Importance of steam valve size

Tom Hopkins

Great to know! Thanks to both for the expert advice, belatedly.
Patrick North

Tom Hopkins

steam valve sizing

In sprucing up the rads in our 1-pipe steam system, I've noticed that most are equipped with 1-1/4" valves with a bushing to connect to the 1-1/2" port on the radiator. Because the larger valves are harder to find and much more expensive, I can see how this might have happened over time. Think this restriction is reducing system efficiency or causing problems in any way?
Just curioous,
Patrick North

Brad White_185

Not sure

that I follow...

Normally the hand-valve size is the same as the pipe feeding it.

The size of the main radiator tapping is not a consideration. The reason you might have a 1.5" tapping on a radiator is that the end section is but one casting which can be used on radiators from two to 40 sections. That one casting and master can serve so many combinations. Besides, bushings are relatively cheap.

If the valve is the same size as the pipe serving it and if the valve is fully open, the pressure drop is worth about 20 equivalent linear feet of piping. If sized for 2 ounces per 100 feet, that is about 0.40 ounces of pressure drop. Not worth considering.

Remember, if not for pressure drop, nothing would move!

Steamhead (in transit)

I agree

it's not a problem, Pat.

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