Distributing
Water Around the House
Keeping up with the flow of things in and around your home's water system.
Getting water when you want it, where
you want it is a real balancing act. Pressurized water entering your house
at the water main carries the energy to make it all work. Water is carried
from the main to the various plumbed appliances in the house through pipes.
The entire system must be designed to maintain good water pressure while
reducing the initial pressure to safe, usable levels. Otherwise, you would
blow out your kitchen faucet or showerhead. So, the system is designed
to conserve the pressure while reducing it to a level that can be safely
handled by each household appliance along the way.
Pressure is Everything
A good plumbing system starts with good water pressure. The water that
enters your home from the water main must have enough pressurized energy
to provide a steady flow to all the sinks, toilets, and other plumbed
appliances in the house. This pressure is measured by the amount of force
it exerts per square inch of internal pipe space, or pounds per square
inch (psi). That is a term you will hear and use when debating what size
showerhead you can have or the size of pipe required to support the dishwasher.
When a faucet is turned on or a toilet
is flushed, water in the supply pipes flows toward it. Pressure gets used
up as it moves through the pipes from the main. However, that energy translates
into water velocity, which is measured in gallons per minute. You need
pressure to get velocity, and without velocity there would be no flow.
Ultimately, it's an energy transfer.
Individual plumbing components are designed
to operate within limited ranges of pressure and flow. They cannot handle
the full force of the pressure coming from the water main. A kitchen faucet
designed to provide a maximum flow of six gallons per minute cannot be
safely connected to a supply pipe that delivers one hundred gallons per
minute from the main. So, by design the pressure coming in from the main
is gradually reduced through successively smaller diameter pipes in an
effort to supply quantity and pressure to all fixtures.
Keeping it Flowing
In addition to bringing each appliance the right amount of pressure, the
supply system must also allow several fixtures and appliances to function
at the same time. That is why system design is so important to water pressure
and flow. If there were only one supply main in the house, each open appliance
would reduce pressure and increase velocity until all you had was a trickling
shower at the end of the line. But operating the dishwasher shouldn't
mean that no one can take a shower or that none of the toilets can be
flushed. To solve this problem, supply systems are designed with two or
more feeder pipes that branch off from the main and distribute water to
different areas of the house. Having several feeder pipes rather than
one continuous supply pipe running through the entire house eases the
fluctuations in pressure that occur when an appliance is used.
A Well-Designed System
A plumbing contractor anticipates the likely demands on the water supply
system at various times of day, adds in gravity, and plans the supply
network accordingly. The trick is to balance the need for large pipes
and pressure, with the need to reduce pressure and travel to distant appliances.
The end result should be a well-designed system with good, steady flow
at peak usage times.
Before planning a major renovation that
includes plumbed fixtures, take a hard look at the current water pressure
throughout the house. Then determine whether there is enough pressure
to accommodate another plumbing appliance. Poor pressure doesn't necessarily
mean that you can't add on. Your system may not be taking full advantage
of the water pressure entering the home at the water main. Replacing some
of the pipes in the water supply network could boost your pressure, but
it might also add considerably to the overall cost of the renovation.
Again, balance your desires with the possibilities and your overall budget.
A good plumbing design should help you bring them all together.
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Quick
Tips |
Regulating
water pressure
Decreasing a pipe's diameter reduces the pressure inside the pipe.
In a typical system, the main water pipe entering the home at
the water meter might have a diameter of one to two inches. Feed
pipes branching off the main might be one-half and to inch in
diameter, and the pipes running to individual fixtures might be
one-half inch or less.
Pressure
is further reduced when water has to work against gravity to reach
a second or third floor fixture. It takes approximately 4.5 psi
for a one-inch diameter pipe to push a column of water ten feet
in the air, the standard distance between the floors of a house.
If the pressure of the water entering the house in the basement
from the main line is 50 psi, this pressure is automatically reduced
by about ten percent as it reaches the top floor of a two-story
home--and that's without any other pressure-reducing factors such
as faucets coming into play
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