Is it necessary or desirable to use a dielectric union or coupling when connecting new gas lines to a gas meter? I have seen this done in some installations but not others.
It depends upon whether your gas utility uses metal supply lines with "active cathodic protection" or not.
If they do, then they apply a low voltage to their pipes to prevent electrolytic corrosion and the dielectric unions are needed to avoid shorting that voltage to ground through the home's plumbing and/or electrical grounding system.
Best to check with your gas utility and do what they say. AFAIK nonmetalic supply lines are the defacto stardard for new installations nowadays.
Thanks Jeff (and 73's) - I was unaware that the utilities used an active method to fight electrolytic erosion / transfer. This is a retrofit to an existing meter and a 50+ year old underground supply line, so I think it best I put the dielectric union in "just in case".
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