I'm a little embarrassed at posting this - shows I'm a bit sad. I've discovered that the ribbed plastic hose that I use to connect between the outlet of the van and the grey water container fits neatly into the smaller sized standard domestic waste fittings. I used Marley fittings from B&Q. My device greatly speeds up connection to waste, doesn't fall off the outlet and does not impede flow. You need two T-shaped push-fit fittings, some straight pipe and an end stop. I used 2 very short lengths, about 2 inches, of the grey hose. I pushed these into the bottom of each T. The tops of the Ts' are then connected together using straight pipe so that the two pieces of grey hose aligns with the two outlets from the caravan. I then fitted a stop to one end and more grey hose of sufficient length to connect to the waste container into the other. I find it works really well. Not a bad improvement for about £2 and 20mins work.