Did a search a while back, and came across Rich's diy D I unit with pics.
As we live in a soft water area, and concerned about the amount of waste water from our R O unit, we thought we would give it a try.
We went out and bought a 15 litre bin for £3.99 and with a bit of tubing that we already had, knocked up this little unit( well, my mate Dave the professor did) and it works a treat.
It took a while to get the flow about right, but it turns out about 20 litres an hour and no waste! Dont know how long the resin in the bin will last, will let you know.
Thanks again Rich for a cracking idea
Regards...Jake.....Westclean