Rain water....it's perfect, shorten a downspout from a rain gutter , and let it fall into a rain barrel, it will settle after a rain, and the soft pure rain water is ideal for enemas.
If you live in an area where rain is frequent, and the area it's falling on is clean from rain, try attaching a rubber garden hose to the downspout about head height, and then,...... just stand in the rain...... naked , or if not completley private, wear a long tee shirt , nake from the waist down, then insert the male end of the garden hose ( it's brass and smooth ) into your rectum, for a refreshing outdoor natural enema experience. Don't worry, you can't take more than your body will allow, and when "full" the enema will release and expel on it's own and continually flush out your colon. the wetness will induce your body to urinate naturally during the enema, you won't even notice when it happens .....accept for the feeling of relief.
The wet tee shirt , the body, dripping from head to toe, and rinsed in a fresh rain, colon flushed with soft rainwater,.....nice