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.