The 5 wrap pipe is really good at heating the ground. When it comes to the underground insulated pipe, you get exactly what you pay for. The foam filled pipes have proven itself over decades of use. All the TOP OWB companies all recommend using one of the approved foam filled pipes. Top OWB companies and quality underground supply lines go hand in hand for a reason. There is a reason, those multi wrap pipes are not labeled or give any ASTM specifications. They make alot of claims but thats all they are. Usually they come in non oxygen barrier or very small inside diameter sizes, less than 1". When you read alot of the horror story threads on replacing the underground pipes, its this stuff along with the good ole bubble wrap style as well. Seems if that product was as good as its claimed to be, why wouldn't the foam companies use it as well, since its less than half the price and easier to make. Since many times the pipe is as much as the boiler, you'd think they would give their customers another option, unless it doesn't really work and they don't want their name on it.
I have been told the 325g is not a true gasification unit and doesn't meet new or current standards. Has problems maintaining temp and consistent burn. Maybe thats why there is a "good deal" on them. 2nd hand info, so take it for what its not worth. Seems like a good company, but hard to tell since they haven't been around as long as some other OWB companies. Tough business, seems you either love it or you don't, and of course every NEW owner loves them, you have to see 6-10 years down the road and see what they say.
