In this months Saga mag.. A gadget called drought plug is mentioned [P101].
Do any of you clever people think it looks O.K?
I know a few people who have tried one & have had problems getting a good seal, once the issues with the seal have been resolved the syphon effect can be difficult to get started & flow is very slow.
Exterior greywater diverter valves are more popular around here, they are simple to fit & if you run out of storage for the greywater then you can easily close the valve so the water goes down the drain instead.
http://www.reuk.co.uk/buy-WATER-TWO.htm
One should challenge your water authority for reduced charges if one reuses waste water & not discharge into the sewer.
Thames will discount your bill if you have 'soakaways' (not much but every little helps).
As Thames have raised bills YET AGAIN, you have to give as good as you get!