no need for tubes...........I got 3 block heaters on my fuel tank...run them off a 2000 watt inverter so they stay on until I unplug them when parked for awhile....got an air operated oil pump with inline filter......go to local restaurants and pump directly from their vat to my fuel tank, inline filter stops all the crud, block heaters go to 250 degrees max if I need them....don't need to purge diesel because my veggie's always hot enough...don't use veggie on metal fuel tanks though, it will react with the metal and get flakes in the system, use plastic tank