Its either your condenser is clogged, in which case, pop it out, and use a PLASTIC ruler to clear it out.
Or your maintenance plug's fallen out. If it is, pull your dryer out, turn it off and look at the back of the dryer near the bottom, there will be a rubber plug that needs fitting properly. A sure sign of this will be if water starts dribbling out underneath the machine.
If the caps fitted properly, but its wet underneath then the pipe work's cracked or holed, if this is the case you'll need to call a repair man out.
Hope this helps.
Evil Twin, October 2008
