Draining air

[Skipoffools]

So I found an air tank, I assume it is the wet tank, behind the battery compartment. I opened the valve and pulled the cord and air and lots of water came out. But only one of my two air pressure gauges showed empty. The other is still sitting at 90 psi.

I looked all over and I cannot find another tank. I have heard talk of tanks that have a divider which makes it 2 in 1 tank. I don't see another drain though.

Help!

[cadillackid]

on my carpenter there was one air tank behind the batter compartment.. right near the Bendix AD-4 air dryer.. then farther back a few rows is my 3 in one tank that has 3 drains in it....

-Christopher