Fresh water tank leak

Sikaflex .... sticks like the proverbial to a blanket

Yep, Sikaflex 291 is intended for marine applications and will be good for vibration resistant joints. 

Thank you both.

I had a problem with the jubilee clip that had rusted to the pipe that attaches to the outlet of the freshwater tank.

The plate protecting the connection from the splash off the road did not allow the leaking water from where the jubilee clip had rusted and wasn't stopping the leak, was then unable to escape downwards. It then welled up and escaped into the van at the point where it could escape. Hence damp inside the van!

Sukafelx and a new jubilee clip has done the job hopefully.

Is it at the junction elbow to the tank  or in the pipe?Mine has a pull off  elbow which gets a bit loose and PTFE tape sorts that out.If you have the blue  ribbed tubing onto the tank that can develop cracks as the plastic degrades and can easily be replaced with a new piece and new jubilee clips.I take it that we are talking about an underslung CAK  type tank and not an inboard type?

I used PTFE rather than Sikaflex because I can easily remove the elbow to back flush the tank then,to clean accumulated  sand etc out of it.