Just to add my bit , for a long time now i have been saving myself a small fortune on resin , i am DI only with a TDS of about 100 , i used to buy a bag every month , i now get one every 3 months , and the sophisticated piece of equipment i use cost me £3.49 !
All that is needed is a 10 litre swing bin and two elbows .
The water is constantly fed from bottem left of bin to top right of bin , then into holding tank , the slower you can get the flow the longer the resin will last.
1st Pic , the bin , 2nd Pic , the flow rate .
Rich P @ F