Malleable Iron or Cast Iron Fittings for 15 PSI Steam Systems?

Ken Sappio

I'm installing a new low pressure (15 PSI) steam boiler. Should I use cast iron or malleable fittings?

Keith_19

Use cast fittings. Remember that the maximum allowable working pressure of the boiler is 15PSI - that is the most pressure that the boiler can withstand without failing. The actual running pressure of the boiler will rarely raise to 2PSI - anything more than that, and you've made a mistake somewhere.

Unknown

Why

use cast instead of malleable ?

Keith_19

Because that's just the way it's done. Malleable are gas fittings. Cast are steam fittings. That's the way it is in NYC.

kevin_60

cast

I agree with Keith use cast.

bob young

malleable acceptable

YOU are correct Kieth but malleable is ok because i checked with the chief nyc boiler inspector & he gave it the green lite. keep in mind cast is more expensive if it is a marginal job .

Unknown

Hmmm ........

I keep hearing " cause that's the way it's done " .

But I'd like to know the reasoning behind why it's done that way .

BTW , I've used malleable on steam exclusively for almost 23 years . On well over 1000 installs ( residential ) , mostly in NYC . Never , ever had a problem using malleable .

Rich Kontny_3

Cast Iron

Allows you to break apart the fitting after the threads seize

gerry gill

lets not forget that they are both IRON.

the cast would allow you to break the fitting off if need be..still easier said than done..least for my 5'3'' body..both will obviously perform just as well in service..i usually use cast if i can just because most of the others don't..its my connection to the old timers i guess..but i'll also use mallable when cast is out of stock..which is frequently..i think its like RonJr. is suggesting that its more tradition than any realistic reason..my 2 pennies

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Charlie from wmass

I find that the threads in the cast fittings are more uniform. I also Feel with out sciece to back this one I know that the malleble fittings spread over time and leak, especially when someone torques the heck out of them. The cast fittings are more likely made in the USA and the malleble are often imported. I try to only buy USA made fittings in malleble or cast iron if I can. I had a gas job , small house, ran gas lines from meter to opposite end and did the pressure test. Sure enough 3 90's right at the start had sand holes. they were import fittings and I was not aware they were as wholesaler had always told me before if they were import or domestic. could not see holes but at a whopping 2.5 psi it leaked. Was on a job yesterday wearing my plumber hat and asked what I thought of the boiler the owners cousin had installed. It was a beautiful blue boiler stacked on the indirect and it had over 10 leaks that had frozen shut in the past 5 years on the Maleble fittings. Nice work but bad fittings. I often think when folks say I never saw a problem it is because they have not been told of the leaks or people think a few leaks are normal and fail to complain about them.

oil-2-4-6-gas

malleable is good for steam--its just as easy to cut and chop out nipples as it is to break cast (if enough room), malleable is a little bit cheaper ,,malleable is accepted by inspectors --(unless the inspectors are -programmed--"because cast is for steam") - you can use either 1 -for steam -

Jack Smith

I always thought

I always thought the reason for cast fittings was the difference in expansion rate between malleable pipe and cast fittings, allowing as the system is running for the pipe tp expand and tighten into the fitting. No leak. (I also like the fact that the fittings break apart during a replacement!)

bob young

COST EFFICENT

ONE point is that in the past cast iron steam fittings were half the price of malleable. now it is reversed. a plumber would never waste money un-necessarily. NEVER

Steamhead (in transit)

Cast Iron

is not all it's cracked up to be...

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Mark Eatherton

Gerry...

Tell me your method of cracking cast fittings. With help, I can generally break them free in about three swings.

ME

Jim Bennett

Bingo...

This is the way I learned it. Back in the day, cast fittings where less expensive, but perfectly acceptable for use on steam.

Now it has just become the way things are done. I personally prefer the look of a cast iron piped system, and try to use them when possible. I find that cast fittings are getting harder to come by now in my area. Especially eccentric reducers and reducing ells.

As far as taking fittings apart, I cut almost all the way through the band on the fitting with abrasive cut off wheel and then drive a small chisel end wise into the cut. Works great on cast and malleable and puts much less stress on the system beating on fittinfs with a hammer.

Jim