leaking from outlet drain

ive got a 2005 neuvo es the drain outlet is leaking on the fresh water tank,looks like a previous owner has tried to fix it with a rubber compound .i have draine it completely and open up the inspection cap but i cant seem to get the nut off the outlet any help please

I guess you mean the nut on the inside, which is turning as you try to unscrew the drain tap? You just have to get inventive, as was shown in another recent thread with an adjustable spanner, gaffer taped onto a pole. You probably just need to break the grip of the sealant and then it should come off no problem.

thanks ill give it another go