Comparison of Gas Boiler Fittings

Commonalities

• Because operation, efficiency and safety are the common goals of all boiler manufacturers, all boilers must have a port through which cold water enters the machine, a port from which hot water or steam leaves, a port through which natural gas or propane enters and a flue for the combustion gases. Combustion air is not typically drawn through a fitting. The physical size and the working capacity of the machine determine which fittings are used. In residential applications a 1/2-inch copper tube is the norm for the gas line and both water pipes. In commercial applications where a number of sinks or bathrooms could place a simultaneous demand on the hot water supply, a 3/4-inch main outlet pipe is standard, which is reduced down to 1/2-inch to serve each outlet. In industrial applications, the use of 2-inch iron pipe is a practical minimum. The proper sizes for all pipework and fittings are determined by the maximum anticipated load that could be put on the boiler. Always check with your local code enforcement office to ensure your proposed installation satisfies its requirements.

Materials

• Brass fittings are most commonly used on compression and flare fittings, where deformation of an olive -- a ridged metal “washer” -- is the method for leak prevention. Copper fittings are typically more cost-effective but must be soldered in place to seal the system; this requires both specialized tools and considerably more time. Nonetheless, according to Copper Development Association, 94 percent of all professional plumbers use copper in their installations.

Safety Valves

• Safety valves are designed to prevent boilers from exploding. Properly called temperature and pressure -- or T&P -- valves, they provide an otherwise sealed and controlled method of venting extremes in temperature and pressure. Safety valves are sized according to the maximum capacity of the boiler and the volume of steam that volume could create; the inlet bore of the safety valve’s port is determined by the capacity of the boiler. There must be an unobstructed discharge pipe from the safety valve to a location where scalding water can do no harm; the bore of the discharge pipe must be equal to or greater than the bore of the inlet port.

Steam Boilers

• Because of the extremely high temperatures and pressures at which they function, steam boilers have a number of unique fittings. Steam boilers should be fitted with a stop valve, also called a crown valve, to cut the boiler off from its pipework system. The stop valve must be sized so that it can quickly isolate the boiler in the event of an emergency. Steam boilers should also have at least one pressure gauge installed; the physical size of the fitting port is typically around 1/2-inch, regardless of the size of the boiler.

Fittings for Obsolete Boilers

• There are specialized companies that manufacture boiler fittings that can no longer be found on the open market. They invest great care in ensuring their products match the originals exactly in both size and appearance.

A Word of Caution

• Although not strictly a fitting on the boiler, a pressure governor -- commonly called a regulator -- is an important fitting on the supply line to propane-fired gas boilers. No propane appliance should ever be used without a regulator.