I know this is a piping code, but I posted this question here because it applies to Boiler External Piping.

In the above mentioned paragraph, it states:  "The stop valve or cock shall comply with the requirements of (C.5) below."

para (C.5) states: ..."valves or cocks shall be bronze, cast iron, ductile iron or steel."

Question:  since only the stop valve is mentioned, does that mean I can use a stainless check valve per para 107.1 as long as the material is listed in table 126.1?

Not so fast. The Code does not provide card blanch for materials to be used in any environment or service just because materials are listed in Table 126.1. The reference to C.5 applies to low temperature/pressure boilers and if a stop valve is installed of the permitted materials, the check valve should be close to the same material. Why would you want to install a stainless steel check valve? Galvanic corrosion could be a problem.

Have you heard of stress corrosion cracking in austenitic grades of stainless steel at around 160 deg F and higher in oxygenated, treated water?

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