replace water cutoff valve for sink?

How hard it is to obtain and replace a new water cutoff valve for under the sink? I was advised here to replace my ancient one with soft gaskets to a modern ball valve or something... is it available at home depot type place or must I chase down an inconvenient plumbing supply place?
Reason for my interest is I noticed the valve is sort of screwed on (compre ssion ring?) rather then soldiered... at least there is a 1 inch nut on the back before it disappears into the wall. So with the water main turned off , should I be able to wrench it off and stick on a new one with a bit of pl umbers tape?
thanks
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On Thu, 15 Aug 2013 01:18:06 -0700 (PDT), dumbstruck

Readily available at any home improvement store. You have to be sure it is the same size, not smaller or it will not fit in between the existing pipes, unless there is room to move them.
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On Thursday, August 15, 2013 5:59:25 AM UTC-4, Ed Pawlowski wrote:

a modern ball valve or something... is it available at home depot type pla ce or must I chase down an inconvenient plumbing supply place?

the back before it disappears into the wall. So with the water main turned off, should I be able to wrench it off and stick on a new one with a bit of plumbers tape?

Yes, they are readily available. But unless the existing one is causing a problem, eg leaking, or you're changing the faucets, why look for trouble where there is none?
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On Thursday, August 15, 2013 4:18:06 AM UTC-4, dumbstruck wrote:

a modern ball valve or something... is it available at home depot type plac e or must I chase down an inconvenient plumbing supply place?

he back before it disappears into the wall. So with the water main turned o ff, should I be able to wrench it off and stick on a new one with a bit of plumbers tape?
No plumbers tape. Where did you get that asinine idea?
Plumbers tape is for threaded connections. Compression fittings don't need it, and can't use it anyway.
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Ideally, you shut off the water, and open all the faucets in the house. Drain the lines. Use a crescent wrench to unthread the pipe that goes to the sink faucet. Next, Using two pipe wrenches, one is used to hold the existing pipe, and the other unthreads the shutoff. Probably a half inch pipe thread. And the other pipe is probably 3/8 compression. Take the shutoff to HD, buy two. So you can do both the hot and cold.
Buy also teflon tape, Rectorseal #5, and a wire brush. Wire brush the external rusty pipe threads, to clean them up. Wrap the external threads with teflon tape, and then dope them up with Rectorseal.
Using two pipe wrenches, put the new shutoff on. Crescent wrench, put the pipe to the sink on.
Shut off all the faucets, and turn on the water main, very slightly. Check for leaks. Go around and burp the air out of all the faucets.
In the real world, the pipe breaks, you have to call a plumber. He comes and takes out a couple feet of drywall with a sawzall so he can work. Job runs late, charges overtime. Lights the wall on fire with his torch, the FD comes out to put it out. And sends you a bill, as they are not municipal department. And then the drywall guy has to come out on Saturday and charges you double time to fix the wall the plumber took out. The fire restoration company gets a couple hundred bucks to blow out the smoke, and deodorize.
. Christopher A. Young Learn about Jesus www.lds.org .
On 8/15/2013 4:18 AM, dumbstruck wrote:

cutoff valve for under the sink? I was advised here
to replace my ancient one with soft gaskets to a
modern ball valve or something... is it available
at home depot type place or must I chase down an
inconvenient plumbing supply place?

sort of screwed on (compression ring?) rather then
soldiered... at least there is a 1 inch nut on the
back before it disappears into the wall. So with the
water main turned off, should I be able to wrench it
off and stick on a new one with a bit of plumbers tape?

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He's got compression fittings, not the screw on kind you are describing.
On Thu, 15 Aug 2013 08:27:00 -0400, Stormin Mormon

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On 08/15/2013 01:18 AM, dumbstruck wrote:

They are readily available at every big box/hardware/plumbing store, but you may very well be opening up a big can of worms by replacing it for no good reason.
If it isn't leaking and it still works, leave it alone.
Jon
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The OP actually said "I was advised here" to replace it.
If "here" means a.h.r, then there is no need to question "why". He should just replace it because, as we all know, no bad advice is ever offered in a.h.r.
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On Thu, 15 Aug 2013 01:18:06 -0700 (PDT), dumbstruck

When you get to replacing the old one, don't try to pull the compression "ball" off the pipe. Just reuse the old ball and nut if you can, it's already squished itself into the pipe and if you manage to pull it off you may not be able to get the new ball to seal and then you'll have to solder on an extension or switch to a soldered on valve. And don't get carried away tightening the thing more then you need to stop it from leaking, no sense in over crushing teh "compression" part of things.
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