Grey waste tank repair

[GeoffC]

I noticed water dripping from the corner of the grey waste tank on my Bavaria i740. The tank is mounted quite low and is completely exposed. When driving on the motorway I hit what looked like part of a bumper which clattered about underneath the van as I passed over it. Whether this was the cause of the damage or not I can't be sure. However there is a chip about the size of a 5p piece taken out of the bottom corner of the tank. As a temp measure I have covered it with some gaffer tape, but with it being the corner it hasn't taken that well. The tank appears to be made out of some sort of hard plastic. Can anyone recommend a decent plastic repair kit, preferably one that doesn't involve welding although if that's the best method I will give it a go. On the plus side, I wont have to empty the grey waste, until its fixed as it will be permanently empty (joke)

 

[donkey]

Having looked at the last photo from OP, I am not sure any of these adhesive/sealer products are needed. It looks like a round hole into which something was fitted. So is it threaded?
If so you need to find a bung to fit.
If not, it needs a suitable tap to thread the hole, then simply screw in a bung. Job done.
There is virtually no pressure in the tank so does not have to be super sealed, a threaded bung hand tight would seal it.

Geoff

 

[GeoffC]

Weirdly, the exact same type of hole is present on the opposite corner of the tank as well. I'm now beginning to suspect tampering/theft. Im struggling to believe that this has coincidentally occurred with both bungs or whatever was there. I'm wondering if something has gone on last month when it was up on ramps for the MOT. I have now glued into place to new rubber bungs using NoNails Waterproof glue as per the pics. This will allow me to get them out if needed in the future. I'm slightly concerned that the bit of plastic I'm looking at is actually a cover over the tank as opposed to the tank itself. I'm fairly certain it's not an overflow as the water came out of an empty tank when I was showering. I'm probably only going to know now when I use the van again