The ten things
The short version. Each one is explained on ten things you can do this weekend.
Fat jar by the cooker. Strainer in the sink. Bin beside the loo, and only the 3Ps flushed. Old medicines back to the pharmacy. Leaky loo checked. Water butt on the downpipe. Car washed on grass, gravel or at the car wash. Four days out of the river after flea treatment. Dog poo bagged and binned. The app and the hotline (0800 80 70 60) on your phone.
Never down any drain, sink or loo
The consolidated list. If it is on this list, it goes in the bin, to the pharmacy, or to the recycling centre; never down the drain 25 29 30 26.
Never down the sink: cooking fat, oil and grease; food scraps; paint; white spirit and solvents; engine oil; medicines; garden chemicals.
Never down the loo: wet wipes (including "flushable" ones); period products; nappies; cotton buds; dental floss; contact lenses; plasters; razor blades; medicines; anything that is not pee, poo or paper.
Never down an outside drain or road gully: anything at all except rain. Outside drains usually lead straight to a stream or the river, untreated 13 16.
And if you are on a septic tank: all of the above, plus go gently with bleach and antibacterial products, because your tank is alive 25.