Idea for simplified water tank heating -- need your advice

[profdant139]

This stems from a brilliant project posted by SteveAE over on the boondocking forum, to keep the tank from freezing. His project involved a solenoid that controlled the flow of hot water into the outlet pipe of the tank.

My idea is much more crude (and much easier for the non-technical person). Imagine a tee coming off the hot water line that runs to the sink. Imagine a hand-controlled valve at that tee. From the tee, run a line to the cold water intake filler pipe, which is just a gravity feed tube down to the tank.

In the late evening on a cold night, turn on the water heater (if it is not already on). Once the water is hot, open the valve at the tee and run several gallons of hot water into the fresh water tank. (The tank should be insulated -- I have reflectix over it, but I think I will add more insulation.)

This crude solution warms the tank. The downside is that it is a one-shot deal before bedtime -- nobody is going to get up and do this in the middle of the night. Steve's solution is temperature-controlled -- no human needs to lift a finger.

So that is my question -- what do you think of this amateurish work-around? I wanted to get your thoughts, both pro and con, before I cut into my water lines!

Obviously, this is not going to work for sub-zero temps -- the tank will freeze no matter what. But we have discovered that our water lines don't freeze in the 20 degree range, although they will freeze at 11 degrees. Please don't ask how I discovered this threshold.

I look forward to your comments!

(By the way, this is for boondocking -- if we had hookups, I would just install heat tape and be done with it.)

[Jacksons]

wanderingbob wrote:
Water that has been boiled will freeze quicker as a lot of oxygen bubbled out , not much , most high school chem class will show !

but your water heater doesn't bring water up to the boiling point, if it does, you have a problem

[mobeewan]

Acampingwewillgo wrote:
Just a thought also...I know my water heater has a pressure release valve on the same side of the MH as the water fill....just wondering if you could use that as your source of Hot water for mixing?

You shouldn't be messing with the relief valve. It is there for a specific job, not for a source of hot water or to aid in draining the tank. Sediment in the tank winds up in the sink faucet aerators and slows the flow resulting in the aerators needing to be cleaned periodically (the white and sandy looking sediment). You could get some of the same sediment caught in the relief valve seat causing it to drip. There are a lot of posts here about both dripping relief valves and using them to flush and drain the water heater. I doubt all the dripping relief valves are due to loosing the air bubble in the top of the water hater. It's a safety relief valve not a globe valve.

[profdant139]

Tucquala, I had never heard of a running tee, but I have now -- thanks!

[wanderingbob]

Water that has been boiled will freeze quicker as a lot of oxygen bubbled out , not much , most high school chem class will show !

[TUCQUALA]

Consider running the hose to a tee in the FW tank vent line. Then you would not have to go outside as I see it!!! Should work ok esp if you use a running tee, one that would have an angle to one leg pointing toward the tank. Just turn on your new valve, and send the hot water down the vent tube.

[profdant139]

Acamping, I thought about the pressure valve -- run a hose from that to the fill pipe -- but that would mean I would have to go outside in the freezing cold to push down the little lever, right before bedtime. Brrrr. Maybe I could rig up a little stick to push the lever with, from inside . . . . 😉

[Acampingwewillg]

Just a thought also...I know my water heater has a pressure release valve on the same side of the MH as the water fill....just wondering if you could use that as your source of Hot water for mixing?

[WyoTraveler]

DrewE wrote:

WyoTraveler wrote:
How about the theory that cooling hot water freezes quicker than cooling cold water?

It's wrong. If you think it over, you'll realize that before it becomes frozen water, the hot water has to first become cold water...at which point it takes as long to freeze as cold water.

Likewise, hot water comes to a boil sooner than cold water, for exactly the same reason.

Gordon three post covered it very well. But for your information it is called the Mpemba effect dicovered in 1963

[DrewE]

WyoTraveler wrote:
How about the theory that cooling hot water freezes quicker than cooling cold water?

It's wrong. If you think it over, you'll realize that before it becomes frozen water, the hot water has to first become cold water...at which point it takes as long to freeze as cold water.

Likewise, hot water comes to a boil sooner than cold water, for exactly the same reason.

[profdant139]

I really like SmKettner's idea -- hook up to the faucet and run an ordinary hose into the fill pipe! The only trick is how to get the hose from the faucet inside the trailer into the fill pipe, which is outside.

Hmmm. I have a connection for an outside shower, which I do not use (and have disconnected). I wonder if I could use that as the source of the hot water, since the source is already outside?? I could simply run a hose from the outside shower faucet to the water fill pipe -- very simple.

But that would probably mean that I would have to go outside just around bedtime to turn on the hot water, and then go back out there to turn it off a few minutes later. In 15 degree weather. Possible, but not wonderful.

So back to the idea of running a pipe from the faucet to the fill pipe -- I guess the tee into the fill pipe would have to be inside the trailer.

Keep those ideas coming!!

[pianotuna]

That manual valve would be nice when boondocking to preheat the water lines--so there would be less waste water. Go for it!

[GordonThree]

WyoTraveler wrote:
How about the theory that cooling hot water freezes quicker than cooling cold water?

that is true for systems where evaporation helps to cool the water faster than just conduction and radiation losses. as hot vapor leaves the surface of the water, it takes heat with it... so hot water in the ice cube tray freezes faster than cold, but only a little.

rv plumbing system is a closed loop more or less, I guess you would have some evap in the holding tank, but OP states the tank is insulated, so the heat would be retained in the air inside the tank and not lost from the system completely.

[coolmom42]

WyoTraveler wrote:
How about the theory that cooling hot water freezes quicker than cooling cold water?

That theory has been proven to be bogus.

It is true that hot water initially loses heat faster than cold water, because the rate of heat loss depends on the temperature differential between the water and its surroundings. BUT the hot water still has much more total heat to lose before it gets down to the same temp as its surroundings, so it is less likely than the cold water to freeze in the same amount of time.

I think this is a good simple idea and wouldn't cost much to try out.

The lines & pump will be full of warm water. Plus the warm water in the tank will radiate some heat into the area of the pump uptake line. If you could wrap Reflectix all around the tank & uptake line, that would be helpful. (I'm assuming you are talking about an exterior tank with an uptake line to the pump inside the trailer.)

[time2roll]

Should work fine. Could let the water heater cycle a few times to prepare for a very cold night.
No shortage of propane right?

Could just get a hose adapter for a faucet and run the water direct to the normal fill point. $6 or less for proof of concept.

http://www.homedepot.com/s/faucet+to+hose+adapter?NCNI-5