Threaded Pipe Connection Between Different Metals

[KenRad]

I have an aluminum filter housing that needs to connect to a pumped drain system made of copper. When the system is in use, it will operate at about 140F. Thread size is 2" NPT.

What connection should I make between the two materials? I'm concerned about threaded joint leakage due to differing expansion coefficients, as well as possible galvanic action.

I posted this on the Piping and Fluid forum, but it was ignored.

---KenRad

 

[cme]

That's a good question for the mfr. I would guess a brass stub then a union. That way they could change the stub quickly and with minimal cost.

 

[MintJulep]

What is the fluid?

 

[KenRad]

The fluid is water, with a slight amount of a detergent.

---KenRad

 

[DRWeig]

Say KenRad,

Unless I'm missing something, you should be able to get a standard dielectric union from a plumbing supply place to handle those two specific metals.

Good luck with it, let us know what you find out!

Old Dave

 

[ChasBean1]

I don't think there's galvanic concern between copper and aluminum (possibly similar oxidation potentials) - but don't quote me on this. Air coils are aluminum fins on copper... If you have any doubt, just put dielectric connector (close nipple w/plastic lining). Easy and cheap.

Good luck, CB