Vintage Sanborm air compressor has NO drain valve!

by Chris C.
(Montreal Canada)


I just acquired a vintage Sanborn 10 gallon air compressor with a small piston pump and 3/4HP 120V electric motor.

After adjusting the loose pulleys that made it so loud when I got it (no doubt the reason I got it for $20!), I noticed there is no drain valve whatsoever on that tank!

Since it can't possibly be, otherwise the tank would be full of water by now, I was wondering whether this tank didn't have some sort of an automatic drain whereby the air is taken from the bottom of the tank so it can never accumulate there (it would be essentially siphoned out through the air hose)

Am I missing something there or do I make sense?

I looked carefully on the tank and besides the outlet from the compressor pump there are no bungs whatsoever to indicated that perhaps a former owner closed one up, no repair welds either. It used to be red, now it's green.

Model is 44A75-10

Any advice would be greatly appreciated!

Chris C. in Montreal

Comments for Vintage Sanborm air compressor has NO drain valve!

Click here to add your own comments

Aug 09, 2015
Sanborn drain
by: Bill

Actually Chris, I'm nowhere near Pointe Claire. That's the H.O. of the software company I use.

I found a parts list for your compressor on line, and it definitely had a drain valve in the tank, so I don't know where the combination PRV and drain valve comes from.

And, I've never seen a PRV that's also a tank drain valve. One is a safety device - the PRV - and I can't see it's operation being contaminated by the water and sludge that comes out of a compressor tank.

If you wish to upload an image, start a new thread in the Sanborn forum, cross reference to "Vintage Sanborm air compressor has NO drain valve!" and I'll move the image to this thread.



Aug 09, 2015
Found it but never seen one like it before!
by: Chris C.

Thanks for your previous answer, Bill! Nice to see you're from my parts of the world, maybe I should drop by next time I'm Pointe Claire :-)

Well, I had a close examination and there are NO external drains whatsoever - BUT I discovered that the safety valve also acts as the drain! Which brings up my next question: HOW does it possibly work? Is it some kind of internal siphoning system?

I'd join a picture but there is no option to add one here.

Aug 08, 2015
Sanborn compressor tank drain
by: Bill

Hey Chris.

The original Sanborn 44A75-10 had a tank drain cock, bottom of the tank near the end under the motor side of the compressor, between the leg and the end of the tank. No automatic drain that I know of.

If your tank has no drain now, someone has changed tanks I would guess.

You do need to have the drain as you so correctly point out.

If the tank no longer has one, get it drilled and tapped for a drain cock.


Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Sanborn Compressor Issues.