Dielectric unions

: I see dielectric unions separating steel pipe from copper tubing. I dont see any dielectric unions separating steel pipe from copper when there is a brass valve in between. One is a plumbing system system and the other is a heating system. Is there a reasonable explanation for this?Excuse me BUT I think what you may have seen copper/brass connected to Galvanized piping.You normally dont get a reaction of ferrous and non ferrous metals. When you get the electrolytic/Gavanic action is where zinc comes into play. For example sprinkler piping is normally made of black steel and the sprinkler heads are made of brass NO reaction. Hydronics black piping and Brass valves no reaction. Steam piping steel and Brass valves again no reaction. A gas cock is made of brass and the piping normally black steel. Now consider this Red brass is made of 85% copper and 15% Zinc and it can last over 100 years no problems.Yellow Brass is 60% copper and 40% zinc ( very popular during the WW 2 wars years to conserve copper) becomes very brittle due to Dezincification. If you mix copper or brass with a Galvanizeed pipe or fitting the Galvanized will corode.Galvanized is a zinc covering over black steel. Many times you can mix Galvanized piping with brass BUT it has to do with the medium being carried. A lot of time on air lines Galvanized piping is used in lieu of black because of large amounts of condensation from the compressiors. Even with brass globe and brass gate valves they dont show any signs of the corrosion associated with mixing of metals. This the the reason an Anode rod is also called a suicide rod as it takes the hit instead of the metal tank. Due to the minerials in the water which also can and do cause corrosion. I hope this helps answere your question. Respectifully… Sylvan.

Brass is between copper and steel on the nobility scale, so it separates the two and acts as a buffer to reduce electrolysis. A dielectric union is more cosmetic than functional. The water is the medium that enables electrolysis to function, and so it bridges the dielectric union. Just as a water heater without an anode rode will rust out quicker than one with a functioning anode. But a heater with no water in it will last forever. In this situation, it is the water that allows the anode to coat and protect exposed surfaces on the interior of the tank.: I see dielectric unions separating steel pipe from copper tubing. I dont see any dielectric unions separating steel pipe from copper when there is a brass valve in between. One is a plumbing system system and the other is a heating system. Is there a reasonable explanation for this?

: Brass is between copper and steel on the nobility scale, so it separates the two and acts as a buffer to reduce electrolysis. A dielectric union is more cosmetic than functional. The water is the medium that enables electrolysis to function, and so it bridges the dielectric union. Just as a water heater without an anode rode will rust out quicker than one with a functioning anode. But a heater with no water in it will last forever. In this situation, it is the water that allows the anode to coat and protect exposed surfaces on the interior of the tank.: : I see dielectric unions separating steel pipe from copper tubing. I dont see any dielectric unions separating steel pipe from copper when there is a brass valve in between. One is a plumbing system system and the other is a heating system. Is there a reasonable explanation for this?The reason you normally dont see it on heating systems Or for that matter Sprinkler systems is NO OXYGEN in either. To be more exact on a hydronics system ( hot water heating) Like sprinklers the system is closed and very little make up water is required. As we all know fresh water contains oxygen. Oxygen causes rust corrosion etc. I have taken apart old how water piping that is over 60 years old and still looking like new. Normally you do not need any dielectric fittings ( not just unions)if your using Bronze ,coppper, Brass and conneecting to steel piping or fittings. When you connect copper,bronze, brass to piping with a zinc coating ( Galvanized) POW chemical reaction and good by system. Sylvan