O/T Plumbing Question?

Were Adding a heater in the garage, hooked into the lines from the outside wood boiler, can you use galvanized or black fittings from copper coil to Pex Tubing or should you use brass & copper fittings?

copper will corrode when attached to iron pipe. best to use brass or PVC

I fear PVC would melt in that application. It did when I tried to patch up my water heater.

Definitely don't use black iron pipe for water, it is for gas only. As was said, iron (galv or black will corrode with copper. Home cheapo and Lowest and Ace hardware has the adaptors you want to go right onto pex.

When attaching dissimilar metals you need to use DIELECTRIC ISOLATORS

1. Provide non-conducting dielectric connections wherever jointing dissimilar metals install approved factory fabricated isolator on piping systems. Epco Type GX or FX, Maloney Type E, or Capital Type CS or F.

2. Dielectric pipe fittings shall meet all requirements for tensile strength of the pipe fittings as listed in the Federal Specifications, Specification and Codes for the Plumbing Industry and ASME Engineering Specifications.

3. Unions shall be rated at not less than 250 psi. Fittings shall meet the Standards of ASA No. B16.8 ASME.

4. All plating shall comply with the Federal Specification.

5. The design of the union shall eliminate any flow restriction. The gasket shall be specifically designed for the project application.

6. The installation of the union shall allow for expansion and contraction.

7. Provide a Certificate that certifies that the dielectric union has been tested by an independent testing laboratory and meets WW-U-516B, ANSI-B-16.39, ANSI B2-1, and Class 1 ANSI-B1-20-1.
8. Submit unions for approval.

9. Provided isolating fitting in gas piping at each building entry, except where exterior gas main or branch is plastic.

ERP is right, you have to use a dielectric fitting if you have different metals.

However, if you are going directly from copper piping to PEX tubing, you can use a standard fitting for that purpose. There are push on style, crimp style, and compression style, and the choice is up to you for which you would like to use.