The company's eF Series™ line of water heaters has now grown to seven models with the addition of one 100-gal and three 60-gal units. All eF Series™ models feature thermal efficiency ratings as high as 99.1% and offer installing contractors the ability to vent unbalanced the equivalent of up to 120 ft utilizing 3-in. ABS, PVC, or CPVC piping or 170 ft using 4-in. ABS, PVC, or CPVC piping.