the arrow indicates the direction of flow, if you put it on the wrong way the water could push the jumper closed, depending on the type of stopcock...

a stopcock is pretty much like a regular tap in construction, water goes in through one end, passes through the valve, and out the other end, but it doesnt go straight through like it would in a gate valve for example, it goes through in an S shape, in-up(through the jumper seating)-turn-out, if it was fitted the wrong way it would go in-turn-past the "tap washer"(pushing it onto the seating) and no further. Most stopcocks have jumpers that are attached via a thread to the handle so that it will hold the jumper up(open) whether the water is pushing against it or not, it still causes extra stress on the stopcock though.

Imagine the outlet on this pic comes from the side and not the bottom...




IN--->--->OUT
btk

funnly enough, found and replaced a stop cock in my cornwall "holiday" because it forced the washer to come away and lodge onto the seating

probrably also why it constantly leaked from the top of the tap spindal even after packing it out?

ss

lol, says the only gay plumber on the forum  

ss

lol btk, i were talking about StopCocknot gay cock

all that talk of fitting the cock into the pipe the wrong way and stuffing something round the shaft to stop it leaking got you seeing subliminal meanings in an inocent topic ay!

don't worry btk, theres a whole sociaty out there!!!

lol

ss