I have the old 1 inch copper pipes in the basement. I'm about to reduce the size of the pipe into 3/4. So I bought a reducer, SharkBite 1/2 x 3/4 reducer(picture 1). The problem is my pipe size is a little less than 1 inch(picture 2). The outer diameter is 15/16 while 1-inch-copper-pipe at Home Depot is exactly 1 inch(picture 3). I measured my pipe multiple times from the different angles but still it's 15/16. I measured the inner diameter of the SharkBite reducer and it was exactly 1 inch.

Do you think I could still use the SharkBite reducer even the pipe is not exactly 1 inch? I have to know this before cutting the pipe. I need to install a valve right after cutting the pipe without any problem to use the water in the house. Any advice would be appreciated :)

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  • 2
    Threaded red brass is not copper. Especially from a "pipe size" point of view. Copper pipes are not threaded, so that's red brass pipe because it has threads.
    – Ecnerwal
    Nov 24, 2021 at 1:38

3 Answers 3


Okay, there is a lot to unpack here.


You are reading your calipers wrong. You should be looking at the ZERO on the slider.

First picture shows 1-1/16". Also, you should not be measuring the threads; measure the solid pipe.

Second picture shows 1-1/8"; this is the correct actual dimensions for nominal 1" copper.


Copper tubing does not get threaded; it's not thick enough and doing so would compromise its integrity. That first picture is not copper, it's red brass; nominal 3/4".

Below is a picture of a male adapter (MIP) being sweated onto a copper tube:

enter image description here

Note: this is not what your current situation is.


That SharkBite is unlikely to succeed. Check the packaging for a list of compatible piping. Usually it's "PEX, copper, CPVC, PE-RT, or HDPE Pipe". If your existing pipe is not one of those then you need a different solution.


Do NOT cut that tubing without a proper plan in place. If you cut it then you'll need to manually thread it with some expensive equipment which I assume you do not possess.

I need to install a valve right after cutting the pipe without any problem to use the water in the house.

This statement scares me. Are you planning to cut the pipe without shutting the water off in hopes of attaching a shut-off valve? I hope you enjoy your new basement pool.

Have fun being this guy: https://www.youtube.com/watch?v=OP30okjpCko

  • 1
    Thanks you for your answers!! I have a better understanding about my pipe and the measuring. I really appreciate your concerns. I'll shut off the main valve before cutting the pipe 😆 I don't want to be a guy in the video lol
    – sol1000
    Nov 24, 2021 at 16:07
  • @sol1000 You're welcome! Realistically this should be about an hour of work for a plumber. You can expect to pay about $150 assuming that the plumber has the tools to re-thread the pipe after cutting it.
    – MonkeyZeus
    Nov 24, 2021 at 16:11
  • Let's give OP benefit of the doubt and say "right after cutting" means with the water turned off, but cannot leave whole house without water for days while this project unfolds.
    – jay613
    Nov 24, 2021 at 16:56
  • @MonkeyZeus if OP cuts off threading, would a 3/4x3/4 brass compression coupling be able to mate to the 3/4 brass on one side and to a short 3/4 copper stub on the other, providing a set-off point for further work?
    – jay613
    Nov 24, 2021 at 16:57
  • 1
    @jay613 Go ahead and find a compression fitting for schedule 40 pipe and I'll let you know my thoughts afterwards. Hint: terrylove.com/forums/index.php?threads/…
    – MonkeyZeus
    Nov 24, 2021 at 17:14

The existing pipe in your photo is threaded pipe, while the photo you took at Home Depot is copper tubing. Copper tubing is manufactured to an outside diameter that is 1/8" larger than the nominal dimension - i.e. 1" tubing is actually 1.125" outside diameter. You'll see that measurement if you look at the zero reference in that photo. Pipe dimensions are also a little odd. For example, a 1" pipe has an outside diameter of 1.315 inches, and an inside diameter that's kind of close to 1 inch, if it's standard thickness (sch. 40).

Since the pipe you need to connect to is threaded, can you unscrew it and install a threaded valve? I'm guessing it's 3/4" pipe, which has an outside diameter of 1.050". You're measuring about 1.0625 which may differ a bit because your measurement is in the threaded portion.

Here is a pipe dimension chart. There are many others available.

And Here is a copper tubing dimension chart.

  • The Peterson chart for tubing is handy ; However they certainly confuse things by listing "nominal pipe size" when they mean tubing. Nov 24, 2021 at 16:46

Copper comes as tubing and as pipe; they have different OD, and wall thickness is different for different "grades" ( K,L,M). Pipe only comes in certain ANSI OD sizes; Wall can vary, such as Sch 40 or 80 or 120. Any pipe of a size ( such as 1 in.) will thread into any other pipe, copper, steel, stainless, etc. Tubing comes in any size a mill and a purchaser agree upon .When I was on the ASTM commitees , they were considered so different that there were two committees, one for pipe and one for tube. They have now been combined. You should be able to figure out what you have from the dimensions of @ Mark.

  • 2
    What do you mean by "There is no such thing as "red brass" pipe/tubing in general use ( US)."? Clearly it's in use in OP's situation. If you need to buy some then check out asc-es.com/products/schedule-40-brass-pipe. Not everything starts and ends at Home Depot.
    – MonkeyZeus
    Nov 24, 2021 at 16:46
  • trentonpipe.com/products/red-brass-pipe and "Copper Tube Size" is very, very standard. ASTM B88 STANDARD SPECIFICATION FOR SEAMLESS COPPER WATER TUBE, specifically.
    – Ecnerwal
    Nov 24, 2021 at 18:37
  • 2
    I am wrong, maybe not too old to learn. ASTM B 88 is copper. But B 43 is 85% copper /15% zinc, certainly a red brass. Also named alloy 230 in the Copper Development Association handbook. As pipe ASTM B-43, as tube ASTM B-111, B-135, B359. As wire , B134, as flatstock , B-36 and B-134. Somehow I never encountered it, my bad. Nov 24, 2021 at 22:38

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