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vik Fri Mar 05, 2021 11:38 am


I'm thinking how to ad bit of comfort to our tents on wheels.
Almost by coincidence I found UK company Surejust and they are making calorifiers with thermostatic mixing valve to get reasonable hot water out of the unit.
I shall not be connected to the cooling system if the water system is empty. I thought about using a valve(s) and put it under the rear westy seat instead of rear heater.

Is this whole concept a good or foolish idea?

DuncanS Fri Mar 05, 2021 11:52 am

Boats have been doing this for years and you don't necessarily need a valve. Usually these hot water heaters are continuously full and replenished by a pressure system for the main water tanks. An insulated tank under the floor with the radiator lines going through it with a copper pipe would heat up 4 or 5 gallons just fine. it would take a few miles, but would work even without a more flow restrictive water to water heat exchanger.

fxr Fri Mar 05, 2021 12:03 pm

Cheaper, easier, and more versatile would be a Zodi water heater (forget their shower attachment, get a better one).
With the ubiquitous 5 gallon bucket which heats up in a few minutes if you re-circulate, this can provide all the hot water you need.

mikemtnbike Fri Mar 05, 2021 12:29 pm

Yeah I've made my own hot water heaters that scavenge heat off wood stoves, been going on since before the combustion engine. This can happen, just a question of figuring out how.

MarkWard Fri Mar 05, 2021 12:34 pm

It would be nice to have hot water, but the problem is how much water it takes to live off the grid. Showering would burn through quite a bit of your supply. We will boil water for dish washing or boil extra water when making coffee, for the warm wash cloth in the am.

But yes, using the engine to heat water in place of the rear heater core would be the easiest thing to do. Post pictures.

Steve M. Fri Mar 05, 2021 12:47 pm

One thing to consider and remember is that a Stop Leak might clog a heat exchanger with small passages.
If you get one like that it might be a good idea to install isolation valves to close it off to keep it separate from the cooling loop in case you need to add some.

spitsnrovers Fri Mar 05, 2021 1:09 pm

Have you seen this DIY job?

JEL91Westy Fri Mar 05, 2021 4:14 pm

Donít want hijack this thread, but wonder if any one has come up with a good way to get hot water from a CDH. Heating the water with the engine is great, but if you arenít driving, and already running a heater, not having to start the van and idle would be ideal. Any thoughts anyone?

fxr Fri Mar 05, 2021 4:42 pm

There's a version of the CDH that will heat water. Best to go to the CDH thread...

jordauto Fri Mar 05, 2021 5:51 pm

I don't know if I have any pics of my set up. But I used an EGR cooler off of an ALH 1.9TDI as found in 98-2003ish Golf and Jetta models. It's mounted by the engine (which is a Subaru 2.2) and the main heater feed hose runs through the part that coolant normally goes through. My fresh water shower pump feeds the water through the passages where the exhaust gas went in the Jetta. Its a well made stainless steel water to water heat exchanger. I mounted in vertically in the engine bay and the fresh water input comes from a quick coupler under the bumper. The fresh water side is completely self draining by gravity so it can never freeze and break causing a coolant leak on that side of the heat exchanger. I use a 12 volt plug in pump and shower head from Amazon. With the engine at operating temperature the water heats up enough in a single pass to take 4c water from a creek and have a hot shower standing in the snow. I vary the temperature of the water by adjusting the flow. Less flow = hotter water. An anti scald valve or mixer would make it more user friendly though.

vino de vano Fri Mar 05, 2021 7:58 pm

My home made heat exchanger, inspired buy Natcho.
Copper has gone up, so its not cheep to build these days. I deleted my rear heater so its plumbed into the front heater loop, I also have a heater bypass loop for summer when the front heater is closed off.

Steve M. Sat Mar 06, 2021 6:58 am

Later model cars have enough oil coolers on them that you should be able to find one you can use as a heat exchanger for shower water after you flush them out adequately to water use.
For example the Volvo V60 has one measuring about 4-5" x 2".
A drawback is that they have small passages and will seal if you put a stop leak in the cooling system so best to ad isolating valves to close it off from the cooling system if you ad a stop leak.

DuncanS Sat Mar 06, 2021 8:54 am

VanWine--Yours is perfect. Is that 3/8ths tubing you wound around a mandril? With some foam insulation and fiberglass to protect it you would have even more efficiency. If you insulate the hot water line going out, you will also have a thermosyphon which will heat the tank without even drawing from it. Or a small 12v boat pump could circulate it and only run while the engine is running and not cause an unwanted electrical load.

MarkWard Sat Mar 06, 2021 9:36 am

vino de vano wrote: My home made heat exchanger, inspired buy Natcho.
Copper has gone up, so its not cheep to build these days. I deleted my rear heater so its plumbed into the front heater loop, I also have a heater bypass loop for summer when the front heater is closed off.

Nice execution.

jimf909 Sat Mar 06, 2021 9:39 am


jimf909 Sat Mar 06, 2021 9:47 am

Here's one of the latest, most complete examples of this. They talked about selling these as a kit.

It seems the water would be cold a few hours after turning the engine off so this never appealed to me.

Similar to the Zodi, I use a propane fueled on-demand hot water heater.

Californio Sat Mar 06, 2021 10:43 am

If you still have your trusty Dometic, you could accomplish the same thing by wrapping the copper tubing around the exhaust and then plumbing to wherever. Since it's so close, a tank under the sink would be easy.

The advantage to this would be that you'd have hot water even when the engine was cold, as long as the Dometic pilot was lighted.

vik Sat Mar 06, 2021 11:15 am

Thank you for feedback.

I did not decided to go with the project so far. But I do like the idea.
As for water capacity - do have 80l fresh water tank under floor.
As for hot water is only when driving - I'm ok with it. We do generally travel every day. If we stay longer it is mostly a camp site with showers.

Due to the lockdown I can not get to the workshop at the moment. Can someone be so kind and measure the westy rear seat (for 2 persons) if the 10l will fit there?
Length 575mm
Width 240mm
Height 245mm

I would prefer under floor unit. Will look on that option as well. What I do like on this product is that it contains the mixing valve as well as it is isolated and will contain the heat for reasonable amount of time.

MarkWard Sat Mar 06, 2021 11:52 am

Looks like someone has made a still before. :wink:

Abscate Sat Mar 06, 2021 11:54 am

All that kit instead of a Zodi? Crazy

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