For those of you looking for an alternative to the original,
sometimes finicky (my replacement used cap wouldn't thread on) Water
tank spout cap:

This is my fix for the water tank drain cap that you might have
missing/leaking:  I bought a $15 PVC tap from the Home Builder Supply
store along with a fitting that almost goes right over the downspout
of the tank. (The fitting screws onto the tap)  I had to lightly sand
the Polyethylene tank spout so that the fitting & tap would fit onto
it then epoxied it on.  It has worked slick ever since (been on there
since winter and have filled the tank several times with no sign of
leakage).

Some of you have seen this before but for those that haven't...

http://s1003.photobucket.com/albums/af155/onsight2003/?
action=view&current=DSCN6762.jpg

Trevor Reynolds
Airdrie, AB, Canada,
'91 GL 2Wheel drive, AT, Westy "SEN".
http://westfalia-91restore.blogspot.com/