Re: Plumbing - Pipe size question
- From: BobK207 <rkazanjy@xxxxxxxxx>
- Date: 24 May 2007 09:49:44 -0700
On May 24, 5:36 am, "Sacramento Dave" <diac...@xxxxxxxxxxxxx> wrote:
Larger pipe will give MORE pressure.
Your right I'm wrong But I'm just a plumber Pipe Fitter
I think some of us might be saying the same thing but just talking
passed each other.
The city water pressure & flow available at your water meter is what
you have to work with.
Installing a larger pipe from curb to house (like removing a 1/2 &
putting in a 3/4 OR removing a 3/4 & putting in a 1") won't give
more pressure at the curb BUT you'll have less pressure drop (at flow)
with the larger pipe.
So when some of the guys in the group say that "larger pipe gives more
pressure" they're kinda correct in that the larger pipe has lower
pressure drop SO at the far end of the larger pipe the water is
delivered at a higher pressure than a smaller pipe would deliver.
No way you're gonna get HIGHER pressure than at the meter (unless you
got a booster pump in there somewhere) BUT you will get less pressure
drop with larger pipe.
Bigger pipes give less pressure drop so if you're working with low
city pressure bigger pipes will preserve more of your limited
pressure.
There is one very annoying drawback to larger pipe.......large hot
water lines (with no recirculating pump) make the wait for hot water
longer. A 3/4" hot water line will more than double the wait time
for hot water
If you've got a 10 ft run from water heater to fixture not a problem
if it's 40 ft maybe the wait is too long & you'll want a smaller line
or a pump.
When Dave suggests a pro size your system...it's not a bad idea IF
you're want optimum performance & lower cost.
If you're handy with a calculator & can understand pressure drop
tables...you can do it yourself.
I have the pressure drop tables for PEX here's a link to copper tube
pressure drops
http://www.copper.org/applications/plumbing/techref/cth/tables/cth_table6.htm
It all depends on the water demand, tube size, run lengths & starting
city water pressure.
If you've got a small house or a 2 story with stacked bathrooms &
short run to the kitchen / laundry 1/2 copper is proabably fine. If
you've got a spread out ranch maybe it's a little small.
I just re-did my 2 story (with stacked bathrooms & medium run to the
kitchen / laundry). I ran 1" copper from curb to "water heater /
PEX manifold" split to 3/4" there. PEX manifolds feed every fixture
with 1/2" PEX BUT I've got two showers on old 1/2" copper that I
chose not to replace since it was perfectly good. I also cheated &
put the upstairs toilet on the shower cold water line to make the re-
pipe easier. The toilet can be flushed when the shower is running
with no noticeable effect
According to the copper & PEX pressure drop tables (combined
calculation) ..........
I'm losing about 2 or 3 psi (max) from manifold to shower head (both
showers running) ....with about a 1 or 2 psi change when the second
shower goes on or off. My static water pressure is regulated to
65psi
Long winded post but for the OP.........if your runs are short (less
than 50') without doing the calcs I'd guess that your system is a
little undersized if ALL of the house is done in 1/2"
The suggestion of 3/4" feed to the water heater is a good one but
replacing ALL of your 1/2" with 3/4" is a lot of work & cost for ????
gain.
cheers
Bob
.
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