May 7, 2026
From the 2024 UPC Illustrated Training Manual, Chapter 6, WATER SUPPLY AND DISTRIBUTION
610.2 Pressure Loss. Where a water filter, water softener, backflow prevention device, tankless water heater, or similar device is installed in a water supply line, the pressure loss through such devices shall be included in the pressure loss calculations of the system, and the water supply pipe and meter shall be adequately sized to provide for such a pressure loss.
No water filter, water softener, backflow prevention device, or similar device regulated by this code shall be installed in a potable water supply piping where the installation of such device produces an excessive pressure drop in such water supply piping. In the absence of specific pressure drop information, the diameter of the inlet or outlet of such device or its connecting piping shall be not less than the diameter of such water distribution piping to the fixtures served by the device.
Such devices shall be of a type approved by the Authority Having Jurisdiction and shall be tested for flow rating and pressure loss by an approved laboratory or recognized testing agency to standards consistent with the intent of this chapter.’
Devices such as those noted above will cause pressure drops in the system and this resultant loss must be included in the pressure loss calculations when sizing the system. The size of the water supply piping and meter is then designed to offset the pressure drops caused by the frictional losses through these devices. The manufacturer of the device will provide the pressure loss factor in its installation material.
It is possible that after pressure loss calculations are completed and gallons-per-minute flow is taken into consideration, the installer could have a larger size of pipe than the inlet and outlet of the device. This is allowable and not considered a prohibited reduction of flow as long as the calculations are provided to the AHJ. When the pressure loss factors are unknown, the inlet and outlet of the device causing the pressure loss must have the same diameter as the supply piping.
From the 2024 UMC Illustrated Training Manual, Chapter 8, CHIMNEYS AND VENTS
802.5.11 Space Surrounding Lining or Vent. The remaining space surrounding a chimney liner, gas vent, special gas vent, or plastic piping installed within a masonry chimney shall not be used to vent another appliance.
Exception: The insertion of another liner or vent within the chimney as provided in this code and the liner or vent manufacturer’s instructions. [NFPA 54:12.6.8.1]
The installation of nonmetallic gas vents in an abandoned chimney or a chase with a gas vent in it is a practical solution to an existing unlined, oversized or failed chimney. When installing vents in a chimney space, all of the vent material manufacturer’s installation requirements must be followed. If required by the vent manufacturer, penetrating the masonry chimney to install supports might be necessary.
When using an abandoned chimney as a chase for multiple vents, care should be taken to ensure that the vent materials are compatible and that vent failure does not result inadvertently. Category I or III gas appliance vent gas temperatures can exceed 300°F (150°C). Contact between the high-temperature Category I or III vent material and the PVC vent pipe can cause the PVC pipe to degrade or soften to the extent of failure. With the chimney opening sealed around the vent pipes, the products of combustion, which can escape from the failed PVC pipe, will be trapped in the chimney. These gases could eventually leak back into the living space or corrode the other nearby vents.
(This is not to be considered the official position of IAPMO, nor is it an official interpretation of the Codes.)
IAPMO
IAPMO develops and publishes the Uniform Plumbing Code®,the most widely recognized code of practice used by the plumbing industry worldwide; Uniform Mechanical Code®; Uniform Swimming Pool, Spa and Hot Tub Code®; and Uniform Solar Energy, Hydronics and Geothermal Code™ — the only plumbing, mechanical, solar energy and swimming pool codes designated by ANSI as American National Standards — and the Water Efficiency Standard (WE-Stand)™. IAPMO works with government, contractors, labor force, and manufacturers to produce product standards, technical manuals, personnel certification/educational programs and additional resources in order to meet the ever-evolving demands of the industry in protecting public health and safety.
Last modified: May 9, 2026