Washroom sink waste

Hi All. Posted this on the Facebook a couple of weeks age site but got nowt... [u]Is it possible for waste pipe to shrink over the winter? Rinsing through the system today and noticed a leak under the sink in the bathroom. I seriously wonder how it hasn't leaked before as the pipe is cut so short. Still just about reaches the connector and I've removed the bracket securing it at the back... any suggestions?

Since then I tried a couple of different things. I've bought more waste pipe with the plan of joining in a piece to extend the pipe but cant get a suitably sized coupler (26mm) to join the 2 ends. Reluctant to start replacing the full length of waste pipe. Outside my current skill set

I tried to attached a couple of pics to this post but haven't been able to... or have I???.

Any advice

Yes the pipe can get stiff/ brittle and shorten over time , as Killiand suggested it may have gotten pulled , can you follow the pipe to the wast tank , where is the tank fitted under on the outside ,something may have caught onto it or inside a cupboard something may be sitting on the pipe.
to join two pieces together I heated the ends with hot water and inserted about 200mm of 20 mm pipe coated with sealer.
I have had to move around some of the pipes under the van but before I did I disconnected them from the tank and blocked the ends with a cork ,then filled them with hot water to soften them.

Not sure on your pipe size as it is not one I have heard of
Anyway have a look on
https://www.caravanaccessorysh…ttings/275
I would guess that will have what you are looking for.
If you have a motorhome/caravan dealer near you and they have workshops they will also have them (But maybe not in the accessory shop)
David