Dialysing tank design

I am wanting someone to design for me a small tank or chamber that can be used for dialysing a solution against running water. What i am wanting to do is to dialyses a liquid solution against running water to remove some chemical additives. The liquid to be dialysed will be contained with conventional dialysis tubing (eg [login to view URL] 20k MW cutoff). I built a unit myself from a plastic drum i got at a hardware store. For this project though i am thinking of either a polypropylene tub or possibly plans for a stainless steel water-bath type unit. The dialysis unit would need to be able to maintain a constant water level, be very simple design with no moving parts, have some shelving for lying the tubing sacks onto. I am thinking of a 50cm long x 30cm high x 30cm wide tank with an inlet for running water at the top and a tap to allow the water out at a constant height. Consideration needs to be made as to how the water would flow through the tank, if this is not right then parts of the tank might not get the water moving past correctly and the dialysis process might not work so well. I want to be able to dialyse about 1 to 5 litres of solution each time. The tubing i think holds about 5mL per cm. I expect it may take 48 hours to dialyse fully against running water. There may be units that you can buy already for this type of thing - I don't know. I am open to suggestion as to what is the best way to make this type of thing. I want the unit to be able to sit on a bench top.