Triangle Tube has added an 80-gallon tank to its line of Phase III residential indirect fired water heaters. Triangle Tube's "tank-in-tank" design is now available from 20 to 80 gallons residentially, and up to 119 gallons for commercial applications. The new HL-80 features a first-hour recovery of 435 gph and a 10-minute dump load of 133 gallons. Triangle Tube.