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- Downpours beaten
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- Reality check
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- Health check
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- UK farming misery
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- 'Super' solution
- Luxury goes green
- O2 overcomes, too
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- Heat Pumps: The new era
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- Much more to good design
- New lead policy
- India's modern sanitation
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- Contemplating the future
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Structured plumbing offers real benefits.
If the basic structure of the plumbing
system in a home is not efficient, then the efficiency of appliances connected to it is
not going to be maximized.
Ideally, plumbing systems should be designed
instead of merely ‘roughed in’. Moving towards
more centralized system design offers a better
chance of achieving optimum efficiency.
But the question then arises as to how this
rather ‘revolutionary’ approach can be effectively
conveyed to stakeholders including plumbing
suppliers, hydraulic designers, contractors and
regulators.
The entrenched culture of the plumbing
market would need to change, and greater
collaboration would have to occur between
various market sectors such as fixtures, piping,
water heaters, pumps and valves.
In an earlier life Gary Klein ran a plumbing
and electrical contracting business in Lesotho
(southern Africa), and more recently he
has worked as an energy specialist with the California Energy Commission.
Klein is now president of the California-based
consultancy Affiliated International Management.
He says one key to conserving water and energy
is to minimize the time it takes to deliver hot
water, and this can be achieved by the design of
what he calls structured plumbing systems.
Klein believes the best way to achieve an
efficient structured plumbing system is to build
back-to-back and stacked bathrooms and
kitchens so that a plumbing core can
be created.
“Water heating is a big user of residential
energy, at 15-30% of a dwelling’s total energy
consumption. About 20% of stationary energy in
the United States goes to water in some form. “At the outset, questions need to be asked
and conventional ways of thinking challenged.
For example, have you measured the hot water
demand in the facilities you are designing for?
The aim should be to give people what they
want (hot water) and what they expect (safety,
reliability and convenience) as efficiently as
possible.
“However, there are several potentially
conflicting trends that have to be taken into
account. Larger houses are being built while
city water pressures are reducing, and more
plumbing fittings are being installed but with
lower flow rates.
“The result is a longer wait for hot water, less
pressure, lower performance, customers who are
less satisfied and increased complaints.”
The elements in a building that can affect
the efficiency of a hot water system include the
water heater, piping, fixtures, fittings, appliances
and behavior. Interactions between them can
have a direct effect on the system performance.
“There should be a focus on reducing
structural and behavioral waste by increasing
the efficiency of the system and improving the
use of water.
“System designers should begin with the
desired end in mind by careful consideration
of appropriate flow rates for fixtures and
appliances, pipe sizing, water heater sizing and
energy supply sizing.
“For residential water pressure up to 50psi
the maximum allowable velocity dictates pipe
sizing, and for pressure below 35psi friction loss
in the pipe dominates pipe sizing.
“Consideration of flow rate is important
because the need to accommodate a high flow
rate leads to a larger pipe size, which in turn
means greater volume in the pipe and increased
energy waste during the use and cool down
phases of a hot water event.
“If the pipes are sized for increased flow,
and a lower flow rate fixture is used, this can
also result in energy waste during the delivery
phase.”
Klein says the ideal hot water distribution
system has the smallest volume of pipe
(combination of length and smallest practical
diameter) from the source of hot water to
the fixture. The source is the water heater, or
sometimes the trunk line.
“For a given layout or floor plan of hot water
outlet locations, the ideal system will have the
shortest buildable trunk line, few or no branches,
the shortest buildable twigs, the fewest
plumbing restrictions, and insulation on all hot
water pipes.
“Insulation will reduce heat loss, which is
particularly important for low-flow fixtures and
appliances, and it will also increase the time
pipes stay hot between events.
“A few years ago my colleagues and I gave
ourselves a challenge. How would you deliver
hot water to every fixture and appliance, wasting
no more energy than we currently waste and
wasting no more than one cupful waiting for the
hot water to arrive?
“We found five solutions, one of which –
structured plumbing – is the most practical. We
also learned in the process that wasting no more
than one cupful while waiting at all fixtures is a
tough goal to meet. Two cups is more practical.
“In other words, the aim is to improve the
delivery phase to provide hotter water sooner by
minimizing the waste of water, energy and time.”
When looking to improve the cool-down phase
between hot water events, several factors should
be considered. They include where the event is
in relation to the source of hot water, time until
the next event, temperature of the hot water
needed for that subsequent event, and volume
of water in the pipe that eventually cools down.
Pipe insulation is essential for improving the
use and cool-down phases of a hot water event.
A typical structured plumbing system includes
a circulation loop close to the fixtures and
appliances. This can be a fully heated or halfheated
loop, with a dedicated (three-pipe) or a
cold water (two-pipe) return line, depending on
the floor plan.
“The system would also include small-volume
twig lines no larger than half-inch (13mm)
diameter, although a larger diameter would be
needed for fittings and appliances with a high
flow rate,” Klein says.
“The twig lines should be no more than 10
plumbing feet (3m) long, or two cups in volume,
but some exceptions could include garden tubs,
washing machines, and sinks or appliances on
an island on a concrete slab.
“A demand-controlled pumping system would
also be installed with wired or wireless buttons
or motion sensors. The pump would be activated
to pre-heat the insulated line, and it would shut
off automatically, usually in much less than a
minute.
“Minimum R-4 insulation on all hot water
pipes should ensure that water in the pipes
stays hot 30-40 minutes after the last hot water
event.”
Such a system will minimize the waste of
water, energy and time, and will provide the
most flexible and cost-effective solution for
today’s floor plans, resulting in high customer
satisfaction.
People generally want convenience, but some
crucial questions should be asked. How many
water heaters are needed in a home?
“Most people think they use hot water several
hours a day when the reality is under one hour.
Customers can have the floor plan they want,
and the plumbing system can be designed as
efficiently as possible given that layout.” Klein
says several changes are proposed for the
2009 version of the Uniform Plumbing Code,
and in California and North Carolina, seeking to
improve the performance of domestic hot water
distribution systems in all buildings.
Changes being considered to the code
include defining piping suitable for hot water
distribution, enabling use of smaller-diameter
piping for fixtures with lower flow rates, requiring insulation of all hot water distribution piping and
requiring buried potable distribution piping to be
installed in a conduit.
There are also incentive programs sponsored
by water and energy utilities that provide a
financial incentive for installation of structured
plumbing. In addition, the California Energy
Commission, which provides building and
appliance Standards, is developing clearer
guidelines on how to structure efficient
plumbing.
Klein believes greater uptake of structured
plumbing systems would be achieved through
incentives rather than mandatory requirements.
“Incentive points are preferable to legislation,
at least initially, and once the benefits become
more widely recognized the uptake should
escalate. Increases in the cost of energy and
water will also help. The cost of energy per
annum in the average home in the US is about
$300, and $100 for water – which is too low
and does not encourage efficient use of these
resources.
“The cost/benefit of structured plumbing
can vary substantially from project to project.
Actions such as changing the location of trunk
lines, rerouting the plumbing and keeping
the twigs as small as possible can result in
substantial cost savings – in some instances
customers can recoup pumping costs in a few
months.
“Projects I have been involved with have
resulted in the footage of pipe being cut by up
to a factor of five. Consumers are better off in all
cases when water/sewer and energy costs are
taken into account.”
Klein says payback of costs can generally be
achieved within five years and in some cases
within six months, particularly where the system
is installed in a new construction. The benefit
stream can be built into the mortgage, and the
savings can be more than the marginal cost of
the mortgage.
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