Annoying Drip Around Freshwater Drain Tap

Hi All,
A slow drip has developed between the drain tap and the freshwater tank on my year 2000 Symbol. I noticed it when I was flushing the system for the start of the season. It had some sort of white sealant around the body of the tap and the tank which had disbonded. It looked like quite a neat job so I assume that it had been on there from new. I've removed the sealant and thumbed on some boss white in its place and time will tell if it has cured the leak or not (see photo).

My question is does anyone know if the hole in the tank is threaded or whether there is a locking nut on the inside of the tank that the tap screws onto like in a waterbut? I'll like to unscrew it to do a better job but don't want to make matters worse

Tried uploading photo but given up on that now

What photo??

Of course the tank is not threaded, you can't expect A/S to make things easy!
Years ago I had the same problem when the tap lever broke, I started unscrewing it & realised there was a locking nut on the inside, so I waited until everything had dried out to put a load of sealant around the tap.
I now have to use pliers to turn the tap. I did think of jacking the van up & trying to get my arm to the locking nut but took the easy way out.

I have just changed the drain tap on my fresh water tank on my 1998 Symphony. Very similar to your picture. The tap has a lock nut on the inside of the tank so I cut the tap off with a junior hacksaw and was able to push the inside nut into the corner of the tank with my finger. The hole is not threaded and the tap I got from AS slid into the hole so I fixed it in with some sealant called "Sticks like S**t" (real name). I have left it for a couple of weeks while I did another job to do with the water system and filled the tank the other day and it didn't leak. Hope that helps