[Blackman]

This is a common problem and it has been covered in detail here before.
(Check the archives) It requires removing the access panel nearest the
drain valve, cleaning off the old sealant around the mounting plate inside
the tank, drilling out the two rivets that secure it to the skin, inspecting
and cleaning the mounting plate (and be very careful not to damage it as
they are not available , new, currently) and inspecting and cleaning the
area around where it mounts. (It is quite common to find the skin has been
damaged from previous installation riveting so the valve housing and O-ring
will not sit flat and therefore will leak. If this condition is found there
is a whole procedure for repairing it as best one can.) There is a
procedure for reinstalling it that would take a while to explain therefore
check the archives. It has to be installed and riveted “wet” with
appropriate sealant and then brushed over the rivet buck-tails and around
the base. The two outlet arches in the mounting plate must be clear of
sealant (again, see the archives) or fuel or water can’t get to the valve.

The short of it is not to attempt this without full knowledge of what you
are doing and you should never allow a non-experienced person to try it as
it can result in some really expensive damage

Ken Blackman
Air Mods N.W.

You will drain the tank, remove the drain valve. Now open the tank access cover. You need to get some brushable A2 or A1/2 sealant. You will not need much, you are just going to paint the back side of the 2 rivets that hold the blind fastener that the drain valve screws into. Not hard, but bright light, a good mirror, and a good cleaning will be your friend.

Then you will need the PRC1428 to reseal the access cover with the low adhesion stuff. 50 grams will do a cheetah cover.

Basically what Ken said.

Roscoe
Yankee Aviation