So I'd like to install some pipe insulation on my heating and domestic
hot water pipes to save energy, and I have some really dumb questions.
First, how big is a 3/4" pipe? I assumed the heating hot water pipe
leaving the boiler was 3/4" and the return was 1/2", but then I tried
measuring them. I measured the circumferences with a piece of string
and then divided them by pi, and came up with about .9" and .6"
respectively. Is the exterior diameter of 3/4" pipe actually some
other size, like how a treated 2x4 piece of wood is actually smaller
than 2" by 4"? What diameters are common in the U.S.? The insulation
for 3/4" pipes seems to have an interior opening of about 1" -- is
there extra room for irregularities?
I heard from a plumber that black foam pipe insulation is useless and
doesn't even have an R value, and that I should get the paper-wrapped
fiberglass insulation instead. Is this true?
What precautions do I need to take when dealing with fiberglass? Are
rubber gloves enough? What's the best way to cut it?
I can't speak about the value of foam rubber pipe insulation, but as to the
outer diameter of pipe, it really depends on the pipe type. Galvanized pipe
has thick walls and copper pipe has thin walls. But I think galvanized 3/4"
pipe is about an inch in diameter. 1/2" is about 5/8" or 3/4" in diameter.
Doesn't really matter that much except for when drilling holes. Even 3/4"
PEX tubing is about an 1" in diameter.
As to working with fiberglass, wear a mask, eye protection, and leather or
rubber gloves and long sleeves. That stuff is terrible to work with and if
you don't wear a mask you'll be hacking it up for hours.
Before you do, think about the situation. Where do the pipes run? Are they
in a place that you do not want to heat? If so, insulation may help. Are
the pipes in the basement where you want at least a little bit of heat?
Then leave the insulation off.
In most basement piping setups, heat that is "lost" from the pipes goes
into the rest of the house that you are going to heat anyway, so there is no
loss, no energy savings to be had. If they are in a crawl space that you
don't want to heat, there will be savings.
What do you think you'll save? The pipes coming out of the boiler - if
they're not insulated, what's the difference? The heat they radiate is
keeping some part of the house warm. Waste of time & effort here.
Now, the hot water heater, I can see a need there. But I wouldn't bother
with insulating the pipes, I'd build a heat trap. They're far more
effective. I don't care for the screw-in heat traps you can buy at the
local plumbing shop, I think they'll fail after a few years so I built one
out of copper pipe. It is nothing more than a loop. Simple physics says
this will work always and with no moving parts, it won't break, rattle or do
anything other than work properly. I only made one, for the hot side. But
if you're after saving the extra 1% of heat, put one on the cold side as
well. It wasn't real easy to do on mine and not really necessary anyhow.
Here is a chart for pipe sizes.
Yes, it is like the 2x4 s except instead of smaller, they are bigger. The
actual size also depends on the thickness of the pipe usually referred to as
schedule or SCH in the chart. That is usually a number and sch 40 is
probably what you have in the house . It could be 80 as that is the two
I measured the circumferences with a piece of string
(Amazon.com product link shortened)83814248&sr=1-61
Its better to use one of this to measure inside and outside diameters.
I have an ok one in the shop and a cheap one from the dollar store in the
glove compartment of my truck.
1/2" copper 5/8" OD , 3/4" 7/8" OD ( outside diameter) Then you have to
decide how thick of insulation you want I would suggest 1". I would wear
some light cloves, dust mask, long sleeves. The insulation is cut with a
knife ( butcher knife) They make a special tape for the insulation joints
the have plastic 90tys that you stuff with insulation. It's really pretty
simple to do, you might have to notch around pipe hangers, joist.
But http://techcalcs.com/technical/pipetable.php says that 1/2" pipe
has an outer diameter of 0.840", and 3/4" pipe is 1.050". Who is
right? And which size pipes are the ones I have which measure .6"
On Jul 7, 11:46 am, firstname.lastname@example.org wrote:
1/2" copper 5/8" OD , 3/4" 7/8" OD ( outside diameter)
But http://techcalcs.com/technical/pipetable.phpsays that 1/2" pipe
has an outer diameter of 0.840", and 3/4" pipe is 1.050".
Who is right?
Short answer........ both are correct
Dave's answer is for copper "tube" which is what I think you have
steel, brass, stainless, PVC "pipe" has the dimensions given in
Here's my best answer based on the info........you do not have "pipe"
you have copper "tube" 1/2 (5/8 od) & 3/4 (7/8 od)
also short answer on the foam...
its fine & foam (5/8" wall thickness) will give you about R4 which is
plenty unless you're running a constant loop through unheated space or
air conditoned space
I tried to post this last night but it wouldn't go.
it's LONG but correct & thorough
When you describe "pipe" or in your case "tube" ,,,,,,,,,, you have
to give the material it is made from as well
When I first saw your the results of you od measurement / calc.....
I thought "man those numbers are really off!"
but taking another look they might be ok
galv steel pipe
nominal 3/4" 1.049" od
nominal 1/2" .840"od
what I think you've got is copper tube
nominal 3/4" ,875" od
nominal 1/2" ,625" od
these numbers correlate well with your string measurements
check out the info in the McMaster catalog www.mcmaster.com
when you dig all the way down to the single item level....they'll give
you a tech drawing with real dimension on it.
domestic water plumbing done in copper is done with copper
tubing.....it is incorrect & confusing to call it "pipe"
Now as for insulation,,,,,,since the od's for 3/4" pipe & 3/4" tube
are fairly close the foam stuff is made to fit both.
I'm not sure if the insulation for 1/2" is different for tube or pipe.
Whether it's worth the effort & cost is matter of the particular
for example if the hot water runs through a basement & you have to
heat the basement, then the heat "lost" to the basement is not really
lost....it's heating the basement
BUT if the water is run through an unheated crawlspace OR through an
air conditioned basement then the heat is actually lost or is fighting
Also if you've got long runs to bathrooms or kitchen having the hot
water cool off on it's way can be annoying
As to the comment of the plumber that black foam is useless, I would
say wrap your hand around an uninsulated running hot water pipe &
compare that to a running insulated hot water pipe. I'll take the
foam insulation over bare copper.
His comment that the foam doesn't have an R value is nonsense......
5/8" foam is about R4
coffee in a copper mug will cool off a lot faster than a copper mug
with a 5/8" foam sleeve
again whether or not its worth the effort depends on the situation
On Fri, 06 Jul 2007 20:09:44 -0700, email@example.com
Do you live alone. I insulated in my basement my hot water for sinks,
showers, and the bathtub, but it's cold anyhow by the time I need hot
I don't know how many people it would take before this wasn't true.
Insulation on hot water pipes is only useful for........
1. reducing temperature drop as the water is delivered
2. reducing ongoing heat loss in a "instant" hot water loop.
Pipe insulation will keep standing water in the pipes hot between
uses only if you're taking about consecutive showers ie hot water
demand every 5 to 10 minutes.
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