cause the hw heater to fill with no headsapce.

All good now.

All praise the patient women and men who patiently answer here.

[Adventure.AS]

Originally Posted by Too tall

Arrg. I dewinterized ... My mistake was that after dewinterizing I used the pressure relief valve to get rid of antifeeeze foaming. Doing so, apparently, cause the hw heater to fill with no headsapce.

When you winterize next time it is best to bypass the water heater and drain it. When de-winterizing purge the lines of any RV anti-freeze before opening the bypass to the HWT. It wasn't clear if you winterized by putting RV anti-freeze in the HWT but if so, it is a waste of antifreeze and not that good for the heater.

[Too tall]

Originally Posted by Adventure.AS

When you winterize next time it is best to bypass the water heater and drain it. When de-winterizing purge the lines of any RV anti-freeze before opening the bypass to the HWT. It wasn't clear if you winterized by putting RV anti-freeze in the HWT but if so, it is a waste of antifreeze and not that good for the heater.

Grab the brass ring. Not putting the HW heater into bypass before I purged the lines was one of two mistakes. Using the pressure relief valve to flush the tank was the second and the worst. I had to remove the drain plug, re-install...refill and that fixed it.

-J