Help identifying this piping and fittings/couplers

[IPDQKWID]

Installing a water softener, including re-piping from the meter onward. I am trying to figure out what type of connectors are here before trying to uncouple everything. To the left of the gray-ish oxidized base under the black plastic part of the meter, there is a brass or cast copper nut which I think is threaded onto the gray-ish base. Out the other side of the nut is a brass nipple-like pipe. I cannot tell if there are threads on the end of the nipple-thing that enters the nut.
Is that some form of union? Do couplers come as just a nut? There's that tiny little hole in one of the hex-sides of the nut.
I'm wondering how much I can safely remove. That brass-ish pipe nipple has a ton of pipe wrench-like groove impressions in the part, and it is slightly out of round. I'm worried that might be a sign someone else tried to remove it, and couldn't.
Thank you for any insight.

 

[Bannerman]

cannot tell if there are threads on the end of the nipple-thing that enters the nut.

The brass nut, is likely securing a union fitting which is formed directly onto the meter end of the 3/4" brass nipple. Meter connections often do not utilize standard fitting sizes, so you will likely experience difficulty obtaining a replacement union to fit that 5/8" meter.

There's that tiny little hole in one of the hex-sides of the nut.

That hole is typically utilized for a security wire to pass through the nut, extending through a similar hole in another component, possibly located below the black plastic cover directly above the nut. When a meter is utilized to measure water consumption for billing purposes, the wire will be equipped with a numbered plastic seal, usually installed by the municipal water supplier when the meter was first installed. The seal will be similar to the one typically installed on an electric meter retaining ring.

A damaged/missing seal will indicate to the water/electricity supplier who is usually the meter's owner, that there was an unauthorized attempt to disconnect/bypass the meter. When a meter is serviced or replaced by an authorized technician, a new seal will usually be reinstalled, with the seal number recorded within the account file pertaining to that specific municipal address.

 

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[jasper07]

Sounds like you’re looking at a meter union connection. That big nut is likely part of the union, and the tiny hole might be for a seal or tamper tag. If the pipe looks damaged or stuck, someone probably did try removing it, go slow and maybe use some penetrating oil first.

 

[IPDQKWID]

Thank you both. The 5/8 thing caught my attention, Bannerman - I had to read up on meters, and that led me to meter couplers as a thing, so now I know what I'm looking at. I want to upsize the pipe to the 1" that the softener is made for, but now I can't seem to find a meter coupler that is 3/4 on the meter end and the other end a 1" NPT.

Do meter bodies require a special connector? Can I not just use an NPT coupler? I've seen the designation NPSM - Is that required for the meter flow rate to be measured correctly?

 

[piwopok1]

That tiny hole in the hex nut is the definitive clue that you are looking at a water meter coupling nut; the hole is designed for a utility’s wire tamper seal, and the assembly functions exactly like a union where the nut slips over the brass tailpiece and clamps its flanged end against the meter body using a gasket. Since you mentioned the brass nipple is out of round and covered in wrench marks, you should assume it is compromised and plan to remove the entire assembly containing both the nut and nipple rather than trying to unthread the nipple or reuse it, as new fittings will likely fail to seal on the deformed brass. Because the previous damage suggests the threads might be seized, apply a penetrating oil and strictly use the two wrench method (using a backer wrench to hold the meter body stationary while turning the nut) to avoid cracking the meter housing, then replace the setup with a fresh Water Meter Coupling Tailpiece Kit.
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