March 12, 2026
From the 2024 UPC Illustrated Training Manual, Chapter 6 – WATER SUPPLY AND DISTRIBUTION
608.1 Inadequate Water Pressure. Where the water pressure in the main or other source of supply will not provide a residual water pressure of not less than 15 pounds force per square inch (psi) (103 kPa), after allowing for friction and other pressure losses, a tank and a pump or other means that will provide said 15 psi (103 kPa) pressure shall be installed. Where fixtures, fixture fittings, or both are installed that, require a residual pressure exceeding 15 psi (103 kPa), that minimum residual pressure shall be provided.
The residual water pressure required for any water supply system is 15 psi. Residual Pressure is the pressure available at the fixture or water outlet after allowance is made for pressure drop due to friction loss, head, meters, and other losses in the system during maximum demand periods (See Section 218.0). There may be certain fixtures or appliances in an installation that may require a higher minimum pressure above 15 psi. In this case, that minimum pressure will be the required minimum pressure. If the main line pressure cannot provide this minimum, the system must be designed using pumps, tanks or both to achieve the minimum required.
From the 2024 UMC Illustrated Training Manual, Chapter 13 – FUEL GAS PIPING
1308.11 Low-Pressure Protection. A protective device shall be installed between the meter and the appliance or equipment if the operation of the appliance or equipment is such that it could produce a vacuum or a dangerous reduction in gas pressure at the meter. Such protective devices include, but are not limited to, mechanical, diaphragm-operated, or electrically operated low-pressure shutoff valves. [NFPA 54:5.10]
If a low-pressure shutoff valve is installed, a manual-reset device is recommended. This device ensures that the gas will not come back on unexpectedly. It is very important to protect the gas supply system from low pressure and vacuum. If the equipment could cause low pressure or vacuum in the supply system, it could adversely affect the supply pressure of other customers on the line. The low-pressure situation may create a dangerous condition for an unsuspecting user, and it would be difficult to determine the source if caused by another customer.
(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: March 11, 2026