Best Of
Re: Excessive Water Hammer / Knocking trying to find source
Flush it. Give it a good thorough skim.

Re: Excessive Water Hammer / Knocking trying to find source
Yep. Flip the tee so the valve handle points out. Then if you unscrew the valve, you have a straight shot into the boiler.
Re: Burner technicians -what’s going on in this industry?
Trade unions have always been a liberal cornerstone. Has that changed?
Re: Estimated life expectancy?
Megasteam without a doubt……
Time to start sizing up everything.

Re: Gas hissing from water heater combustion air inlet area
Not necessarily a bad thing. It could just be the way the pilot light sounds. However, there could be a leak somewhere on the gas valve and or tubing feeding the burner/pilot light.
Spray this on the valve and tubing etc. to check for leaks.

Re: Excessive Water Hammer / Knocking trying to find source
Things to talk to the installer about:
need a new vent here
need a vent installed here, probably Gorton 1's in both places'
as @tcassano87 says, this copper connection should drop straight down to the wet return
your water quality is bad. Boiler needs to be flushed and skimmed some more.
id also flip this reducing tee so the drain cock aims into the boiler- makes flushing the mud leg easier.
lastly, they should check pitch on your lines to make sure there're no sags or pockets.
Re: Pipe Dope for 2" Home Oil Tank Lines?
Your right but the Pump Mfgs (at least Suntec) pushed it through.
Re: Weird exhaust smell Nat. Gas GV3 not making C.O.
With most gas fired boilers, you will get a smell in the exhaust, of various nitrogen oxides. Quite distinctive, once one learns what it is. That said, you should NOT be smelling it anywhere except rather near, and downwind of, the exhaust port on the building. Anywhere else and you have an exhaust leak.
Problem. Nitrogen oxides aren't good for you. Nor, for that matter, is low level CO which, unless you have a low level detector (down to a few ppm — most commercial ones are limited to 100 or so, which is get out of Dodge level) you won't detect. That's not good for you either.
Something is amiss in the exhaust train, and it would be well to find it.
Re: Apartment Tankless Hot Water
Hi, Is there anywhere else you could move the water heater, where space is less of a concern? Also, is there a place where a heat pump type heater could go? You won't save much space with tankless, and the maintenance is a thing. It's not set and forget like tanks can be. Not trying to rain on the parade, just personal experience raising its head 🐲
Yours, Larry