Atwood (90029 Mixing Valve for XT Water Heater The Atwood XT 10- Gallon water heater provides the equivalence of a 16- Gallon unit without increasing the space required Saves weight while fitting in the same cut-out dimensions of other Atwood water heaters Comes pre-configured with a winterization bypass kit, tee fittings, hoses and a thermostatically-controlled mixing valve with check valves in both inlets 10 Gallon Water Heater, XT Exothermal, (Mixing Valve for XT Water Heater)