Thanks Mike, I will show your response to Ron. We got the drip leg. I don't know if Ron noticed the adapter. The air handler next to the water heater was sucking alot of air, full of dust at the unsealed seams. On another note: The one inch clearance for the B vent to combustibles. Does the ASTM standard consider drywall a combustible? NONCOMBUSTIBLE BUILDING MATERIAL. A material which meets either of the following requirements: 1. Materials which pass the test procedure set forth in ASTM E 136. 2. Materials having a structural base of noncombustible materials as defined in 1, with a surfacing not more than 1/8 inch (3.17 mm) thick which has a flamespread rating not greater than 50 when tested in accordance with ASTM E 84. The term noncombustible does not apply to the flamespread characteristics of interior finish or trim materials. A material shall not be classed as noncombustible which is subject to increase in combustibility or flamespread rating beyond the limits herein established through the effects of age, moisture or