JOINING DISSIMILAR PIPE ILLUSTRATED

[LazyPup]

[kactuskid]

Really nice drawings LazyPup. I have a guestion, is it ok to use a brass fitting to connect galvinized piping to copper instead of a dieletric union? I see this alot and figured it to be a good substitute to ensure against electrolisis.

[HayZee518]

Zinc-Copper, Zinc-Brass is electrolytically active. The dielectric union eliminates the "battery" across the joint.

[LazyPup]

The code prohibits directly coupling copper to iron, but in addition to dielectric nipples and dielectric unions, it does permit the use of a 6 inch hardened bronze nipple.

In some jurisdictions the inspectors will permit valve bodies to be used as the transition fitting if the valve has a hardened bronze body but technically they would not pass for two reasons. 1. They lack the code minimum 6" length, and 2. there is no way to insure that the valve will be replaced with a hardened bronze body valve during future maintenance.

[WD8CDH]

Hi LazyPub,

How about those "dielectric nipples" that are just a galvanized nipple with a plastic lining? I can't see how they would work.

Ron

[Sauna]

Very useful indeed. Thanks for the drawings.

[JimV]

It seems to be pretty standard to use bronze valves with threaded galvanized pipe. Why doesn't that cause problems, since they are dissimilar? Also, I have been told that having copper and galvanized in direct contact will not only cause the galvanized to corrode at the point of contact, but will also cause problems downstream. Any thoughts?

[HayZee518]

just for ha-ha's take a look at the periodic table of elements from chemistry class back from high school. one side is active gasses other side is active metals. here you'll find Cu=copper, Zn=zinc, Fe=iron, Pb=lead, Tin=Sn. Bronze and brass are alloys of two metals. Brass is copper and tin, bronze is copper and nickel. so, if you mix any of the active metals you can create corrosion between the joints unless you use an alloy.

[jackmcmanus21]

very useful drawings, thank you!

[jackiensteve]

Thanks for the info! I have a question that no one in any of the big boxes can answer. We jackhammered the basement floor to remove an old cast iron bowl drain and to install a shower. The existing pipe into the floor drain is 2.5 inch cast iron. We need 2" pipe for the shower. WE have searched high and low for a male threaded reducer and can't find anything 2.5". whatever we use must also be able to have concrete poured on top of it. Would the illustration on joining cast iron and pvc work in lieu of not being able to find ANY 2.5" threaded pipes?