TheSamba.com :: View topic - Hot water heaters--anybody done it?

Tue Mar 02, 2010 9:51 am

I've seen hot water heaters made by coiling copper tubing for coolant through a tank of water, then attaching a pump to the faucet, etc. However, I don't like the idea of that coolant flowing through a coil in my drinking water...what if years down the road it develops a leak and isn't noticed?

You can see these done quite nicely on syncro.org and other places. It does work, no question.

What about the reverse--having drinking water flow through a copper tube that's wrapped around a coolant hose (or even header pipe)? Then if the copper leaks, you lose your drinking water but don't end up with contaminated water.

If anybody's done this, do you need a pump or would gravity do the work?

Seems like a nice mod, what a luxury!

Another idea, wrap the flue for the fridge in copper coils for a heat exchanger, then you'd have hot water anytime the fridge is on...

Tue Mar 02, 2010 10:04 am

I have seen something like this done.

http://www.goenergystead.com/URLrewrite.asp?404;ht...directed=Y

Tue Mar 02, 2010 10:12 am

copper tube will last a LONG TIME in a vehicle heat applicaiton, and as long as your fittings are outside the holding tank there's very little chance of any failure & contamination.

the problem I can see is the engine coolant is regularly above boiling point and can conceivably raise the holding tank water temps to boiling.(add in elevations?) and you'll get steam and a BIG HEAT SINK inside all day/night.. might be nice for winter camping use, but for summer the added heat wouldn't be welcomed.

I have seen a custom DIY insulated water tank under the back seat that had coolant piping thru it, and some temp regulator to maintain it's temp @ a desired & safe lvl.

Tue Mar 02, 2010 10:22 am

Alaric.H wrote: I have seen something like this done.

http://www.goenergystead.com/URLrewrite.asp?404;ht...directed=Y

That thing is awesome, I think $120 is a great deal too...If you could set that up somewhere clean it would make a great outside shower

Tue Mar 02, 2010 10:34 am

keep in mind that heater requires an external water supply

here is one installed in the back closet of a westy, plumbed to the drinking water tank
http://www.thesamba.com/vw/forum/viewtopic.php?p=4057487&highlight=shower#4057487

Tue Mar 02, 2010 10:35 am

Alaric.H wrote: I have seen something like this done.

http://www.goenergystead.com/URLrewrite.asp?404;ht...directed=Y

Methinks that one looks extremely cool . . er, hot.
I think I saw that unit installed inside the rear driver side cabinet in Wild Bill's syncro at Mogfest NW last year. Open the hatch, grab the shower head, instant hot water shower.

(I prefer the low tech and free method of a few holes drilled into the lid of a pop bottle and then filling the bottle with stove heated water for doing dishes and shower, but that's just me.)

Tue Mar 02, 2010 11:22 am

I kind of like this one - if I wanted one at all that is - I like that it doesn't need "city water pressure" to operate. Easy enough to hook it up to your "propane tree" and run it off a 20lb tank.
having said that however, I really don't want to carry more "stuff" - I'm happy heating wash up water on the stove and as for showers - well some campgrounds have them, other times there's a lake - whatever..

http://www.walmart.com/ip/Hot-Water-on-Demand-Port...ku=8187723

Tue Mar 02, 2010 11:28 am

Check out spitsnrovers site for some DIY ingenuity. He uses both thermostatically controlled engine heat while underway and residual heat from the Dometic while camped. Pretty clever I think - and he includes a parts list. Hopefully he'll chime in later, but check out his site for detailed info.

See the 'Hot Shower' and 'Fridge Water Heater' links.

http://www.griffco.ca/interest/vw/vwmods.htm

Tue Mar 02, 2010 12:25 pm

Already some good posts on the subject. It looks like the easy way to go is with the propane on-demand units, though they aren't made to be permanently installed and of course use propane.

I'm thinking for a heat-transfer type installation, the way to go would be to wrap the dometic flue with copper tubing, etc. This would not only provide hot water but decrease the amount of heat behind the fridge, especially if you were to wrap the flue/tubing in insulation (like exhaust wrap for example.) That evil heat behind the fridge would transfer to the water and to the outside. And you'd have hot water all the time, maybe not enough to shower with but for the dishes anyway.

The other problem with the shower is getting the GF to use it...maybe just stick to the washing dishes idea...

Tue Mar 02, 2010 1:08 pm

There's no way copper tubing on the flue for the fridge will provide enough heat to get hot water. I size heat exchangers for a living. You might get 1-2 degrees of rise under those conditions if you're VERY lucky, not the 60 degrees you'll need to make hot water.

Robbing heat from your flue will also cause the flue gasses to cool and condense moisture inside the vent. Not something you want to be doing.

Don't waste your effort. Look for a propane solution.

Tue Mar 02, 2010 1:37 pm

Good advice from an expert. Thanks. It does seem the idea of wrapping a coolant hose with copper tube would work, though, no? Cost-wise the whole thing would be cheap too.

Tue Mar 02, 2010 1:56 pm

You could make a copper coil heat exchanger to sit on the stove and use the burner as a heat source, but by then you might as well just heat a pot of water. The Fridge burner just doesn't have a big enough flame to produce enough heat.