Thread: In this house we obey the laws of thermodynamics

Originally Posted by RedShirtGuy

I don't suppose anyone knows how high hot water will rise above cold water? I'm guessing "all the way" but here's my situation...

I have a "spare" chiminea on my bush block that I thought I'd make a water jacket for (or just coil copper pipe around connected to a tank) so I can have a separate hot water system. While the chiminea would be on the ground, I would like to have the main reservoir on the roof (+3m) so that it can gravity feed into sink faucets and a shower.

Any forseeable problems with getting the water up to that height purely by heating it? Also, any problems with getting the cold water back down to warm it back up? (it would be a purely gravity/physics base recirc system).

Normally I'd run my own tests etc but at the risk of wasting a bunch of dollars on unnecessary piping I though it would be prudent to ask first

RSG

You may find that the pipe diameter is critical to minimise frictional losses. When you use natural circulation (as opposed to forced by pump) the pipe size should normally be larger. A friend just building his house and using evacuated tubes used either 5/8" or 3/4" pipe. When I built a house years back we used 1" pipe. Make sure you get a continuous rise in the pipework to avoid airlocks. I would also consider insulating the hot pipes in particular.

Regards
Paul

Take note of what Paul says about continuous rise in the piping to the hot water storage tank
and the need for insulation.

I can't offer any advice on pipe size but a plumber mate of mine always said he could
push water forever with the use of heat.

If the level of your supply tank is the same as the hot water storage tank you won't have any trouble at all.

This may be relevant.....Our rocket stove water heater: 2.5 years on « Milkwood: homesteading skills for city & country

Thanks for the diameter tip Paul. I probably would have used smaller. I should probably do a bit more reading on that part.

I figured eventually I would have had the whole lot insulated. The reservoir is a small old Rheem thingy that I was going to tweak so it's already pretty good.

Love that rocket stove heater Chris. It's always good to see projects like that revisited to find out how well they've worked and survived. It's all fine and dandy to make something in the first place, but if it doesn't withstand the test of time there's not much point.