Eric in North TX wrote:
btw I had to talk my neighbor out of using 1.25" for his main line

cheers
Bob

Why? 3" would be ok if cost was no object. While it will still only
flow to the limit of the smallest restriction, the volume of water
"stored" in the big pipe would still help.


Well cost is nearly always a factor. Plus my neighbor & I help each
other out on projects & although we tend towards overkill we balance
each other out. & hopefully minimize our desire for "wasted" overkill.

For a 75' x 150' lot & a 1" meter ....a 1" line is right
size.....1.25" is unnecessary as is 3".

IMHO a bigger line won't buy very much (almost none) improvement in
performance.......water is not very compressible & the concept of water
"stored" requires some sort of accumulator (LARGE flexible lines, or a
piston or bladder style accumulator) just adding large metal lin won't
do much.

Incompressibles (water, hydraulic fluid, etc) need to be delivered on a
real time basis;

instantaneous supply must equal instantaneous

or a system accumulator must be present. to supply instantaneous peak
(short term) demands & buffer instantaneous peak supply (the cause of
water hammer)

So a large line isn't going to "store" much if any extra water but it
will have less head loss that a smaller line.

another mis-conception about water flow / hydraulics is

"....... it will still only flow to the limit of the smallest
restriction......"

that is not entirely true....hydraulic supplies suffer head loss
through the lines, fittings, valves, & other restrictions...the cool
thing about analyzing the system is that the "head loss" (pressure
loss) due to each item can be expressed in equivalent length of
straight pipe

so a valve (depending on style) might add a between 1' & 10' of
"extra" pipe length....an elbow maybe 4'.

Yeah putting a 1" valve in a 3" line is REALLY gonna add some large
loss (a rather unrealistic example) but the system will still preform
better than a completely plumbed 3/4" system

Well......we might get enough losses in the transition from 1" up to 3"
& back to 1" overwhelm the postive effect of the 3" . Plus analyzing
a mixed size system (by hand) gets to be a real PITA.

In any case the way a complete hydraulic system performs is a function
of layout, pipe sizes & fittings...combined with the demand...ie flow
velocities, since head loss is a dependent on flow velocity.

Sorry about the long winded post...I guess I got overcome by Nick's
evil influence.........

cheers
Bob