Running pure water through old radiators painted black? Black hose pipe's to catch the sun? Free energy from the engine block?Running pure through solar panels?
You are bonkers, and have clouded a sensible disscusion with marginal alternative therapy type hogwash.
My conclusions from this thread are.
An lpg on demand system is the superior method with lower capitol and running costs and better results.
An lpg conversion may be necessary.
An outside flue is reqiured.
Any installation must be done by a corgi qualified engineer.
Running almost pure water through radiators painted black or through solar water panels and then through DI bottles into your insulated static storage tank which can be transfered into your van mount is not mad.
How do you think people with swimming pools heat them up? Certainly not with a diesel or LPG heater as they would end up penniless and skint.
I suggested a few good ideas which I use myself in the summer to make the most use of the sun and after initial set up costs (i.e. some cheap solar water panels, or paint some radiators black, or a very long length of black hose left in the sun and connect it after your RO but before your DI bottles) it's a DIY route that others on here can use affordably without any running costs involved.
You can slag me off all you want as it doesn't offend me as I like a chuckle but my van mount tank contains warmish water (during the summer) from transfering water from my static tank so I don't need to heat my water as much to get to the desired temperature that you would need to using your heater.
Mr Solubility I look forward to your next constructive critism