Dielectric Union or Not?

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    • #275346
      Aquarian

      I have an oil fired residential boiler. I have noticed that there are no dielectric unions installed between the 3/4″ copper pipe heating pipes and the black steel NPT threaded pipes in the boiler’s supply or return side piping. There is no dielectric union used also for the cold water supply to the boiler. Should there be dielectric unions in any of these locations?

      Joe

    • #291751
      TheLocalPlumber
      Participant

      Joe, Dielectric unions are a thing of the past. In fact they may cause more harm then help. The new code editions do not include dielectric unions, they recommend a seperation be used with a piece of brass piping not to be less then 6″.
      Good Luck to you,
      Bill
      The Local Plumber
      Tustin, California http://www.TheLocalPlumber.com

    • #291752
      joecarjoe
      Participant

      Thanks for the info Mr. Local Plumber.

    • #291753
      SylvanLMP
      Participant

      You do not need isolation fittings like a dielectric unions or nipples when mixing ferrous and non ferrous metals like copper to black pipe ESPECIALLY in a closed system where little or no oxygen is present.

      Think about the following

      Steam System Black steel with cast Iron radiators and BRASS valves.

      Fire suppression piping BLACK STEEL Brass OS&Y valves and BRASS sprinkler heads.

      Gas piping Black steel Brass gas valves.

      Water Mains Cast Iron class 22 with copper Type K gooseneck connections

      Fire hydrants cast Iron Brass nipples for the fire hose connection.

      Depending on the type of service and piping materials like copper/brass, etc., connected to a galvanized line here could be a major problem.

      Closed hot water or chilled water system not a problem as long as your not mixing zinc.

      This was a major problem in by gone days when folks trying to conserve copper made an alloy called yellow brass in stead of red brass.

      The red Brass 85% copper 15% Zinc gave years and years of trouble free service BUT the yellow brass 60% copper 40% Zinc had all kinds of problems like becoming brittle like due to dezinification

      Using a dielectric fitting is not a bad idea but in this case it really is not warranted UNLESS you have a major make up problem where fresh water (lots of oxygen) is in this system as Oxygen in water is what destroys ferrous metals under most conditions.

      Even the older cast Iron water mains are protected by use of hot applied Coal tar enamel.

      The better codes (not the codes where officals who are being paid off by some home builders) do want some type of protection where a conditions may exist where a premature piping failure may occur do to mixing various materials.

    • #291754
      SylvanLMP
      Participant

      You do not need isolation fittings like a dielectric unions or nipples when mixing ferrous and non ferrous metals like copper to black pipe ESPECIALLY in a closed system where little or no oxygen is present.

      Think about the following

      Steam System Black steel with cast Iron radiators and BRASS valves.

      Fire suppression piping BLACK STEEL Brass OS&Y valves and BRASS sprinkler heads.

      Gas piping Black steel Brass gas valves.

      Water Mains Cast Iron class 22 with copper Type K gooseneck connections

      Fire hydrants cast Iron Brass nipples for the fire hose connection.

      Depending on the type of service and piping materials like copper/brass, etc., connected to a galvanized line here could be a major problem.

      Closed hot water or chilled water system not a problem as long as your not mixing zinc.

      This was a major problem in by gone days when folks trying to conserve copper made an alloy called yellow brass in stead of red brass.

      The red Brass 85% copper 15% Zinc gave years and years of trouble free service BUT the yellow brass 60% copper 40% Zinc had all kinds of problems like becoming brittle like due to dezinification

      Using a dielectric fitting is not a bad idea but in this case it really is not warranted UNLESS you have a major make up problem where fresh water (lots of oxygen) is in this system as Oxygen in water is what destroys ferrous metals under most conditions.

      Even the older cast Iron water mains are protected by use of hot applied Coal tar enamel.

      The better codes (not the codes where officals who are being paid off by some home builders) do want some type of protection where a conditions may exist where a premature piping failure may occur do to mixing various materials.



      SylvanLMP

    • #291755
      Guest
      Participant

      Dear Mr Sylvan,

      Thank you so much for your wonderful comments. I really enjoy reading your postings and you are a very remarkably intelligent man. I enjoy both your wit and your knowledge and look forward to reading your postings in the future……
      Thanks Again,
      Susan
      South Florida

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