WM Valves, the self-cutting variety, do they deteriorate?

[L_Plate]

Do those washing machine valves that cut their own holes into the copper pipe deteriorate over time? My washing macine is taking ages to fill so I have disconnected the hoses at the WM end, held hose outlets over a bowl, opened taps and hey presto...very little happens ie a small amount of water dribbles out into bowl. I heard somewhere that the disc of copper that is cut can sometimes block the water but having remoced the valve I can see no evidence of this and the machine was always fine in the past. Is it that they become scaled up? Should I replace them with new ones or change to the more conventional ball-o-fix WM valves?

Thanks for any advice.

 

[kevplumb]

self cutting taps are always crap for flow

change them and do the job properly

 

[Slugbabydotcom]

Those self cutting valves are the same as these

 

[L_Plate]

Thanks for the replies guys. Very interesting link Sluggy_B.