Rose Pinder wrote:Polypipe HDPE is rated to 120C (that's above boiling), and is what I've assumed is being used in Australasian examples of compost hot water systems. Not sure how that differs from PEX though.
Dean Howard wrote:
CPVC may work, but I'd need information from someone more knowledgeable than me on that.
CPVC is able to withstand temperatures to 180F, and that makes it good for hot water, but a solar collector like you are showing could get much, much hotter. It's also brittle, meaning it will crack along it's length when frozen.
PEX can expand a number of times before breaking from freezing or fatigue (maybe 20 times). Neither is made for solar applications, though you may get by if the system isn't running near the breaking point.
Black poly tubing frequently used for drip irrigation is what is commonly used in the Frenchman's (Jean Paine? Payne?) compost pile heater...with temperatures getting no where near what you might expect from a roof-top solar unit. There is a good reason they use copper and other metal tubes, with anti-freeze, for a heat exchanger. They get very, berry, very, berry hot!
Becky Proske wrote:
Luiz Eduardo Piá de Andrade wrote:...But what about water logging and anaerobic conditions?
"Subsoiling" the area around the trees might also be something to try. The aim of subsoiling is to create pockets in the soil to allow deeper infilitration of air (and water). Repeated over time (once or twice a year) it could help create deeper topsoil. It can be done with an impliment (which does not till or turn soil) or perhaps even by hand with a broadfork.