Haw. Code R. § 12-223.1-11 - Acceptable installation of temperature and pressure relief valves for potable water heaters

The following shall apply to the installation of temperature and pressure relief valves for potable water heaters:

(1) Temperature and pressure relief valves shall be installed by either the water heater manufacturer or installer before a water heater is placed in operation;

(2) Temperature and pressure relief valves shall be connected directly to a tapped or flanged opening in the top of the water heater, or to a fitting connected to the water heater by a short nipple;

(3) Temperature and pressure relief valves shall be installed with their spindles upright and vertical with no horizontal connecting pipe, except when the temperature and pressure relief valve is connected directly on the water heater vessel with no more than four (4) inches maximum interconnecting piping, the valve may be installed in the horizontal position with the outlet pointed down. The center line of the temperature and pressure relief valve connection shall be no lower than four (4) inches from the top of the shell;

(4) No piping or fitting used to install the temperature and pressure relief valve shall be of nominal pipe size less than that of the valve inlet;

(5) When a potable water heater is fitted with two or more temperature and pressure relief valves on one connection, this connection shall have a cross-sectional area not less than the combined areas of inlet connections of all the temperature and pressure release valves with which it connects;

(6) When a Y-base is used, the inlet area shall be not less than the combined outlet areas;

(7) When the size of the water heater requires a temperature and pressure relief valve larger than NPS 4 two or more valves having the required combined capacity shall be used;

(8) When two or more valves are used on a water heater, they may be single, directly attached, or installed on a Y-base;

(9) A threaded connection may be used for attaching a temperature and pressure relief valve;

(10) Temperature and pressure relief valves shall not be connected to an internal pipe in the water heater or a cold-water feed line connected to the water heater;

(11) No shutoff valve of any description shall be placed between the temperature and pressure relief valve and the water heater or on discharge pipes between such valves and the atmosphere; and

(12) The discharge from temperature and pressure relief valves shall be so arranged that there will be no danger of scalding attendants. When the temperature and pressure relief valve discharge is piped away from the water heater to the point of discharge, there shall be provisions for properly draining the piping and valve body. The size and arrangement of discharge piping shall be such that any pressure that may exist or develop will not reduce the relieving capacity of the relieving devices below that required to protect the water heater. The following shall apply to discharge pipes:

(A) When a discharge pipe is used, it shall be not less than the nominal size of the valve outlet, and shall be as short and straight as possible, properly supported and so arranged as to avoid undue stress on the valve. When an elbow is placed on a temperature and pressure relief discharge pipe, it shall be located close to the valve outlet;

(B) Where multiple valves relieve into a common discharge pipe, the cross-sectional flow area of the common discharge pipe shall be equal to or greater than the sum of the individual temperature and pressure relief valve discharge pipe areas;

(C) Discharge piping shall be rated for the discharge fluid conditions of pressure and temperature including a minimum and maximum design temperature. Material selection for the discharge piping shall consider the reduction in material toughness at the low end of design temperature and the reduction in material strength at the high end of design temperature. Rigid pipe or tubing should be used for discharge lines that carry hot water or steam;

(D) Plastic discharge pipe and fittings are permitted (when compatible with the process fluid, system design temperatures, and other ambient conditions such as light and humidity) and shall conform to NSF/ANSI 14 Plastics Piping System Components and Related Materials; and

(E) Discharge piping shall be rated for any static pressure present and the back pressure that may develop when the pressure relief device is at full capacity. Where multiple pressure relief devices or vents discharge into common piping, the back pressure that could develop due to simultaneous flow from all sources shall be considered.

Notes

Haw. Code R. § 12-223.1-11

[Eff and comp 12/21/2019] (Auth: HRS § 397-4) (Imp: HRS § 397-4) Am and comp 9/8/2024