I am buying insulation for our hot-water pipes, which have an outside diameter of 5/8 of an inch. One website says that this is actually called 1/2-inch pipe, even though that is not the inside diameter. (It also says that the inside diameter varies by application.)
Janet
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Replies
You've got what plumbers call 1/2" copper pipe, but what refrigeration guys call 5/8" tube. Go figure.
Depending on the application, plumbers use Type M, L, or K copper pipe, and each of these has a different wall thickness, but the outside diameter stays the same, otherwise, there would have to be Type M, L, or K fittings, and isn't it already confusing enough?
Yeah, as a general rule (for which I'm sure there are many exceptions), if it's called "pipe" then it's sized by its "nominal" inside diameter, while if it's called "tube" then it's sized by its (generally more precise) outside diameter.
The inside diameter of the pipe is used since that determines how much fluid can flow through the pipe, but the inside diameter varies slightly (not enough to significantly affect flow) based on the "weight" of the pipe, and also it's composition. Modern iron pipe, eg, is hardly ever even close to its "nominal" diameter, since pipe walls have gotten thinner over the years as manufacturing techniques have improved. But the external diameter is maintained since that's what gets threaded and jointed.
I think it's extinct now, but for a time there was a type of brass pipe called "threadless pipe". It was meant to be brazed, and the OD was equal to the the minor diameter, or root, of a threaded portion of the original pipe size.
A few years ago I watched some guys install TIG welded iron pipe through our building, a diesel feed for a generator. The pipe was of course threadless and used threadless fittings that otherwise looked like regular iron pipe fittings. No idea what size it was, specifically -- was somewhere in the 1/2" to 3/4" range, compared to regular iron pipe.
Threaded Pipe
Back in the old days when we were stil using a lot of brass pipe in new installs it all came without threads. Even steel pipe came that way until they came out with whats called T+C (Thread and Coupling), you may still be able to get both without thrreads.
The threadless pipe I mean was never threaded at all--it was brazed into the fittings like soldered copper pipe is done now. The wall thickness was what you'd get on threaded pipe if you measured the thickness from the root of the thread to the I.D.
I'm just guessing, but I think it was done to meet code in certain cities like NYC where all water pipes in buildings were required to be brass pipe, and the threadless pipe was a way to cut costs.
Pipe Sizing
" since pipe walls have gotten thinner over the years as manufacturing techniques have improved"
I think that if the wall size is changed the schedule is changed, I don't think that you can use a schedule 40 on a schedule 80 installation, just a thought.
Insulation
If you are measuring copper pipe that is correct, 1/2in. I.D.= 5/8 O.D., if you tell the supplier where you buy it they should know what you need.
Thank you!
Good thing I'm doing only small projects. One could waste a lot of time using the "wrong" system.
Janet
Thank you!
Good thing I'm doing only small projects. One could waste a lot of time and money using the "wrong" system.
Janet
What is the most common size?
Home Despot had fiberglass insulation in a variety of sizes, but not for 1/2-inch. Is this an outmoded size?
Janet
Commonly foam
The most common form of pipe insulation is a black foam rubber rather than fiberglass; slit along it's length to facilitate installation on existing pipes.
HD carries foam insulation in lengths 4' - 6' long - can't remember lengths. At least the associate told you the truth when you asked for fiberglass insulation for 1/2" copper pipe --- "Nope, we don't carry that." He probably did not know what those funny looking black things were over in aisle 32.
1/2" copper pipe is very alive and well.
Jim
Elastomeric foam
I had been hoping to find something with a higher R value than foam rubber. If not fiberglass, then the stuff used here:
http://www.youtube.com/watch?v=TfKVVG2a5Oo
Any idea where to buy it?
Janet
If you can't find it at HD, you can find it at Lowes.
Ahhh, errr?
What we have here is a failure to communicate.
The title of the video is "How to Install Rubber (elastomeric) Foam Pipe Insulation On Small Copper Pipe, 90's and T's"
I omitted the "elastomeric" descriptor, but this is the "foam rubber" pipe insulation which I was suggesting in my original response.
The pipe shown in the video is 3/4", but the material is also readily available for 1/2".
I buy it at my local HD; if you are not having any luck at HD, try Lowes, or any plumbing or HVAC supply house.
In the unlikely event that you cannot locate 1/2", but can find 3/4" - use the 3/4" - a little extra dead air surrrounding the pipe will not hurt - certainly better than nothing!
Jim
Pipe Insulation
Pipe insulation is usually ordered by the iron size, so to get it for copper you order by the o.d. of the pipe 1/2 in. copper = 5/8 o.d. If you can/t get it at one of the big boxes you can probably get it from an isulation supplier. call around and ask.