Thanks 4 the replys - Anyway as they are already due a change, whilst i was ordering a new 40" RO and a few sets of 20" pre - filters from gaps water, i spoke to the always helpful gill about the spectrum di resin vessel thing, and funny enough although they sell them, she dosent appear to really rate them either, as they are very awkward to fill and empty, as said above, so i think i will stick with the basic 6.9l one i already have. I also asked her about the water travel direction within the vessel (up or down), and she says a few of her customers reckon swapping the water inlet for the outlet, makes the resin last a little longer? as although it isn't the factory instructions, it would mean that water travels down the riser instead of up it, and the downward water pressure disturbing the vessel's unused base resin? kind of like what i was thinking in a way, just a idea i guess, and will give it a try. Cheers m