that's too bad. I have a 3ht high pressure and 2-2ht's, hey, maybe I can put them together and make a 4ht. I run my heaters from a portable 20lb tank. It's a bit of a hassle compared to a belly tank but serves me well for the most part. I have the tank inside the van, which some people say is illegal, but not really. People are allowed to take their bbq tanks to be filled and transport them in their car. I transport mine in my truck, disconnected, with the valve turned off. When operating, the doors are wide open so even if their was excessive venting, there could be no explosion. I have used propane for over 30 years and if used with a little common sense, it poses no serious safety risk. I would like to try a hx but it's been a little complicated for me to build myself. I am working on it. I don't want excessive by-pass to my recovery tank and am undecided on automatic heat diverters. I need to see some other systems first. The 3ht gives me all the heat I can use right now and I can turn it up to a 1000psi for tile and grout.