What should I do with the pipe gauges?

Hint 1 of 9:

Did you click on them?  The man was obviously here.  The gauges must be
important.

Hint 2 of 9:

Notice that one gauge, at the very bottom, never changes no matter what you
do with the wheels.

Hint 3 of 9:

Your object is to set the other four to match what is set on the bottom
gauge.

Hint 4 of 9:

Notice that multiple gauges will sometimes move when you turn a single wheel.

Hint 5 of 9:

But that's only if one gauge isn't already all the way to the left or right. 
You can often move just one of those gauges by turning a wheel until the
other one in the pair stops -- just keep turning the wheel.