Gary Slusser wrote:

"George E. Cawthon" wrote
I believe that the 1/2" copper is a direct replacement for 3/4" iron
pipe. 1/2" iron pipe is totally inadequate for any modern house. If
it were my house I would replace the larger runs with 1" or 3/4"
copper and the branch runs with 3/4" or 1/2" copper. Follow what
others said about the type of copper pipe

Paul J wrote:

I am ready and about to buy materials for the repiping from galvanized
1/2" to copper ?", but what size to use? I would like to go with 1/2"
type K but that takes up more inside diameter then M and L. Should I
go with 5/8" K, 3/4" K or just not be worried about the inside
diameter because it is a very small difference? Then again the
galvanized pipe probably has only an 1/8" openning anyway from all the
years of crap in it.

Actually, 1/2" and 3/4" copper or galvanized has the same OD although the ID
of L and M copper will be only slightly larger than galvanized and roughly
about the same a K copper.

But.... with water conservation fixtures, what's the need to go to so much
larger tubing until we figure the peak demand that's needed for the system?
You do that by adding up the max gpm of each fixture or use the fixture
count method. And in new construction and many repipe jobs, homeruns, like
running Romex, using PEX is being used with excellent results. No fittings
except one on each end of the run and each run is valved at a central
manifold.

Gary
Quality Water Associates
www.qualitywaterassociates.com
Bulletin Board www.qualitywaterassociates.com/phpBB2/

It isn't the size it is the smoothness of the pipe wall that makes a
difference in flow. Sizing pipe based on the flow needed is driven by
economics. As a homeowner, especially a do it yourself homeowner,
economics is only one factor and may not be the most important factor
for me. I would use a larger size of pipe to reduce flow noise, a
larger slower fan and larger ducts to reduce air noise, a larger size
wire to reduce voltage drop, heavier floor joists and subflooring for
greater solidity, thicker outside walls for comfort and sound control,
etc. If I eliminate the labor cost, and since labor is a major cost
in any construction, I can devote more capital toward premium
construction elements.