Our super cheap, dog bowl camper sink.
We spent several trips pouring water out of bottles, spilling water inside the car, then having to get out in the rain to pour it. So we finally decided that we really wanted a tap. It seemed silly to have a tap without a sink, but we were very limited for space and nothing commercially available seemed to do the job. So we made our own, in the end it came to around £40 for the pump, sink, tap and all the piping. It serves it's purpose extremely well and we are very pleased with it.
From the outset we were clear about what we wanted from our sink and tap. The tap was more important, and the sink only really needed to be capable of catching drips and draining pasta or cleaning teeth. We were not planning to use it for washing up. We wash up in a plastic bowl which we do on the fold down table on the rear door, outside the vehicle. This set us free to use a small sink. In my search for donor bowls we examined many different options but settled on a dog bowl, which was bought for £2. All we did was cut a hole in the bottom and add a plughole from a caravan shop, which cost £8. We opted for one with a 90 degree angle on the waste pipe to save some space. The waste pipe came from an old washing machine, and fit perfectly (after I washed it out a bit). Total for the sink was £10.
Fitting the sink was somewhat of a battle as the side boxes were already installed in the vehicle. But using a drill and a jigsaw it eventually went in the hole. We stuck it down and sealed around it with silicone. The waste pipe exits the vehicle via the factory rubber grommet behind the water tank. It can be run into a waste tank that we just put on the ground under the car.
The tap was a whale swivel faucet we bought from a chandlery (boat shop) for about a tenner. I would definitely advise looking in chandleries for camper stuff as we found boat components can be smaller and better built than those made for caravans. We twinned it with a waterproof momentary push switch, both mounted on a piece of metal that we scavenged from an old coat hook thing. The water pump is a base model, whale submersible pump which we got off the internet, again for about a tenner. It has a flow rate of 10L a minute and gives really good water pressure. More than adequate for our purposes. The pump just sits in the water tank (details on another post) below and sends water out the tap when the button is pressed. Make sure to use food grade piping as other plastics are not suitable for drinking water. The jubilee clip on the pump is also marine grade so it doesn't rust and contaminate our drinking water. The power to the pump runs off our leisure battery and it's earthed on the old seat mounting bolt, behind the tank.
All in all it was a great little addition to the setup. Reducing the amount we need to move around while cooking and reducing the amount we need to open the doors when cooking in the rain (Something we do a lot when chasing windsurfing conditions). We are a little limited by the small water tank (max 15L), but this is still way more than we would use in a single day, so we simply top it up from other tanks. Our bed width and desire to have the tap and cooker on the same side, limited the size of the tank. But on balance I am happy we sacrificed the capacity to gain the functionality of the cooking and water supply being close together. I hope this shows that a sink and tap need not be expensive or take up vast amounts of space, thanks to a little lateral thinking!
Update: we have since made a special water tank for it, details in another post.