Correct pipe fittings for steam lines

Peter Sagan

I am replacing an old steam boiler and need to redo some steam piping. What fittings should be used?
The old system has the thick gray cast-iron fittings.
Do I really need to use the same type fittings (they are really expensive), or the thinner black malleable fittings will do, too?

Alan(CaliforniaRadiant)Forbes

Do the right thing

Use the cast iron fittings. It will make it easier for the next guy.

Cast iron fittings are used because it's impossible to de-thread steam pipe once it's been used for a few years. Take a small hand sledge to a cast iron fitting and it shatters, making it easier to re-pipe. Try and do that with a malleable fitting and you end up just denting the fitting.

Alan

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Peter Sagan

Thanks for advice

Makes sense. I will use cast iron - at least in the most strategic places. Any other reasons not to use malleable fittings?

Peter

Alan(CaliforniaRadiant)Forbes

Previous thread

DATE: Feb 16, 2001
SUBJECT: Alan
NAME: Noel

They expand at different rates. The cast is less likely to leak on steam, and is
removable when it does leak. On hot water, maleable is fine, I think it's
because the hot pipe in a cold fitting is less drastic on water than on steam.
the pipe can get 150 degrees hotter than the fitting as steam approaches the
fitting. Somebody figgured it out ages ago that cast is the one to use on
steam....Noel

DATE: Feb 16, 2001
SUBJECT: use
NAME: Gary Fereday

cast where corroding wil be a problem the high carbon content of cast helps
stop corroding. but is brittle mal. ftgs corrode quicker but are soft ang bend
able Galvanizing does not work very well on steam. Wrot iron pipe has a
slag content in it that with cast iron helps stop corroding bgi ugh!



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Dingo

No offense ...

and kudos for asking ... but perhaps now you see why good contractors charge what they do ... and fittings are only aq drop in the bucket (cost wise).

But yes, do it right .. use the cast iron on steam.

FWIW

Dingo

Unknown

Either type of fitting is fine

A properly sealed fitting - cast or malleable - is fine for steam . I've been using malleable for over 18 years and hundreds of steam jobs . I have not seen a problem because of the material type used yet . We use Teflon and thread sealant , which makes spinning a fitting off years down the road alot easier .

It comes down to an aesthethic aspect . Cast looks more traditional on steam . But with the scarcity of cast fittings over 2 inch around here , it's malleable all the way . And there is nothing that looks worse than mixing and matching cast and malleable close together . Good luck on your project Peter .

Tony Conner

Malleable Iron...

...is just cast iron that has been heat treated in a furnace, to relieve it's brittleness. Malleable can stretch to a limited extent, without breaking, and as a result, has a slightly higher pressure rating (150 or 300) than the corresponding class of cast iron (125 or 250). You can break 125 cast iron by hitting it - malleable won't break. (Several shots with a heavy hammer will often let you unscrew a stubborn malleable fitting, though.) Other than the characteristics from heat treating, cast iron and malleable iron are identical.

Ken_8

C.I. fittings MORE expensive?

Not around here.

Once you get into the ~2" and over fittings, C.I. fittings are LESS expensive than black malleable! True, only by 10-15% cheaper (and under 2" they are 5-10% More expensive) - but I suggest you ask for actual prices once again.

This is not some "regional" issue. BM is BM, CI is CI Other than Ward, I don't even recall any other maker of any size in the biz (perhaps a few importers)

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Peter Sagan

Around here C.I. is MORE expensive

To give you an example, at my local plumbing supplies 3X21/2 tee, BM is $30 while CI runs for about $50.
One way or the other, they charge at least 100% than home depot, but HD does not carry sizes over 2".

Kal Row

do yourself a favor

put the major sections together using flange unions - at least to the boiler and to the house lines, so that if you run into a problem, and need to repipe - you will be happy you did - but do use anti-seize compound on the bolts, and if you can, get gortex gaskets - they seperate clean'n'easy - if your steam system is right - it's running between 2-4 inches of pressure - and leaks should not be a problem - if your pressures are getting beyond 1 pound, then leaks are the least of your problems -

Ken_8

Just called my wholesaler here in

northern NJ and the price is:

3 X 2.5" BM tee @ $46.14

3 X 2.5" CI tee @ 45.46

Both however, are made in the U.S.A! How about yours?

Go figure!

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Peter Sagan

I live in Jersey, too

Just for the record, at my local plumbing supplies (Central Jersey):
3 X 2.5" BM tee @ $29.89
3 X 2.5" CI tee @ $50.67

One way or the other to me it is still a racket.
In Home Depot 2" BM tee is just $4.98. It is a shame they do not carry larger sizes.

patrick linhardt

cast iron fitting prices

The Home Depot looks good here because it does not stock, and therefor does not quote prices above 2". The reality is the price jumps quite a bit from 2" to 2-1/2". At the supply house where I work a 2" C.I. tee is $7.65, a 2-1/2" C.I. tee is $19.89, all American for reference.
Its the economy of scales. The manufacturer produces way more 2" fittings than 2-1/2" because the market uses way more so they are cheaper to make. We only see a 1/2" difference in pipe size, the manufacturer sees a huge difference in usage.
Our cast iron vs. malleable pricing is very close, can go either way.

Ken_8

Is that quote for

American made fittings?

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Peter Sagan

Home Depot sells Chineese, of course.

I am not sure about plumbing supplies warehouses.

Ken_8

Are you saying...

Home depot actually stocked a 3x2.5" tee in both B.M. and C.I. - and both were chinese manufacture?

I truly am amazed!



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