Hi I live in Essex and water here straight out of the tap is 470. When I got a new 40/40 Ro (about 13 months ago) it was taking the water down to 025 before it was going through the resin . Now it's up 034 before going through the d.i is this normal? As i'm having to change the resin nearly every month now as it shoots up a lot quicker. From 470 t0 034 is still roughly about about 93% so is it worth getting a bigger d.i or even two of them? Any advise would be great thanks.