zxcvbob wrote:

George E. Cawthon wrote:

George we are talking a full potable water pipe, and probably cold water at
that, an enclosed water line. And certainly not some open ditch. We also
aren't speaking of the water as it exits the faucet or fixture. where the
noise is caused by the water splashing or the aerator makes noise.


I know what we are talking about. We are talking about the noise of
water running through pipes. I've lived in houses with noisy water
lines. Most noise is caused at valves and then transmitted to the
walls through the pipes. And, the largest noise makers are usually
the valves associated with the water closets. The second noisest in
my experience is the outside faucets. But any constructed point in
the water line is a potential noise maker. And no, we aren't talking
about the noise of water splashing. We are talking about the kind of
noisy you hear when you are 30 or 40 feet from a fixture and separated
by several walls.

[snip]
That's pure BS. There is a MINIUM pipe size based on acceptable flow
rate. Even you admit that, by saying you want to maintain a water
velocity of 6-7 feet per second, because the way you reduce velocity
is by increasing the size of the pipe. There is no MAXIMUM pipe size
unless you want to base it on pure practicality or economics. Most
fixtures have short, small (1/4" or 3/8") pipes between the fixture
and the supply line that determines the flow through the fixture, or
the fixture itself may have smaller openings that determines the
maximum flow or the supply valve may be the flow limiter. It doesn't
make any difference to the flow out of the one fixture if the supply
line is 1/2", 3/4" or 1 inch. Unless, you have several fixtures
flowing which reduces the pressure and then you want the supply line
to be larger.

There is no single size correct for water pipe any more than there is
a specific size for a bed room. If you like a big airy room, then
make the bedroom big. If you like a lot of flow even when other
fixtures are open, then use large diameter pipes. I doesn't make much
sense, unless you have a long run, to use pipe larger than your
metered supply. And yes, here we have an option of 3/4" 1" and 2"
meter supply.


That part about 3/4" iron/galvanized and 1/2" copper... yes, you'll always
get more water through 1/2" copper than a rusted up, full of encrustation
filled galvanized pipe, but not a clean one. With a clean one, you get more
water by about 2-3 times more with the 3/4". Prove me wrong if you can. And
it 'is' more the size of the pipe than the smoothness of the pipe, and
plastics are about the smoothest you can find; hard water scale does not
stick to the inside of plastics, nor do they rust or corrode which causes
roughness.


Hey, I don't know if it is true or not but several books on plumbing
indicate that 1/2" copper will replace 3/4" iron because of the
greater flow rate through copper and they weren't talking about rust
filled iron pipes. I do know that iron pipe, especially when you
consider the elboes and other connectors can be extremely rough
compare to copper.


Those "several books on plumbing" either didn't know what they were talking
about, or they were having you design for 50 years later when the iron
pipes *might* be full of corrosion. For a given size, copper will supply a
little more water because it's smoother inside and you have less
turbulence. But this affect is quickly overwhemed by the larger cross
sectional area of the next size larger iron pipe.

Ok, so the books are wrong.

For cold water supply lines, using a larger pipe than necessary doesn't
hurt anything but it doesn't gain you much either. But for hot water
supply lines, using too large a pipe will waste water and energy.

That was exactly my point, a larger size won't hurt. Larger size hot
water (and cold water) supply lines may waste heat but they also
reduce shower temperature variations when the WC are flushed or
washing machines are operating.

Generally speaking, 1/2" pipe can supply more than enough water for one
faucet but not necessarily enough for two or three (assuming we are talking
about relatively short runs inside a house, not 200' of irrigation pipe.)
Whether you can supply 1, 2, or 3 with a 1/2" pipe depends on the water
pressure and the flow rate of each of those faucets.

Bob, my first comment said 1/2" iron was in adequate and recommended
using a 1" or 3/4" copper pipe.

Best regards,
Bob