RWB Water Valve
I thought of something that may be civil engineering, emergency housing, and reprap related - or maybe not.
Water valves/manifolds for 55 gallon drum emergency/low tech water supplies. The majority of the 55 gallon type water supplies that I have seen have a metal outdoor faucet welded into the side of them with a hose pipe connected to them for bathing, washing, and I guess drinking water. The $15 (USD) metal faucet could be replaced with a reprap made plastic ball valve, a reprap plastic hole insert, two neoprene washers, a reprapped securing nut, and some waterproof sealant. You would still need to a drill a hole in the side of the barrel, but that's cheaper than welding - and a large punch and sledgehammer would work in a pinch to make the hole.
Another option would be to join multiple barrels together and have a reprapped manifold that fed multiple hoses to multiple places (I'm thinking along the lines of a tent city arrangement). The last manifold I put in was several years ago, it was brass, cost around $150 (USD) and my thought then was "why isn't this thing made out of plastic, it would be cheaper."