Model DVR (Oval) Type B Gas Vent Installation Instructions

Refer to Table 1 to determine the height above the roof the vent cap must terminate. A listed Dura-Vent top must be used to terminate the vent. It is locked to the top section of pipe, and gives protection against the entrance of rain, snow, debris, and birds. The vent cap should terminate 2 feet higher than an adjacent building or wall, if it is within 8 feet of the obstruction (3- through 12-inch diameter), or within 10 feet for a 14- through 24-inch diameter.

TABLE 1
ROOF PITCH	MINIMUM HEIGHT *
FLAT TO 7/12	1.0
OVER 7/12 TO 8/12	1.5
OVER 8/12 TO 9/12	2.0
OVER 9/12 TO 10/12	2.5
OVER 10/12 TO 11/12	3.25
OVER 11/12 TO 12/12	4.0
OVER 12/12 TO 14/12	5.0
OVER 14/12 TO 16/12	6.0
OVER 16/12 TO 18/12	7.0
OVER 18/12 TO 20/12	7.5
OVER 20/12 TO 21/12	8.0

GAS VENTING SYSTEMS USING VENT CAPS LISTED BY UNDERWRITERS' MAY TERMINATE IN ACCORDANCE WITH THIS VENT TERMINATION TABLE.

*THIS REQUIREMENT COVERS MOST INSTALLATION

Where the vent passes through the roof, the roof sheathing is cut away to provide a minimum clearance of 1 inch from the vent pipe. Straight lengths of pipe are run up about a foot above the roof. A roof flashing is placed down over the pipe, and adjusted so the flashing fits tightly against the roof, with the vent pipe held in a position maintaining the 1-inch minimum clearance from combustibles. The flashing is then nailed to the roof. A non-hardening mastic may be used around the edges of the flashing base where it meets the roof. Non-hardening mastic is placed around the joint between the flashing and the vertical vent pipe, and the storm collar is then placed over this joint to make a watertight seal. The storm collar serves as a counter-flashing to give additional protection.

A gas vent support or firestop spacer must be provided where the vent passes through the ceiling. The ceiling opening is framed, using the same sized lumber as the existing joists, to fit around the raised edge of the gas vent support, which is pushed up into the ceiling from below. The hanger straps are nailed to the framing using 1 1/2-inch box nails to hold the gas vent support firmly, and the clamp is then tightened around the vent pipe. Firestop spacers must be utilized in multistory buildings at each level where the vent passes through a floor.

Sections of pipe are connected to each other by pushing them firmly together and twisting. Screws are not required. If screws are desired, for 3- to 6-inch diameter pipe, use 1/4-inch sheet metal screws. For larger diameters up through 16 inches, use 3/8-inch sheet metal screws. For 18-inch and greater diameters, use 3/8-inch sheet metal screws. Under no circumstances, penetrate the inner liner with screws.