First off, I need to ask a couple questions:

1. What kind of pipe are you working with? Galvanized Iron pipe? copper Pipe? CPVC tubing or a PEX system?

2. How far are the existing valves from the wall?

3. Are you on a slab or over a basement or crawlspace?

copper pipe ... the back of most of valves are about 3/4" away from the wall ... on a slab

Thanks,

-Mike

About two years ago, I had a licensed plumber replace all my el-cheapo local shut-offs (contractor crap) with 1/4-turn ball valves and SS braided lines. I would have done myself except the the copper-tube stubs were so close to the walls I was afraid of making errors that would require tearing into the walls to remedy so I thought better to let a pro do it. If I had more time and experience, I would have undertaken myself. The valves he used are Dahl Mini-ball, made in Canada. I don't know about the competition but the ones I have are more-or-less perfect. Among sinks and toilets, I now have nine of them.

There are basically three methods used to mount the angle stop valves.
1. Solder type
2. 1/2"NPT Thread mount
3. 5/8" compression mount.

In new construction the angle stops are generally installed during the final trim out phase of the plumbing, which generally occurs after the painting or wall finishing phase.
At this stage there is a very high risk of causing damage to the wall finish if we were to install the solder on type or to solder a thread adapter on the stub out. For this reason most plumbers elect to use the 5/8" compression type which only requires a simple mechanical connection.

To install the compression type angle stops the stub out is cut to the desired length, then the compression nut is slide on the stub out, followed by the brass ferrule and finally the valve is slipped on. With the valve held firmly in its final location, the ferrule and compression nut is then slide out to the valve and tightened finger tight. Once the compression nut is finger tight the plumber uses two wrenches, one to hold the valve steady while the second wrench is used to tighten the compression nut. As the compression nut is tightened the inner brass ferrule is slightly compressed into the wall of the copper pipe thereby locking it firmly in place.

When changing compression mount angle stops many people make the mistake of attempting to pull the ferrule and old nut off the copper stub out and usually in doing so they distort the shape of the copper making it very difficult to get a tight seal with the new nut and ferrule.

A much simpler and more reliable method is to unscrew the compression nut then slide the old valve off the copper pipe leaving the original ferrule and compression nut on the pipe. You then remove the compression nut and ferrule from the new valve and slide the new valve on the pipe, tightening it in place with the original nut. While this method does not work 100% of the time, as a rule it will work most of the time and certainly bears trying before you begin cutting the pipe or trying to remove the old ferrule.

When tightening the compression nut you can use a pair of channel locks to hold the valve steady, but when doing so be sure to pad the valve with a rag first so the teeth of the channel locks does not scratch the finish. I find an open end wrench to most convenient to tighten the nuts in a tight space. (I especially prefer my Craftsman ratcheting open end wrench.)

When selecting angle stop valves I use the solid brass 1/4 turn ball valves exclusively. The ball valves have the advantage that they are quick acting full bore valves and they are also have the advantage that when turned they are self cleaning which is a distinct advantage in areas where mineral scale builds up on internal valve parts.

I will probably open a real can of worms here, but My first choice of supply lines is chrome plated brass tubing with the cone washers that come supplied in your faucet set and the compression nut and ferrule that comes supplied with your new angle stops. I have seen copper or brass tubing supply lines that have been in continuous service in commercial applications for 20 or 30 years and they still work fine.

My absolute last choice would be the stainless steel brain lines. While the stainless steel braid gives the illusion of being some kind of high tech space age strength and durability in the final analysis many of those lines are the absolute weakest link of all the choices. It is true that the stainless steel braid will prevent a line from blowing out, but when we consider that the maximum allowable line pressure is 85psig, the chances of any lines actually blowing out is slim to none. On the other hand, what most people don't know is that a vast majority of those stainless steel braid lines has nothing more than a stainless steel braid over a cheap neoprene hose. Under certain water conditions neoprene has a relatively short service life as is evidence by the failure rate of neoprene toilet flapper valves.

In regions where they have problems with the water deteriorating the neoprene I prefer to use chrome plated brass lines with the factory preformed cone washers that are made out of nylon.

Thanks ... I will look into buying a 15/16" ratcheting open end wrench. This is the size of all my compression nuts.

I really had trouble getting enough torque to crack the nut off last time I attempted this ... these fittings are around 35 years old.

Would "Liquid Wrench" be a good option or do I need to heat the nut with a torch for awhile first. Any tips on what method works best for really stuck nuts in these situations?