18-12HT is the 18-inch nominal straight double-wall snap-lock pipe section in the IHP 12HT chimney system. The current Superior WRT4536, WRT4542 and WRT4550 installation manual lists this exact part. Its installed height gain is 16-5/8 inches; use that gain, rather than the nominal section length, when planning the chimney.
| Part number | 18-12HT |
|---|---|
| System | 12HT |
| Nominal section length | 18 inches |
| Installed height gain | 16-5/8 inches |
| Verified fireplace family | Superior WRT4536 / WRT4542 / WRT4550 |
This is one pipe section, not a complete chimney kit. The fireplace installation requires the listed chimney, appropriate termination and all route-specific supports, firestops, flashing and other specified components. Quantity depends on the installation. The WRT4500 manual permits the listed 12DM or 12HT system and requires HT components for Canadian installations. Do not treat this part as a universal chimney for gas, pellet, oil or other appliances; verify the exact appliance listing before ordering.
For the WRT4500 family, maintain 2 inches of clearance from the outer chimney surface to combustible construction. Minimum chimney height is 16 feet for a straight system or one elbow set and 22 feet with two elbow sets; maximum height is 50 feet, measured from the fireplace base to the termination flue outlet. A vertical chimney supported only by the fireplace must not exceed 20 feet. Offsets, support intervals and the selected termination must comply with the installation drawings.
Have the complete system selected and installed according to the exact fireplace manual and applicable codes. Do not substitute unlisted parts or mix systems without explicit manufacturer approval. Superior WRT4536/WRT4542/WRT4550 installation and operation manual, Rev P October 2025 provides the height-gain chart and exact accessory list.
Request a return within 30 calendar days after delivery for eligible new, unused, unassembled and uninstalled items in original packaging. Written authorization is required. Read the Returns Policy for conditions, fees and exclusions.
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18-12HT is the 18-inch nominal straight double-wall snap-lock pipe section in the IHP 12HT chimney system. The current Superior WRT4536, WRT4542 and WRT4550 installation manual lists this exact part. Its installed height gain is 16-5/8 inches; use that gain, rather than the nominal section length, when planning the chimney.
| Part number | 18-12HT |
|---|---|
| System | 12HT |
| Nominal section length | 18 inches |
| Installed height gain | 16-5/8 inches |
| Verified fireplace family | Superior WRT4536 / WRT4542 / WRT4550 |
This is one pipe section, not a complete chimney kit. The fireplace installation requires the listed chimney, appropriate termination and all route-specific supports, firestops, flashing and other specified components. Quantity depends on the installation. The WRT4500 manual permits the listed 12DM or 12HT system and requires HT components for Canadian installations. Do not treat this part as a universal chimney for gas, pellet, oil or other appliances; verify the exact appliance listing before ordering.
For the WRT4500 family, maintain 2 inches of clearance from the outer chimney surface to combustible construction. Minimum chimney height is 16 feet for a straight system or one elbow set and 22 feet with two elbow sets; maximum height is 50 feet, measured from the fireplace base to the termination flue outlet. A vertical chimney supported only by the fireplace must not exceed 20 feet. Offsets, support intervals and the selected termination must comply with the installation drawings.
Have the complete system selected and installed according to the exact fireplace manual and applicable codes. Do not substitute unlisted parts or mix systems without explicit manufacturer approval. Superior WRT4536/WRT4542/WRT4550 installation and operation manual, Rev P October 2025 provides the height-gain chart and exact accessory list.
