Most flugels are built with a adjustable leadpipe which is connected
to the first valve. If we look at the distance from the mp to the first
waterclef, it is pretty equal to what the distance is on a trumpet with
the exception that on the flugel, the air (and moist) has to go through
the valvesection before it arrives the waterclef area.
What I have experienced with the flugels I have played (and own(ed)),
Besson Sovereign, Getzen Eterna 4V, Couesnon Monopole, ConnV1
and Taylor Phat Boy, is that the water is no problem on valve 1 and 2
due to the short distance from the mp. Valve 3 collects some water,
but most goes through the valvesystem and has to be emptied through the
main waterclef after the valvesection.
My experience tells me that a waterclef before the valvesection would not
have any practical use.
Things that can get a valve to hang up could be that there is sharp edges (see picture)
which can make the valves hang up. It is possible to use very fine emery paper
to (carefully) grind off these sharp edges by placing the emery on a plane surface
and rotate the valve a couple of revolutions.
(I used this method on the Sovereign 947 each time the valves started to make
a "scratching" feeling.)
Clean the valves well and use a synthetic oil.