Heating camper holding tanks

[chrisser]

I've been rebuilding this camper all summer.

It's taken longer than I'd hoped, so it looks like we'll be camping in fall/winter.

It's an older rig with exposed black/grey holding tanks that hang from the frame.


There are electric heating elements available to prevent the tanks from freezing, and they work well, but...they're electric. Electricity isn't always reliable at the best of times.

I already have propane on board, and a spiffy combo LPG/110v electric direct spark ignition water heater, and that gives me hot water from two energy sources.

So, I was thinking, if I hooked in some sort of a heat exchanger with a circulating pump to the water heater, I could heat up some propylene glycol and pump it to some coils fastened to the bottoms of the holding tank and drain pipes before I insulate them all up with a fabbed partial underbelly. I've found some ideas for homebuilt copper heat exchangers on the web, and the plumbing and pumps are likely no problem.

What I'm worried about is the hot water tank is going to be in the high hundreds temperature-wise. Without some sort of thermal regulation, I'll "cook" what's in the tanks and that would be a bad thing!


Appreciate any thoughts on how I might regulate this, and if this whole thing is a looney idea, well let me know that too.

I haven't found anyone selling a system like this on the web, and it seems like an obvious solution to me, so I suspect there's a complication that I'm not seeing.

For what it's worth, there are hot water heaters that have auxiliary heat exchangers so running the engine (on a motorhome) heats the water. This is somewhat of a similar concept.

[NCLee]

Here's a link that may be of help.
Using an RV in Winter (below 0F)
http://www.sankey.ws/rvwinter.html
Some of his solutions may work for you.

RV antifreeze is available at most places that sell camping supplies.

Lee

[Anon001]

I don't know what the zoning and regulations are in your area. But if you can legally dig an outhouse pit, why not dig a pit next to the camper, run the holding tanks directly into it. You could rig up some type of top over it so that you don't have to smell the odors.

That was what I did. I'm also on enough acreage that no one would have seen it anyway. That was for my black water tank. For the grey water, I just ran it out on the ground. You could also run it to an area that needs moisture. I will also say that I didn't have enough grey water for it to be very noticeable.

The first winter, I didn't do that and I had both holding tanks freeze. What I had done prior to that was wait until the black water was almost full. Then I would dig a pit, run my hose to it, empty the tank, then fill the pit back in. I had 2 or 3 "pits" around the back of my camper. lol After the tanks froze the first winter, I realized that I had to do something different.

By the way, I was under the assumption you would be living in it. But, if you aren't living in and you are just camping at times through the winter, ignore my posting. lol
Paul

[chrisser]

By the way, I was under the assumption you would be living in it. But, if you aren't living in and you are just camping at times through the winter, ignore my posting. lol
Paul

I was thinking about it for camping.

However, we do plan on eventually living in it for awhile, so any advice is helpful.

[randallhilton]

If you have the budget, here's one way to keep those tanks warm while not using unnecessary amounts of fuel. It's going to sound odd but once you understand the principle you may like it:

1. Get a D'mand water circulator.
http://www.gothotwater.com/

2. Depending upon the layout of your plumbing, find a spot where you have convenient access to hot AND cold piping. (under the kitchen sink or lavatory, or perhaps even at the water heater if it works out well for you)

3. Put a tee in each line (H & C).

4. Connect a long length of 1/2" PEX water pipe to the tee in the hot water line.

5. (this will be tedious) Fasten a few loops of pex -- like a snake - to the bottom of your tanks. Here's a picture of what I'm talking about:
http://www.solarheatingcanada.com/images/solar-radiant-floor-heating.jpg

The tedious part is getting the coils to stay put. Duct tape might do the job but I don't know - depends upon how clean the tank surface is. (theoretically, you could put the loops on the inside of the tanks but it's very dangerous to run potable water through a sewage tank.) I'll leave that part up to your ingenuity.

I suppose you could wrap a few coils around any exposed dump valve piping if you're really good at it)

6. Complete the piping circuit by connecting to the incoming side of the D'mand pump. The outgoing side of the pump will connect to the cold water tee you installed in step 2.

7. Install a bulb type thermostat - it will have a sensing bulb on the end of a long copper coil. You'll fasten the bulb to the bottom of the tank, between a loop of your water line (or inside the tank itself)

8. Use spray foam insulation to encase the tanks, tubing and t-stat bulb with a couple of inches or so of foam. Note: Try to encapsulate the bottoms and sides of the tanks with the foam - the tops of the tanks should be tight against the bottom of the trailer which will provide some heat for the tanks.

http://www.tigerfoam.com/

9. Connect the t-stat to your D'mand pump (use the instructions to figure out how. . .it's pretty simple).

Adjust your bulb t-stat so that it closes at 32f or there abouts and opens at 40f or so. When the T-stat closes, it will crank up the D'mand circulator. The D'mand circulator will pull hot water from the water heater, through the loops, and back through the cold water piping. As soon as the D'mand circulator senses that the hot water has made it all the way through the circuit and back to the cold side it will shut down.

This way, the system keeps just enough heat on the tanks to keep them from freezing and shuts off before they heat up.

You'll still need 110v for the D'mand circ but it doesn't need a huge amount of amperage so may run ok off a battery/inverter.

ps: i'm not endorsing any particular products - examples were just easier than spelling it all out.

This will probably be the most expensive installation idea you get but in the long run, it will probably save the most fuel.

[cinok]

IMO the best way would be to use rv antifreeze. I am not sure what part of the country u are in and what kind of extremes you will be facing. Also how long do you plan to leave the tanks between empties. Something else to o would be to skirt the trailer with a tarp. Depending on temps the ground temp and the temp of trailer might keep them from freezing.

[NCLee]

I was thinking about it for camping.

However, we do plan on eventually living in it for awhile, so any advice is helpful.

For the time being, if just for once in a while camping, I'd simply winterrise it. Empty the tanks. Use the adapter made for the purpose and blow out the water lines or add RV antifreeze to the system (including pouring some in all the traps and the tiolet.)

Then for a wintertime overnight/weekend trip, don't use the plumbing system. Use the alternatives as if you were tent camping. Far less before/after prep work for the water/waste system. And, you may find that you enjoy a more rustic style of camping as an extension of using a camper.

When you move into it, you'll have many more options. For example, stack bales of hay around the bottom perimeter to insulate the tanks and any water lines that may be in the floor structure.

BTW, I didn't see any references to fresh water. I'm thinking in terms of supplying water to your camper (for camping, not living - that's a different situation) during the winter. There'll be some issues if you plan to use full hookups during freezing weather. May not be applicable for your situation, but I thought I'd mention it as a just in case.

Lee

[keydl]

PEX or copper to radiate to the tanks - heat rises so the bottom is good. Add a 'cover' to keep the air flow away and connect to the floor or belly, 3/4 foam or some thing like that.

Hook the 'radiator' to the waterheater with a small pump and set the water temperature cutoff under 140 F. Put a thermostat near the tank to start the pump above freezeing.

Carry a 12v booster alternater hooked to a small gas engine to keep the house batteries up.

The foam can be 'glued' with foam in a can. Include the drain valves and I would put heat tape in also to have a backup.