Watts Series LL100XL Temperature and Pressure Relief ValveCSA Rated. Standard Models are self closing T&P Relief Valves for Water Heaters up to 105,000 BTU Hr. Watts Series LL100XL has extended inlet shanks for use with the new generation of water heaters containing extra thick insulation. These valves eliminate the use of an extension nipple required with standard shank length models. The combined 2 in 1 Temperature & Pressure relief valve provides the least expensive and proven means for protection against