PUZZLE 008 Pipe Nightmare

Here is some very complicated pipework.
If you turn on the correct two valves out of the eight valves at the top, water will flow out of all of the exit pipes at the bottom.
If the pipe splits into two, the water will flow both ways, but only in a down-ward direction.
Touch a valve to select or deselect which pipe you will send the water down.
Figure out which two valves are the correct ones.

Hint 1

The correct two valves each send water down to four exits.
Follow the path of each pipe to see which exit it leads to.

Hint 2

Let's look at the exit pipe four away from the left.
There is only one pipe that leads here.
Follow the pipe up from the bottom to figure out which one it is.

Hint 3

Continuing on from hint two...
One part of the answer is E.
The water from the two pipes will flow to the exits without mixing with water from other pipes.

Super Hint

Continuing on from hint three...
Now let's look at the exit pipe two away from the left.
The pipes that lead to this exit are A and B.
One of those pipes leads to the exit on the far right.
That is the other part of the answer.

Answer for 'Pipe Nightmare'

The answer is 'B and E'.