Freshwater in water heater -available?


On descriptions of freshwater tanks/capabilities, some posters talk about their rigs having X, plus six gallons in the water heater.
How available is that? Don't you need water in the FW tank supplying the pump to push it out?
I know it could be drained out of the TC, caught, and used if necessary, but, not really accessible through normal system use, right? Do some TCs have a valve that releases HW back into the FW tank? Aren't they typically at the same low height?
Just curious if this is "Salesman" talk/euphemism that has been adopted by owners?

School me, please....
Upon first fill up of the season (assuming it was all flushed out) it will take that 6 gallons from the freshwater supply. It doesn't drain back and is only used as it's replenished by "cold" water being pumped in. So, throughout the season, when you fill the freshwater tank, you would have that capacity plus the 6 gallons in the heater tank.


Yes, I understand all that, but if your FW tank is empty.....
The HW tank water is not readily available through normal systems use..... Right?

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I believe you are correct. Never thought about it but it would need FW to be pumped in to displace anything in it. No FW to pump in, no water out of the tank. There is a drain port you could use, typically for winterizing.


"Just curious if this is "Salesman" talk/euphemism that has been adopted by owners?"

Yes it is. That 6 gallons is weight you have to carry, but it really can't be used. The drain dumps it into the dirty bottom of the compartment and then out onto your shoes.

Some mfgrs claim X gallons of fresh water, but that includes the 6 gallons in the heater. So they really have (X minus 6) gallons that can be used.


Yes my hot water tank is 5 gallons that I can't readily access, but I have two water tanks at 75 gallons each so that is no big deal. In essence we can only access 97% of our water capacity.
Our case is extreme as we have huge capacities, I just want to point to the fact that hot water tanks have their place in expedition trucks and even vans but maybe not jeeps.


I'm not knocking hot water heaters. They are a good thing.
The water inside is freshwater, but is not readily available.
Just interesting that salespeople and some owners breezily infer that it is usable.
It is, just not normal systems......

And.... Wow, that is a LOT of onboard water!
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SoCal Tom

A properly installed RV water heater should drain at a low point when vented. Usually this is accomplished by opening a water valve with the pump off. It can be readily available if you want it to be.

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I replace my normal drain plug with a brass adapter that has a screw off cap. Mostly it makes it very easy to drain the hot tank. I just unscrew it with my hand. I have 65 gal fresh tank. I could very easily get the last 6 gal out if I wanted. Emergency use I suppose. When the fresh tank is empty it's tome to move on.