I can think of a couple possible reasons.
If it's opened all of the way, you can only turn it one way to loosen
it, and you lose the old, tighten it first before trying to back it
Depending on the faucet, maybe the packing would be squeezed and take
a set, then when you tried to close the valve it wouldn't hold.
On Sat, 11 Sep 2010 12:09:01 -0700 (PDT), Higgs Boson
Look up valve backseat on google.
I was a boilerman in the Navy and it was our practice to fully open a
glove valve, then crank back down a quarter turn.
If you didn't do that it could take much more force to close it later.
Maybe corrosion sticking the disk to the backseat or maybe pressure
equalization, can't remember if I ever knew.
Gate valves were just fully opened or closed.
This was 1500 psi steam or water.
Never had significant packing leaks from not backseating.
I still do the same with faucets out of habit.
Before I repacked it I had an old garden faucet that leaked less
through the packing when I backedseated it.
Don't think it really matters with common faucets.
Somebody already gave the best reason for backing them down - so you
don't get caught turning the wrong way.
I would assume it has to do with compressing the packing and
eventually causing it to leak. I wouldn't worry about it unless you're
in the habit of torquing it open pretty hard.
But then you should probably wait to hear from someone who knows
Granted, this is just another "I've always heard" answer but this is
why I've always heard you do it:
If the valve ever gets frozen due to rust, you have no wiggle room -
literally. If it's all the way up against the stop and it won't turn
towards close, you can't turn it the other way to try and break the
Not a good situation when you are trying to close a house main in an
I've done it twice this weekend already. Replaced the innards of my
kitchen faucet and replaced a toilet. Both shutoffs were left about a
1/4 turn towards closed.
When I was a kid (quoting Moses, or Aristotle, or my Dad, one of
these.) We backed off half a turn. The next guy might not know if the
fuacet was on or off. Might not know right or left. But, if the faucet
is all the way open minus half tun. If he turns the faucet the wrong
way, it's got half a turn of travel. So, the next guy knows it's not
locked up shaft. Anyhow, that's worked well for me.
My condolences to the poster whose inlaws crank valves tight enough to
crush the faucet washer. That's no fun.
I have no idea, I've never heard that one before.
However, my in-laws were apparently taught to turn a valve OFF you have to
cinch it down as tight as humanly possible. :) Before we upgraded their
faucets, I had to constantly replace the rubber seals they had completely
compressed to the point they wouldn't seal anymore.
You go, limey! We don't know what the hell our government is telling
us. For just one example, take the Environmental Pollution Agency.
Maybe tsome things are slightly better under Obama, but it will take
forever, if even possible, to repair the damage caused by the Bush
(and preceding Reps) robber barons.
Note that the REAL "robber barons" of old were cruel, mercenary,
corrupt, etc.etc. but at least they LEFT us something tangible -- like
Libraries, Foundations, Railroads, great Buildings, and othe useful
assets. Not this Wall Street crowd; it's just a giant casino,
and screw the Pee-pul. Capitalism is a better system than any other
(given the fallibility of human nature as shown by the repeated
failures of idealistic societies) but it has to be run on a moral
foundation or we end up like we are. How come some wildly successful
capitalists manage to give back to the society? (a) because they get
tax breaks and (b) because they think it's morally right to "give
If the valve has been open fully (months/years) it may be hard to
close. Also, breaking it loose when fully open can take some of the
stem packing with it. (Stem may leak unless fully open/closed)
An example is a toilet or sink shut-off.
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