Where to buy water tank fittings ?

Have you tried Lowes sharkbite?
Menards Has similar. these fittings work very well.

They are standard pipe thread

Half inch NPT is pretty common, basically ubiquitous. I would think the other big box hardware stores (HD or Lowes) should have an assortment of Apollo PEX fittings and/or brass. Any good local hardware store should have what you need too. HD usually delivers the next day, as many other online stores if you come up empty-handed. Good luck!

enblethen wrote:
Have you tried Lowes sharkbite?
Menards Has similar. these fittings work very well.

Don’t understand the shark bite pex recommendation? All he needs is a few fittings and a valve or 2.
It also virtually impossible that any of the big box stores or any hardware store for that fact don’t have a selection of 1/2 to 1-1/2” pipe fittings and valves in at least 3 different flavors (plastic, brass or galvanized).

What’s mil? Mil-spec? Just get some fittings that are npt