Air Compressor Tank Won't Drain

[Jaja]

I have a new to me Craftsman oiless unit - Model #919.165570

It has a drain that looks like this:

When the tank moves you can hear the liquid inside so tried draining it, Nothing. So next I took out the drain plug and again Nothing came out. Next I put the drain plug back in and turn it on to fill the tank and then took out the drain plug expecting it to shoot like a rocket. Nothing....at 100 PSI only a few dribbles. So I guess this means it full of sludge somehow since it's oiless. Next, with the drain plug removed I stick a screwdriver in the hole expecting **** to start shooting out (it's still got 100 psi) and nothing...I can feel some resistance inside the drain hole. Does the pipe plug that the drain valve screws into have a screen over the hole?

I tried to remove the pipe plug like in the pic above to see but I only had a crescent wrench with me and the plug wouldn't budge. I'm thinking of either replacing the plug or drilling it out, chasing it with a tap and installing a new ball valve drain.

Any thoughts/insights are appreciated.

 

[cvairwerks]

Sounds like there is bunch of scale and **** built up and bridging over the drain area. Probably a good idea, if you can't get it to drain easily, is to borescope it and see what's going on.

 

[Yankeefarmer]

Don’t try to poke it with pressure in the tank. On my old compressor I did that and ended up with small rust particles embedded in my hand. Hurt like hell, too, when I got blasted when the “plug” let go. On my current compressor, which has a drain plug just like you show, I used a small diameter punch to clear the opening after removing the drain plug/valve. I felt resistance like you note, but I seem to recall just giving it a firm push and it penetrated. The plug was a thick goo of oil/water emulsion.

 

[Jaja]

I was a bit worried about the pressure so I did all this outside with the tank tipped on back (it's a vertical model) and "hid" behind the edge as I was waiting for that drain plug to shoot out. Very anticlimactic. I'll try the same as you suggested @Yankeefarmer and I've got some bore brushes on the way to clean out the drain hole.

 

[rlitman]

Don’t try to poke it with pressure in the tank. On my old compressor I did that and ended up with small rust particles embedded in my hand...

OUCH!

I'd suggest letting the air out, and then using a drill bit twisted between your fingers to pull out the crud.

In the future, if you can, use a ball valve for your drain (piped into a bucket through something to strain it and reduce the noise). The larger opening of a ball valve is less likely to clog. And if it does clog again (which may happen until you remove all the accumulated crud from your tank), you can clean it out like me (I had to do this twice):

Install a pipe ****** onto the ball valve. Then clamp a hose onto the pipe ******. Bend the hose a little where it exits the ******, and poke a long drill bit (like a 12" long 1/4" twist bit) through the hose. Now, you can open the valve and reach through it with the drill bit, staying clean-ish while what gets blown out follows the hose.