Well I figured out the locations the water lines and drain line. Yes I said drain line. I have decided to omit the second sink. Why you say? Well as I stood and looked at the staked out layout of the kitchen I had a realization. Why do I need 2 sinks outside? I have a sink inside the house and a sink outside should be just fine. So with that thought in mind I nixed the second sink. I am however going to add a hose valve spigot on the outside of the wall of the corner counter on the right side instead of the sink. I will also be running a water line and adding another hose valve spigot in the area between the smokehouse and the hot tub.
You can see in the picture that I’ve laid out where all of the water lines and drain lines will go in red. I haven’t dug them deep at all because I only need the trenches dug down just deep enough so that the drain can maintain a descending angle of 1/4 inch over 4 feet. Our frost line is very shallow here. I have some irrigation lines in my hard that are in places only a couple of inches deep and they have never frozen. Now if you are building in a colder area and you are using water lines make sure to insulate them and install them below the frost line. The last thing you would want is to have a water line freeze and burst underneath you floor.
My plan is to add a tee (T) to the drain pipe under the sink in the inside kitchen from the sink in the outdoor kitchen. That way I can use the same drain pipe without having to add more. If you were building a kitchen in an open area or an area away from any drains I would think that you could treat the water from the sink as grey water and run your drain to trees, bushes or other plants that you anted to water. If you do that just keep in mind not to put anything down the drain that would hurt the plants.
I have also spent time at my local home improvement store and I have decided to use PEX tubing for the hot and cold water. I can buy the tubing in roles of 100 feet for about $27.00 US as opposed to about $20.00 US for 10 feet of copper tubing. Since keeping costs down to a minimum is part of my focus I decided that the PEX tubing is the most economical option. I will admit however that I would prefer copper and that I would use it if I had the extra money. For the money the best option does seem to be PEX tubing and since it is rated for both indoor and in ground that should work. One word of caution about PEX tubing. It is sensitive to UV (Ultraviolet Light) light. So you can’t use the PEX tubing in a place where it would be exposed to sunlight. So you run the PEX tubing inside walls, under your house, under the kitchen floor in the ground or even up inside the counters but, you have to attach and convert to a solid pipe, like a short piece of copper, that can be exposed to sunlight and the elements anywhere you want to have a hose valve spigot or any other exposed fixture or connection.
I have seen other people use PVC, CPVC, steel pipe, and even the black poly irrigation pipe. You can use whatever you want and whatever is available to you. For reasons of cost and availability I chose to go with the PEX tubing but, you can choose anything that works for you.