The top hose connection is for winterizing. Connect a hose and stick the other end in the RV antifreeze container.
The middle hose connection is used to fill the fresh water tank AND to run exclusively from shore water, via the garden hose.
The bottom hose connection is the black tank flush.
Going back to the middle hose connection.
The bottom valve is used to switch between filling the fresh water tank and running off the garden hose. When filling the fresh water tank, flip it to "fill". If I want to run only from the shore water garden hose, I flip the valve to Normal Flow.
The middle valve is used for Winterizing. When winterizing, the hose is connected to the top hose connection with the other end of the attached hose in the container of RV antifreeze (Pink Stuff). Turn on the water pump and "pump the pink."
The top valve is the water heater by-pass. When you don't want any water to go into the water heater tank, you flip this to on. It can be flipped on or off and does not affect water flow. However, with it "on", you will not get hot water, as the water heater is by-passed.
To run water from the garden hose, that bottom valve needs to be in the Normal Flow position and the spigot at shore water turned on. The camper on-board water pump is turned off completely. Water heater by-pass is in the winterize valve is in the off position.
To fill the fresh water tank, flip that bottom valve to "Fill" until the tank is full, or as much as you want. After the tank is full, flip this valve back to "Normal Flow". Otherwise, your water pump will cycle on and off periodically. Remember to turn your water pump "on".
Here's a couple more really slick things you can do.
To run your black tank flusher when you don't have garden hose to hook up, which happens to me at dump stations, because the wet-bay is so far forward of the camper, and the dump valves are in the middle. Most dump stations don't even have hoses any more, they've been removed, or are simply too short.
Hook up the blue hose from the shower directly into your hose connection for the black tank flusher. Make sure your water pump is "on". And then simply turn on the shower knobs. Water is pulled from your fresh water tank and will flush out the black tank. Remember, there's a check valve in the black tank flusher line, so no threat of cross contamination. I do this all the time. I never flush with the garden hose.
Next great thing?
When winterizing, do the same thing to run antifreeze to the black tank flush line. Once antifreeze starts dripping from the black tank outlet, you know the lines are done.
What happens if your water heater were to go out completely and you have nothing but cold water, and you really, really want a quick shower? Simple! Heat water on the gas stove, pour in a bucket. Take the bucket and set up the valves for winterizing. Attach your winterizing hose, flip the water heater by-pass valve so nothing goes into the water heater tank, turn on your water pump, and start pumping the HOT water from the bucket. Go take your shower. Granted, it WILL be short, but you can do this if you are desperate. hint, use only the hot, or the cold on the shower. There's not much water in the bucket and it has to pump through the lines. If it pumps through 2 lines, you'll run out of hot water much faster. I won't be "too hot" either, as it will cool coming through the lines. I've actually done this before and it does work great!
Need to wash the front cap of your camper because it's bug covered and you are on a campsite with no water hook up? Simple, attach a garden hose to the shower (blue hose), turn on the shower, and you can spray anywhere on your camper and wash it! I've done this many, many times.
One final word of advise.... If you flip the winterizing valve with your water pump on, THINKING you flipped the valve from fill to normal run, your water pump will run and run and run, and your faucets will spit air and a bit of water. OH DUH! You flipped the wrong switch .... I know... I did that just last week!
Good luck, hope this helps.