Water pressure
Water pressure provided for residences in North America
can be anywhere from 20 PSI to 80 PSI. A typical range is
50 PSI to 60 PSI. Devices that are not limited to 2.5 gallons
per minute (9.5 liters per minute) will use water depending
on the water pressure available. Water pressure measuring
devices are available at most plumbing supply outlets.
Pipe size and water pressure
Pipe size and water pressure determine the amount of water
you will have available for your shower system. Pipe size
can be diminished by older pipes (especially galvinized pipes
rather than copper) that have accumulated depisits on the
inside that impede flow. In an existing home and especially
in an older one, you may want to check if pipes are free from
deposits that impede flow.
Most pipes in residences are called 1/2-inch pipe, even
though they are larger than 1/2-inch in diameter. One-half-inch
pipes generally provide adequate flow for the average shower
system. Using a 3/4-inch shower mixing valve will give you
improved flow, even when connected to 1/2-inch pipes.
For larger systems, however, you may want to consider 3/4-inch
supply pipes. Some systems (a his-and-hers system in one shower
stall for instance) work best using two 3/4-inch shower valves.
In such a case, you would not just branch off a single 3/4-inch
pipe at the shower stall. Instead, run a second line back
to as close as the main water supply source as possible, or
replace a 3/4-inch supply line with a 1-inch line. Another
option is to upgrade your water main (the main valve from
the street) to a larger size and run a larger supply line
from the new water main.
Larger pipe is critically important to water pressure.
Here's why:
Water pressure is greatly reduced over long runs of pipe.
Every foot of pipe restricts water flow by a ratio
of 2:1 (approximately), so keep pipe lengths to a minimum,
but you don't need to be too strict.
On the other hand, every inch of pipe radius increases
water flow by a power of 4 (approximately). That means that
a larger diameter pipe over the same run will deliver substantially
more water than a smaller diameter pipe. The diameter of copper
pipe used in shower systems measures 0.545 for 1/2-inch and
0.785 for 3/4-inch, which is a radius of about 1.44 times
larger. This leads to 4.3 times the water flow through a 3/4-inch
copper pipe over a 1/2-inch copper pipe! The essential rule
here is: the larger the pipe over a longer distance, the
more water flow.
Pressure Boosters
For houses that are supplied by a well, or houses that are
on higher elevations than the rest of the town, a pressure
booster in a system with good pipe conditions will help increase
overall shower pressure. Keidel offers a great overview of
pressure boosters: http://www.keidel.com/mech/boosters.htm.
Hot water supply
Here again, it is important to have a water heater large
enough for everyone in the household to take their shower
and not run out of hot water. To be safe, a 100-gallon water
(or equivalent) heater should be provided for the average
family unit. On-demand heaters are also available. Currently,
they are more expensive than water heaters, but they are more
efficient. You may need two or more systems in order to run
a custom shower system or to fill a custom tub. Check with
your local plumbing supplier.
Back-flow prevention
 It
is theoretically possible for contaminated water to be back-siphoned
into drinking water. For instance, water could be contaminated
if a handheld shower were left in tub water, with the shower
valve open, and at the same time, a breakdown in the water
supply occurred. Most plumbing codes in North America are
therefore asking for installation of a back-flow prevention
device, typically an atmospheric vacuum breaker. When specified,
it is installed between the supply outlet and the flexible
hose leading to the handshower. |
