I made a quick drawing on where to place an extra t and ball valve for flushing the water to prevent tds creep.
After its plumbed, when you start making water just open the valve and allow the water to drain for a couple of minutes than close the valve and continue on like normal. This flushes the water that's been sitting in the prefilters and membrane, lowering the initial start yp tds goning into your di resin.
I do this in addition to the manual flush kit