1/4 turn Ball Stop..Compression Fittings

[fred1949]

I think I bought the right shutt-offs but I thought I'd better write you & see. They both look the same except on is straight & one is on a angle. That part I understand but what I don't get is how they are labeled. They both are 3/8 COMP but one is 1/2" NOM COMPR inlet X & the other says 5/8 COMP INLET. They appear to fit a 1/2" copper pipe but like I said I wanted to check with you first. If you have any tips on a leak free installation any would greatly be appreciated.

Thank you so much you have saved my "bacon" so many times.

Fred

[LazyPup]

No problem Fred,

Copper pipe is measured by its inside diameter while copper tubing is measured by its outside diameter.

1/2" copper pipe is 1/2" ID but it is 5/8" outside diameter.

Normally compression fittings are only used on copper tubing so most compression fittings are rated by tubing sizes (OD), therefore if you desire a compression fitting to fit on 1/2" copper pipe (1/2"ID) you must use a 5/8" compression fitting (5/8" is the OD of a 1/2" copper pipe)

An angle stop or line stop valve is actually a transition fitting which joins the copper pipe in the walls to the copper tubing supply lines to your faucett or water closet tank. Quite often we see stop valves with the input listed as a "nominal" size.

The word "nominal" is indicating that the actual measured size is different than its rated size, which in this case it is rated to fit on a 1/2" copper pipe which is 1/2ID, but since the compression fitting must fit over the outer wall of the pipe, its actual measured size would be 5/8".

You will also see nominal sizing when examining PVC Pipe. PVC pipe is made in numerous grades or wall thicknesses to meet differing standards for temperature or pressure. While pipe is normally always sized by its inside diameter the must keep the outside wall diameter constant on PVC to interchange the fittings. In this case, in order to create a thick wall to meet higher standards the actual inside diameter will vary slightly. I.E. a 1/2" Schedule 40 PVC pipe will measure a true 1/2"ID, but a 1/2" schedule 80 PVC pipe will measure about 7/16ID to allow the thicher wall. The 1/2" schedule 80 pipe is then said to be 1/2" nominal, which means it is actually slightly undersized but it meets the trade standards for the volume and flow rate of a 1/2" pipe.

[fred1949]

Not being a plumber I think I understand what you wrote but just to make sure I do understand. Will these two shut-offs work with my 1/2 ridged copper pipe. Also my whole house is plumbed with this compression type fitting. Is this OK? If not what is the best type to use?

Thank you,
Fred

[LazyPup]

1/2" rigid copper pipe has an outside wall diameter of 5/8"

5/8" compression and 1/2" nominal compression fittings both have a 5/8" opening that fits directly on the 1/2" copper pipe so there is no problem there.

Stop valves are made in three styles, solder on type, thread type and compression type. They will all work equally well and in most instances it is simply a matter of choice by the installer.

Personally I prefer the compression type for a numerous reasons reasons.

1. You do not have the risk of damaging the finish wall with a soldering torch.

2. You do not need to install a thread adapter on the copper pipe before installing the valves like you would for the thread on type.

3. Compression type valves can easily be changed at a future date if the need arises.

Many people have problems when changing compression type valves because they try to get the old locknut and ferrule off the copper pipe. When changing a compression valve you simply unscrew the locknut, then slide the valve off the pipe, leaving the old ferrule and nut on the pipe. You then remove the locknut and ferrule from the new valve, slide it on the pipe and tighten it in place with the old nut. The old ferrule remains in its original place and you should have no problems with leaks.

[SSN596]

This is just one of the many nomenclature difficulties that make plumbing confusing.

There are two "groups" of copper tubing in common usage. The 'K,L,M' group is used for most water system piping. It is available in "hard" ( the rigid 10' and 20' sections) and "soft" ( the long coils). In all of the above, they are sold and referred to by their NOMINAL size, meaning the APPROXIMATE INSIDE diameter. The ACTUAL OUTSIDE diameter is always EXACTLY 1/8" larger than the nominal size. Since wall thickness has to vary depending on K,L,M the EXACT inside diameter varies, and this is one reason why fittings are always for the oustide of the tube.

Now, "refrigeration" type tubing is called out by its exact OUTSIDE diameter.

Since all compression fittings use ferrules which must fit an exact OD, compression fittings are most correctly referred to by the OD. But to avoid confusion ( or maybe create it!) they may also be referred to by the NOMINAL copper tube size which they fit.

Bottom line: 1/2 nominal = 5/8 OD compression