Where to get Copper Coil for hot water compost thingy ?

We are running a Summer Permaculture Garden Program here in Las Vegas for 3 weeks for 42 kids & I want to display to them how we can get hot water (to wash dishes) out of a compost heap. Anyone know where to buy the parts online ? I could not find them in hardware stores locally. The camp starts next week & I just got approval to do this a few days ago. Any help would be greatly appreciated !!

Also, we are outfitting this school to be as Sustainable as possible as it is already the model school & many people tour it in order to decide how to build their own school garden & to witness the kind of exciting things they can be doing to not just become more sustainable but to save lotsa money !! So I am also looking for options as far as companies who sell the best Rainwater barrels or tanks. (the slope or pitch of this school makes rainwater catchment so exciting !!) I have one but don't know alot about them & we are having a huge party/fundraiser in a few months but we want the school to be fully stocked with all the latest greatest Permaculture methods in order to make this school THE example for all schools in Las Vegas. We already have a flatbed garden that uses less water than a raised bed (in the desert we have crazy evaporation rates) .. it even needed its own valve as it was getting flooded being watered at the same rate as the raised beds. And now we are building a sunken bed with Ollas (buried clay pots) & Hugel Kulture. Which I hope to irrigate using nothing but rain water ala the Brad Lancaster method or rain water catchment. So my ultimate goal is to water as many gardens as I can with rainwater alone in the desert. (the square footage of the roofs is immense ) Which would be pretty impressive as most people here don't even know you can grow food in the desert !!

We made a Cob Bench (with 25 kids & their parents) in the shape of a large caterpillar (thanks to my wife who is an artist) so the kids could sit n learn in their outdoor classroom.

We have the support of the #1 non-profit, Green Our Planet, who has helped to get funding for this, the 2nd fastest school garden program in the nation with soon to be 77 schools with gardens. And Permaculture is finding its way into the mix. In fact, at the School Garden conference we recently held I could not believe how many times I heard "Permaculture" uttered in people's presentations !! It is really catching on here & many great people are getting behind it.

So if anyone has any ideas which would be great to display at a school (can't do fire ... yet - so no Rocket Stoves) any help would be greatly appreciated !! Thank you for your time & have a great day !!

I think this is the photo you were trying to post.

If you want copper, it is usually sold as refrigeration line. Local HVAC supply should be able to get you a roll. But it will cost you, copper is a precious metal these days. Home brewing supplies also use copper or stainless coils as wort chillers, easy to adapt as a small heater. Amazon can get you either option overnight if you are desperate.

The cheap answer is black plastic or pex water line, but it is plastic. I am ok with plastic if it isn't disposable and in this situation it will probably last longer than copper-but I understand if you aren't.

If it's just for the dishes then thin copper brake line tubing would be fine. It's cheap and should last a good 20+ yrs. Black poly pipe would be good for the run to and from the compost heap but isn't very conductive so won't exchange heat as well as copper - which is a plus for the run from the heap but a minus for using in the heap. However it will still work fine for your purposes I guess as you don't need maximum efficiency?

Thank you Burra Maluca !! CAn you tell me how to do that if it's not too much trouble ? I would like to post more pictures ...

Thank you R. Scott !! I did look on amazon but I didn't know what it was called .. I never thought of refrigeration .. that's it !! Thanks so much !

Thanks Stever Farmer !! The cheaper the better as I am coming out of pocket for this ... but it'll be worth it if we can convert this school & get all the others to fall in line which is the master plan !

The video Paul posted says 1/2 inch Poly pipe .. which they coil thru out the pile ... it was my idea to buy the kind which is already coiled & use copper as it conducts better ... I'll look into 1/2 inch poly