fiberglass insulation sizing

JustVenting

hi all,

stumbled on this site while planning a fiberglass insulation for our exposed boiler pipes in the basement (for better or worse, the asbestos wrap was removed prior to moving in this summer).


i have a question regarding fiberglass insulation: the majority of our iron pipe seems to be between two insulation sizes that my local plumbing supply store stocks. Attached are pictures of the two sizes(2-1/8 and 2-1/2) on the pipes. My question is which is preferred: the tighter fitting insulation with a gap or the loose fitting insulation?

thanks in advance

JUGHNE

Iron pipe sizes are larger outside diameter than copper pipe sizes.
It depends upon what you ask for.

Your 2 1/2" pipe is most likely 2" iron pipe which is 2 3/8" OD.
The 2 1/8" pipe is most likely 1 1/2" iron pipe which is 1 7/8 OD.

You may have a layer of paint on your pipe.

At the supply store ask to see a 2" iron pipe nipple to compare to how the insulation is fitting. It comes out to be just right and tight.

Often the size is printed along the overlap strip, you want IPS sizing.

Jamie Hall

But in a direct answer -- the tighter fit is better.

JustVenting

thank you for clarifying, Jamie. 

Looks like the 2-1/8 in insulation was indeed for 2” copper pipes. The 2-1/2 in insulation is for 2-1/2” iron pipe. I need 2 in insulation for 2” iron pipe. A little confusing at first, but I got it. Back to the store…

dopey27177

Jughne gave you the answer if you have black pipe 21/2 inch is the proper size.

Jake

JustVenting

i have 2-1/2 inch pipe that leads in into 2 inch pipe. most of the risers come off the 2 inch pipe section. 

delcrossv

Here's the whole sizing chart:

buyinsulationproducts.com/Fiberglass_Pipe_Insulation_Easy_Order_Guide.html