Symbol Plus Sink Drainage

After long wait, new 2023 Symbol Plus delivered from dealer beginning of June 2023. 2 days later filled kitchen sink with water ---- no drainage occurred at all! Bailed it out. Back to Autosleeper dealer. They spent a couple of hours "fixing" the problem! They say it's a "design fault! The waste pipe was routed over rear axle -- i.e. an uphill run to the waste tank --- so they re-routed it under the rear axle. Result: We now have trickle drainage from kitchen sink! When I complained about that, I was told by Autosleeper dealer that it was all to do with the outlet diameter & routage of the waste pipe, and nothing more could be done! I now carry a plunger to expedite emptying of the sink, which is the first time I have had to do this having owned numerous makes of motorhome & campervan over a 30 year period. Seems strange that a manufacturer with 60 years of build experience should expect owners to live with such a pathetic drainage system! Any suggestions to improve matters welcome!

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Yes, it does seem to be a problem - ours (2019) drains very slowly too, and I wondered whether it might be a bit clogged up, but the fact that your new one has the same issues may mean that I just need to learn to accept slow drainage!

I did try a plunger, which didn't make any real difference. Somebody elsewhere suggested that plungers on a small system like this were dangerous because the pressure could cause connectors to pop apart, so I may only try it when I have the waste tap open...

I cut 3 of the spokes out of the steel sink plug hole to make the exits of water a little faster , used a dremill with small cutter

Many thanks for the helpful replies. Looks like there is an underlying design problem. So much for their advertising boast of "60 years experience" building motorhomes & camper vans!