Plumbing – back to the start

by Paul Angus
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While HVAC is always a prime target in looking at energy and water savings, don’t overlook the plumbing system, writes PAUL ANGUS.

With energy and water costs constantly increasing, facility management resources are becoming progressively limited. Smarter buildings effectively require smarter thinking to reduce costs, so managers have begun looking for methods to improve the performance of their facilities’ energy and water consuming systems.

A strong emphasis is always on heating ventilation and air-conditioning (HVAC) systems, but could you be overlooking and underestimating the plumbing system within your building? It could offer substantial energy and water savings.


At first glance, your facility could tick all the boxes by looking appealing, providing plenty of natural daylight, incorporating the latest in control technologies, plus offering the bonus of no thermal comfort complaints.

But, below the surface, your building systems may be wasting energy and water – effectively flushing money down the drain – with few noticeable symptoms. If it’s not broken, it doesn’t need fixing. But when you do have to replace or repair plant, pipework and ancillary valves that have failed, you can open a can of worms if you don’t fully understand the building services installed within your facility.

Undertaking numerous due diligence surveys on a variety of existing facilities for pre-acquisition reports has shown that there is always an issue, namely, the lack of operation and maintenance manuals being made available. How a building can operate without this essential information or even an asset register listing the manufacturer, model number, capacity and installation date is puzzling, and must waste so much time.

When key plant goes offline, being able to reference the operation and maintenance manual allows the manager to quickly refer to key parts enabling fast replacement. Not having access to this essential information can, however, have significant repercussions.

Most importantly, how can you, the facility manager, be confident that the system has been fully commissioned, plan for preventative maintenance and implement to fine-tune the plant? Retro-commissioning provides a process that offers managers an organised approach to identifying operating problems with existing facilities and systems, and opportunities for increased energy and water efficiency, while also reducing overall operating costs.

When a building has been operating for a number of years, retro-commissioning allows the facility to effectively fine-tune the system performance and efficiency within the building to the original design intent. But how can this occur, if the original design intent is not available?

Operation and maintenance manuals should be available and are key documents to record the commissioning process, identify where the plant is located, highlight the key ongoing maintenance requirements and provide ‘As Built’ drawings to assist in locating the plant within the facility.


The facility may have achieved a fantastic ratings from Green Star/LEED (Leadership in Energy and Environmental Design) and NABERS (National Australian Built Environment Rating System). But let’s say your building loses its NABERS rating. That can have major ramifications, in terms of commercial and reputational consequences, plus take over 12 months to recover, if not more.

Still confused about the difference between a Green Star rating for buildings and a NABERS rating? In summary, Green Star rates the design intent of a how a facility will operate, whereas NABERS rates the actual performance of the building, so the numbers of stars achieved can be variable.

Within high-performance buildings, the latest technology is worthless if it is not connected to the facility building management system (BMS), as you can’t measure what you are not monitoring. I’ve lost count of the number of occasions I’ve seen water and gas meters/ sub-meters not connected to the BMS.

Measurement is the key to improvement. Facilities managers have to be responsive to ensure that energy and water performance is continually monitored to review and compare any loss of efficiency and the need for retro-commissioning.


Retro-commissioning, much like commissioning for new buildings, is an organised process that identifies facility performance objectives, enabling a methodology for testing and verifying those objectives are achieved, and documentation of the process. However, retro-commissioning is performed on facilities that are already in operation and it is typically in response to problems that exist, otherwise termed as ‘reactive maintenance’.

So how does this reflect on your plumbing system and does it still apply? The plumbing is directly responsible for a significant amount of energy and water usage and should never be overlooked or underestimated.

The economics of plumbing systems include both capital (CAPEX) and operating (OPEX) costs. The latter cost-effectively comprises energy and water consumption, maintenance and repair, retro-commissioning, future plant replacement and asset preservation.

Within a plumbing system, most facility managers understand hot water, cold water, gas, stormwater and sewage pumping systems, in terms of operational performance, and that these systems cost significant funds to operate. A proportion of building owners also understand that plumbing systems have a greater impact on the building asset value by regulating public health, wholesome drinking water, hot water and sanitation.

But fewer understand how much the plumbing systems impact their bottom line. It is the role of the engineering team and the Independent Commissioning Agent (ICA) to educate an owner’s team on the economic impacts of plumbing systems.


So, what falls under the two distinctive areas of CAPEX and OPEX? OPEX is an ongoing cost for running the facility, while CAPEX is the cost of developing or providing non-consumable parts for the ongoing maintenance and replacement of plant.

Building owners have varying expectations regarding the overall economic impact of plumbing systems. It is safe to say all building owners care about CAPEX; however, not all owners understand the impact of CAPEX on the OPEX. There is effectively a fine line between the two for each facility. Building owners often have a budget threshold for spending CAPEX, in order to gain OPEX.

Any life cycle analysis may be driven by the type of building that, in the majority of facilities, has an operational life span of approximately 25 years. However, within this period, most plumbing systems will require replacement, an upgrade or major/ minor repairs. The Chartered Institution of Building Services Engineers (CIBSE) publishes life expectancies of major plant equipment. Omitting the replacement cost of the plumbing system in the life cycle cost (LCC) does not represent the true costs of owning the plumbing system. The facility manager should include the replacement costs in the year of expected system failure.

Accounting for water usage is very similar to energy modelling. The annual consumption is determined and the inflation and discount rate applied to this, as well as costs over the life cycle study period. Once again, omitting these costs does not represent the true costs of the plumbing system. Water and sewer infrastructure costs also should be factored in the LCC.


Preventative maintenance and fine-tuning is based primarily on the commissioning process recommended in CIBSE’s Guide M & W: Building Commissioning Maintenance Engineering and Management and Knowledge Series KS21: Competency

and competency management systems in facilities management. Commissioning and ongoing preventative maintenance protocols should follow the process, which has been adopted by Green Star and leading industry organisations. It does not focus upon specific systems or assemblies, but rather presents a design philosophy that can be followed to commission any building, within any sector. Often, the initial plumbing equipment plant sizes are adjusted to satisfy the engineering people, calculating the various plumbing systems, including hot/cold water peak demand, gas supply total load, sewer discharge and stormwater services.

At this point, engineers will consider any diversity in operating the systems to represent real-time occupancy and any relevant operating frequency. Once again, the plumbing plant equipment and reticulation systems’ capacities can be adjusted. At the end of
the design-development phase, updated equipment selections are made and finalised.


So what does this have to do with the economics of the plumbing systems? Effectively, when the construction program is delayed or altered to omit the refinement to commission the plumbing system, the system capacities may end up significantly oversized. This is due to being initially selected on rule of thumb calculations and never fine-tuned to reflect the developed load calculations and diversity of operation.

The impact on the CAPEX budget can be significant. The impact on OPEX will be problematic, due to the operating limitations of the plumbing equipment. Underperformance of the plumbing system can create early equipment failure, including oversized pumps creating high velocities – effectively eroding/corroding pipework, hot water pipework cavitation due to the system not being balanced, inefficient operation (increasing operating expenses) and occupant dissatisfaction. Furthermore, the ongoing NABERS assessment will identify any key energy and water consumption, which will adversely affect the building’s rating, and ultimately identify where key energy and water costs are being spent.

Paul Angus is an associate director – Hydraulic Services at AECOM, based in Sydney, with strong commercial and technical capability in developing and delivering hydraulic design strategies and solutions.

This article also appears in the June/July issue of Facility Management magazine.

Image: 123RF’s Oleg Zhukov ©

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