On Thursday, July 19, 2012 8:25:51 PM UTC-7, (unknown) wrote:
I have a Watts single handle washing machine valve that was installed
by a plumber less than 5 1/2 years ago, and I only did the laundry
once a week or sometimes not for 2 or 3 weeks. Tonight it developed
a leak when doing the laundry. The leak was at the stem (handle). I
went to Home Depot and bought a new Watts valve for $29 and just
replaced the whole thing (including the O rings) except that I reused
the old elbow attachments since those were soldered on.

The new valve appears to work fine, so far, and I am keeping fingers
crossed that it stays leak-free.

My question is this: When doing the laundry I would typically leave
the valve half-way (or less) between Off and On rather than all the
way On. When not doing the laundry the valve was off. Do you think
the new valve would be less likely to develop a leak if I turn it all
the way On rather than half-way-on (or less) on when doing the
laundry?

(I now have a pressure-reducing valve where the water comes into the
house, so maybe I don't need to bother with the midway position as a
means of reducing the water flow)

Thanks,

Jay

Since you took out the old valve, do you see any cavitation in it? Cavitation occurs at or near the point where the flow is restricted when partially closing the valve. The water when restricted will spray at a very high pressure and erode the area which is restricting its flow. Reducing the water pressure to the entire house or opening the valve all the way will reduce this problem but that in turn can cause other problems like less water pressure at the shower heads.