I think it's better to have it closer to the pump as you say, but if under the sink is the only place, then my guess is, it will work just fine. Normally you just put a "T" on top of the tank, then pass the cold water thru the T. Personally I would try and put it past the Water Heater inlet. The Water Heater kind of acts as it's own accumulator tank. This way you're getting the most bang for your tank.....at least that the way I see it. I acquired a real neat little 1 gallon(1/2 gallon net) accumulator tank that I think would be perfect. I haven't figured a good place for it yet. Currently I have the SureFlo plastic unit that works fine.