What's up with sloppy fitting pipe insulation?

[Rossn]

I have some 1" copper I'm looking to insulate, and surprised how much slop there is between the pipe and insulation... more than 1/8" gap when pressed to one side. I checked some of the rubber foams versions of insulation, as well as some 1-1/4" insulation I got from the supply house, and all seem to have a pretty big gap.

What gives? Is there a solution other than trimming the insulation?

I can get 3/4" on 1" copper, but it's a stretch (literally).

 

[Breplum]

For copper, if you are buying 1-1/8", I.D. (just checked mine for reference), I see about 1/8" heavy but when the product is fully sealed, it is more or less, entrapped air, so not a concern.

 

[Sponsor]

 

[Rossn]

For copper, if you are buying 1-1/8", I.D. (just checked mine for reference), I see about 1/8" heavy but when the product is fully sealed, it is more or less, entrapped air, so not a concern.

Thanks, Breplum. I usually dislike having the gap, as any leak, and air is now flowing. But I guess it is what it is, and see your point.

 

[wwhitney]

Pipe OD:

3/4" CTS = 0.875"
3/4" IPS = 1.05"
1" CTS = 1.125"
1" IPS = 1.315

So if you got pipe insulation for 1" IPS instead of 1" CTS, that would explain your gap. I think often the same insulation is used for 3/4" IPS as 1" CTS, as the ODs aren't too far apart.

Cheers, Wayne

 

[Rossn]

Pipe OD:

3/4" CTS = 0.875"
3/4" IPS = 1.05"
1" CTS = 1.125"
1" IPS = 1.315

So if you got pipe insulation for 1" IPS instead of 1" CTS, that would explain your gap. I think often the same insulation is used for 3/4" IPS as 1" CTS, as the ODs aren't too far apart.

Cheers, Wayne

Thanks - I've check into this more, and it seems the standard is to have loose fitting insulation. I went to the local supply house, who has the Armacell insulation labeled as 7/8", 1-1/8", etc. But... when I put a piece of 3/4" copper into the insulation it rattles around, as the insulation ID is actually just slightly more than 1"

I did talk to Armacell, and they said they usually recommend the loose fit. They also said in my instance I could stretch the 3/4" and tape it with their tape. Now that I've played with stretching a piece of 7/8" insulation over 1" Copper pipe and sealing it, I can hear a squeak when the copper slides through it, so this may be why they over-size it... or possibly for fittings.

Given I'm insulating between joists, versus continuous, tight fit would be ideal, but it would be horrible to have it squeaking. I will test for noise on the pex lines for the radiant, as those would be the ones with greatest thermal expansion.

 

[Fitter30]

Insulation is for iron pipe close to 1 5/16"