I'm headed off to my sister's north of KC MO this Wednesday, so the issue of the fresh water tank freezing was again on my mind. Since she doesn't have a spare bedroom, I stay in the coach over the holidays. Temps this weekend are going to be near single digits.

Last December, even with the heat pad on, the tank eventually froze. I decided then to figure a way to minimize the chances of that happening.

The first choice was about 12' of tubing to run hot water from the kitchen faucet into the tank drain. This would have to be hooked up every time, and a window opened to allow the connection.

Then it occurred to me - I had to replace the city water connector a few years ago, and it was under the sink. So was the kitchen faucet hot water line! Off to the RV place for a couple of tees and 12" flex, on to Home Despot for a valve, and a half hour later I can pipe hot water into the FW tank with just a twist of the handle!

KOOL idea (maybe I should have said HOT idea!

We seldom go to the freezing areas but this is a good mod for the future.

Thanks for sharing!!

This will also make kitchen hot water available without running any down the drain until it gets hot. Handy when boondocking.

Good point - hadn't thought of that, but my HW tank is also under the sink, so I get hot water instantly anyway. The shower, on the other side of the coach, is a different story - so I fill the dogs' water bowl while I await the hot.

Notice how I cleverly labelled the hot water line so's I wouldn't cut the wrong one.

I did notice that there are 4 90° ells in the tank fill in about an 18" run...and the fill line is 3/8". No wonder it takes so long to fill the tank...

quote:

Originally posted by Rusty:
Good point - hadn't thought of that, but my HW tank is also under the sink, so I get hot water instantly anyway. The shower, on the other side of the coach, is a different story - so I fill the dogs' water bowl while I await the hot.

LOL...Ours is just the opposite, with the water heater next to the shower and far from the kitchen sink.

quote:

No wonder it takes so long to fill the tank...

I think there is some plot to frustrate RVers filling their tanks. I have never had one that filled will. Either gravity or pressure had some sort of glitch.

Since we live on sunny Vancouver Island, frozen water tanks aren't a common occurrence. I would however like to know the mechanics of what you're trying to do with the hot water tapped into the tank fill line. Will this hot water be circulating into the tank constantly or just for a period of time that you reach in and turn valve on and off? This seems like an awkward place for a person to have access to on a regular basis. My wife stores lots of stuff under sink and it would be a pain to reach the valve without some real contortions. Also trying to remember to turn hot water tap on probably wouldn't work with my memory. Did you give some thought to wiring 110v into the insulated fw tank compartment with a switched light bulb to ward off the cold temps? Or even run it with a timer if its doesn't have to be on all the time.

I store a lot of stuff under the sink, too - so I located the valve near the top of the compartment so it's within easy reach. With the valve, I can dump the entire HW tank into the FW tank, or just crack it to allow a constant flow.

I considered several options, including strapping a 120VAC heating pad (for muscle aches) to the bottom of the tank. I used a 75W light bulb last year, and it didn't work - there's no room for it in the FW tank compartment, and placing one underneath didn't transfer enough heat (it was constantly windy).

This arrangement allows me to control the process; I intend to crack the valve, circulating hot water into the tank constantly. Both the circulation and the heat contribution from the HW heater should keep things thawed. The HW tank can produce far more heat than a heating pad or other device.

Underway, the HW tank captures engine heat, so I can let 'er rip, either by fully opening or cracking the valve. The insulation on the FW tank isn't too bad, but last year, with the temps around 5°F at night and never above 30°F in the daytime, the tank eventually froze.

Rusty,

Good to see you using the old noggin.

One thing to remember is that hot water freezes quicker than cold. Something to do with the oxygen level in the water. Therefore once you begin, you're committed!

My water heater of choice is to stay firmly planted in Florida for the winter, but I did think of a clever way that might work. How about installing one of those 110V aquarium heaters in a tank epoxied adjacent to the water tank. You fill the open topped heater tank up when needed and it will heat the water to a set level and transfer heat into the adjacent potable water tank? When not needed, simply drain and let sit.

Just an idea. I'm sure there are also commercial systems out there just for this too.

Corey



th

quote:

Originally posted by noble97monarch:
Rusty,

Good to see you using the old noggin.

One thing to remember is that hot water freezes quicker than cold. Something to do with the oxygen level in the water. Therefore once you begin, you're committed!

This is a fable, born in the old days when the non-frost-free freezer had a shelf with the cold plate in it. A layer of ice would build up and effectively insulate the cold plate from the ice cube tray. The hot water would melt the ice and allow better heat transfer, and thus might freeze faster. Hot water has less oxygen content.

quote:

How about installing one of those 110V aquarium heaters in a tank epoxied adjacent to the water tank. You fill the open topped heater tank up when needed and it will heat the water to a set level and transfer heat into the adjacent potable water tank? When not needed, simply drain and let sit

Just an idea. I'm sure there are also commercial systems out there just for this too.

Corey

That's a creative idea, however, aquarium heaters are only a few watts, and there's no place to put another tank under my coach.

Does hot water freeze faster than cold water?

Does really hot water freeze faster than lukewarm water?

etc, etc.

It's not simple. Scientific American Had an interesting article a while back.

Rusty, do you sleep with the furnace on? How about sending a little heat to the water tank bay? Would that be practical?

A little farther out.........RV gas furnaces are horrific heat wasters. How about running the furnace exhaust through a heat exchanger made of some copper or brass tube submerged in the water tank? Of course, this would depend on proximity of furnace to water tank.

If that causes too much back pressure, a bilge blower might be fun to try. Air flow and heat loss would make it an interesting project. Another way to go would be for a little aquarium pump could run water through some tubing exposed to the furnace exhaust heat. Simplest might be to wrap it around the exhaust pipe and then insulate it. Better would be tubing of a small heat exchanger in the exhaust flow path. Like a small motorcycle oil cooler or a power steering fluid cooler. Some of this would depend on how long the exhaust duct is. The pump could be wired to run only when the furnace was running.

We don't go out colder than the teens, so cheap vodka works for us.

The FW tank is virtually inaccessible, enclosed in a sheetmetal tomb between frame rails. The advantage of the system I set up is simplicity itsownself and the fact it can run on electricity (300W element, much more than a heating pad or aquarium heater), propane, or engine heat when underway (when airflow increases heat loss) means it can be used anytime, anywhere.

In addition to the heat applied, merely moving the water around lessens the susceptibility to freezing.

I think you should be able to get a tank heater from a Ranch/Farm supply store. They'd certainly have a heater made for plastic water tanks and it would be higher powered for the type of use we need as opposed to a fish tank heater.

I would have preferred that, but there's no access to the tank - I had to repair the split fitting on the tank for the drain - and there was barely room to work. Also, tank heaters are 120VAC, meaning I'd need to hard wire it and run the genset underway.

quote:

We don't go out colder than the teens, so cheap vodka works for us. Smiler

Bill, Life is too short to drink cheap booze

Nick