About a year ago I began to hear a hissing noise coming from the bottom of my air tank. I thought it was the drain cock leaking and didn't pay much attention. But no matter how much I tightened it, the noise persisted. About 6 months ago it got noticeably worse, so I quit using the compressor pending finding time to fix it. I could see no visible problem, but the noise was coming from SOMEWHERE.
So I finally took it down a couple of months ago. There is a crack in the bottom of the tank! Due to a poor design, there is no way to drain all the water out of it. The welded-in flange that the inspection plug screws into protrudes into the tank by about 1/4 of an inch. The drain cock screws into the inspection plug, so there is 1/4 inch of water in the bottom of the tank at all times. My tank had rusted through and could have unzipped at any time. If you have one of these tanks (or any tank with a 2 inch inspection plug in the
bottom) you might give it a look.
My 60 gallon compressor tank. It's only about 10 years old.
It has a 2" inspection plug in the
bottom - not a good design.
I poked boroscope in the tank and it showed how the weld flange protrudes into the tank, leaving a lip that water can't get over when you drain the tank.
The inside was rusted significantly.
You couldn't see anything wrong when there was paint on the tank, but I had to heat it to get the inspection plug out and that burnt off the paint. With the paint gone, the crack was obvious. This thing could have come unzipped at any time.
The new tank. The drain cock flange is only 1/2 pipe. The inspection plug is on the side where it ought to be. It probably weights 40 pounds more than the old tank. It's a much more substantial piece.