Washbasin Nuevo 2008

The waste water from my bathroom basin takes ages to empty, I have tried Sink Unblocker fluids but none have worked so far.
Has anyone else solved this on a Nuevo?

It might be worth opening the swing shower door and unscrewing the 4 long screws (covered in sealant or plastic buttons). Take off the panel and you can then take off the pipe and put some wire down to unblock or clean it.

I had to do this as the pipe came loose on a journey, the water was draining onto to floor below the shower tray. I fitted a big jubilee clip on the pipe which I think A/S had missed.

They missed mine too Fred, with similar results!

Typical of A/S I fear. Cracking good vans in most ways, but spoiled by irritating little details.

(By "irritating little details" I was not specifically referring to the pillock who didn't bother to fit a jubilee clip because no one would know!!! But take it that way if you like.  )

It wouldn't apply to the swing wall basin, but I followed the kitchen sink drain on my Nuevo and found that it ran uphill. Now it runs downhill and so does the water!
Looking under mine yesterday at the resistors with corrosion screwed under the rear floor, I noticed that one of the shower drains runs down through the floor, under the chassis and then back up into the grey water tank. Then I looked at the electric heater pad on the grey water tank. What do you think I thought then?
The U bend in the shower tray drain will freeze in winter, so what's the point of heating the grey water if it never reaches the tank?
I pierced the bottom of the U bend with a small spike and let the water drip out. This will stop the pipe from getting blocked with frozen water. It will drip a little bit but hopefully so long as I am not in an immaculate drip-free zone no one will notice. Most of the water in the pipe will eventually reach the tank.

caraman and others:
If a drain runs downhill and then encounters a U bend, assuming it is not frozen, the static water in the U bend will slow down the flow of the water through it. It's logical if you think about it. My EK Nuevo kitchen sink drain ran down to behind one of the drawers, then sloped upwards before then running down one side of the oven and then through the floor to the tank. The part that sloped upwards acted as a U bend, containing some static water. Once I realigned the pipes to flow downwards all along their route the sink drained quickly.
This is by no means confined to AutoSleepers. I had a new Rapido which had the kitchen sink some distance from the tank. The route it took included seven right angled bends, and it was all in 25mm pipe. A right angle bend (an elbow, in plumbing parlance) has the same resistance to water or gas flow as one metre of straight pipe. I ripped it all out and replaced it with 32mm pipe, and reduced the number of bends to 3. The water then drained so fast it went with a schluuurrpp noise. What gets me is that the manufacturers could have done it if they had employed a plumber to design the plumbing, and it would even have cost them less because it used fewer parts and labour.

While you are there, observe the peculiar path of the drain pipes under the floor. One of them proceeds on its merry way towards the tank then turns round a 270 degree bend back on itself at a Y junction before carrying on round another U bend to the tank.
I don't like the way the grey water drain pipe runs much either. I don't like having to get my two hands under there, gripping the tap and un-clipping it from the terry clip and then needing two hands to turn the tap on and drain it. It is always covered in crud. The exhaust pipe is lower than the tap so if anything is going to crunch on the gorund it will be the exhaust. I am wondering if the grey water drain tap could be fixed and still have a fall from the tank to the tap. It could of course be electric . . . . . . . that would be another fault-prone gizmo that A/S could fit!
It wouldn't be too difficult to fit an electric solenoid to the drain pipe . . . .
https://www.ebay.co.uk/itm/Electric-Solenoid-Valve-for-Water-Air-Fuels-Normally-Closed-DC12V-24V-AC220V/282607178461?hash=item41ccb352ddmVm84ABEp96h22NGMgEq5CQ

Gassy, here is my electric drain thread. Bear with it, it’s long!

If A/S had fitted it then I’m sure it would have some kind of problem by now!!
Not blowing my own trumpet but it works brilliantly, that grey tap on its own was a major part of the flow restriction, how on earth can something as simple as that get through the design stage?

https://www.autosleeper-ownersforum.com/t30866-anyone-fitted-an-electric-waste-tank-valve

I have a problem with the sink draining to fast ,the plug won't stay put.

I have been working and unable to thank all of you who so kindly replied to me but I have some time off now so I will be able to try some of the remedies that you have posted.
I will post again when I solve the problem.
Thanks to all.