I have a 60 Gallon vertical ASME certified tank (W.P. 200 PSI at 450 Deg F) from 1986.
It looks good on the outside, just a bit of surface rust on the feet.

Tapping the tank all over, including the bottom sounds good, I don't expect any pinhole leaks.
I tried using a small (cheap) bore-scope camera to see inside, but that dud not work well, other than to know the inner walls are fairly dirty.

The little pit of water that came out when I removed the drain valve (maybe 1/4 cup or so) ran clear with a little oil but no rust color.

I know the "Right" thing to do is get it hydro tested and/or have the thickness measured, but in real terms, what is the chance it is not a good tank?

Seems almost every tank failure is either a horizontal tank or a story of a failed (or missing) pressure relief valve.

Bringing this discussion over here since we are off the pump and onto the tank:
forums.mastertoolrepair.com/index.php/fo...or-pump?start=6#1955

N_Jay wrote: I'll be looking it over more carefully this weekend when I test the tank. (All the YouTube videos have me nervous).

Going to do the grease gun test to about 265 PSI
1.5X of 175 PSI that I plan

I don't really want to stress it to the full 300 (1.5X the 200 W.P. on the tag.

MTR wrote: Here is my take on using older air tanks:

Old tanks normally will pin hole out eventually rather that catastrophic failures as long as they have a good working safety valve in place.
But there is always that one exception and who wants to take that kind of chance.

The serious accidents happen when safety valves have been plugged off and a pressure switch or starter contact points get stuck.

Tanks that have been in constant use are normally considered safe, because they rust slowly to a pin hole state. But tanks that have been left in storage can be a lot more risky as the rust can be over a large area weakening the bottom. Constant use tanks also have a film of oil and that helps reduce rust inside.

The other failure for tanks is vibration stress cracks. Usually at welded corners of the top plate and legs.
People will be tempted to weld on those cracks. That is a major hazard for sudden failure.
It is illegal to weld repair ASME tanks unless sent back to a ASME facility.

- MTR

Well as a hobbyist I don't keep my compressor on at all when I am not using it.

Once I test it out (Thoughts on going to 300 PSI?) my plan is to add a second safety valve and probably a new switch.
I know a lot of people that keep there compressors powered and charged at all times.
My habit is a hobbyist has always been to only power it when I need air. (Leaving it charged but usually well under the full pressure due to draining water and testing safety valves.

I have seem a lot of really ratty tanks that were in service, and I passed up due to looks.

Given how thin the tanks are on modern compressors, and the number of people who really do not know anything that buy them at home depot, if the risk was that high we would be hearing about a lot of blown out garages and basements.

That is not stopping me from spending a few dollars to give the tank a stress test. (Thinking I will leave it about a week.