Integrating plumbing into the overall design

Having a qualified, knowledgeable plumbing engineer involved in early planning will help select the right system and equipment for the project before construction begins.
By Kari Engen, PE, CxA, LEED AP; WD Partners September 27, 2017

Learning objectives:

  • Learn about the integrative design process.
  • Understand how integrating the plumbing engineer can enhance system design.
  • Review the water efficiencies that can be achieved by integrating the plumbing design early.

Due to the increasing interest in U.S. Green Building Council LEED certification, and sustainable design in general, the use of an integrative design process can add value to a project’s success via increased energy efficiency, aesthetic appeal, and innovative building components and in decreased construction cost,. To incorporate an integrative design process, the project coordinator brings together all designers, stakeholders, the commissioning agent, and other individuals who have an interest in the completion of the project.

Early participation in design decisions creates an inclusive environment that ensures buy-in and a cohesive team approach to the building’s basis of design. At several stages of the design process, an integrated team is often returning to the table to discuss progress, revisit any decisions that are creating obstacles to success, examine any new issues that arise, and collaborate to resolve them in a manner that respects how such decisions affect each discipline and/or stakeholders.

The integrative design process urges the early inclusion of all project team members in the planning stages of any project. Obvious members to invite to the table include the client or owner; the architect; electrical, mechanical, structural and civil engineers; and community officials.

The plumbing engineer’s role

Often overlooked in these early planning stages, the plumbing designer or engineer can provide value to the project due to his or her expertise in water, waste, storm/sewer, fuel-gas, or medical-gas systems. Including the plumbing engineer during the initial planning phase of any project can eliminate costly delays during construction. Engaging these experts from the start will avoid frustrating errors and oversights and help the entire project team create the best possible collaborative plan before construction begins.

The right plumbing engineer also can offer valuable insight that is specific to a particular project. Plumbing and pumping considerations are dictated by the intended use of a structure. When designing a single-story retail outlet, the plumbing needs will be vastly different than those demanded by a mixed-use, high-rise building. Hospitals and other health care facilities often require plumbing to deliver medical gases.

While building exteriors get the glamorous curb-appeal shots and an interior designer’s dazzle, no structure is going to satisfy its occupants if the plumbing is substandard. Including the plumbing engineer from project conceptualization to completion will ensure that this critical system meets everyone’s performance expectations and serves the needs of the structure throughout its lifecycle.

Figure 1: The integrative design process includes all aspects of a building project, and all of the key partners in the project. Because the process is ongoing, all parties should be discussing all aspects throughout the project. Courtesy: WD PartnersFor example, imagine a 1-story office building design that is ready for engineering design to begin, but without input from an engineer. When the plumbing engineer gets the plans, he sees that the catering kitchen, restrooms, and natural gas-fueled hot-water tank are all placed on the north side of the structure. All of the service lines enter the building on the south side.

If the building’s engineering design proceeds with no input from the plumbing engineer, the design of plumbing systems may result in a less optimal layout and an increased cost for more materials and labor. Over the course of the building’s lifespan, inconveniently placed plumbing equipment can mean greater expenses for eventual repairs or general maintenance.

Suboptimal placement of restrooms and kitchens can lead to an overall system that underperforms or jeopardizes other parts of the facility. For example, a wastewater line that has to run the span of the building to reach its evacuation point will be more vulnerable to clogs or breaks. Instead of being isolated at the point of exit, wastewater and other contaminated material can put the whole structure at risk in the event of a failure.

The single-use, 1-floor office space used in the example clearly requires thoughtful planning. Specific-use facilities like hospitals and mixed-use high-rise buildings that populate many urban centers demand it.

Integrating all systems

Instead of designing a building in a bubble, an integrative design process model enables the lead architect to prepare all individuals, at the start of a project, to execute that project. At this point, the building is little more than a concept. With all players at the table, the plumbing engineer and the civil engineer may discover that thoughtful placement of a kitchen in relation to an existing sewer lateral may substantially reduce excavation depth or length of drainage piping.

Figure 2: This illustrates integrative design for sustainable systems. A rainwater harvesting collection and pumping system is coordinated with the location of plants to reduces piping and complexity. Courtesy: WD PartnersIn a design-build model, a general contractor may be represented in the early stages as well. The contractor may recognize a site-planning issue that can be alleviated by some site realignment to allow for a sewer lateral or a grease interceptor.

The goal behind the integrative design process is to challenge design assumptions. Inviting the plumbing engineer and plumbing contractor to the design table early in the process—along with all other disciplines—may open a dialog that explores the implementation of plumbing and piping systems and the integration of those systems into the building’s design.

From the start, the integrative design team seeks to identify and capitalize on synergies within building systems to maximize building performance, exceed building requirements, and deliver lasting value to the owners and occupants. The process leans heavily on the design-build model of project delivery, as opposed to the more traditional design-bid-build method.

Under the design-bid-build model, the contractor is not part of the integrative process. An approved design might solicit several bids that all come in over budget. At this point, several things can happen. The owner can continue with the project and accept the higher price tag. The architect, depending upon the type of structure, may propose a scaled-down version of the same project or suggest a plan that is built in phases. The originally approved design also may be scrapped entirely, often labeled as “value-engineered,” leaving the project right back at the starting point. If the project does move forward in some form, there may be some disappointed parties when the final product is delivered.

By eliminating the bid component, the design-build model favored by the integrative process streamlines the steps necessary to get from the design phase to the construction phase. The team members assembled in the design phase—architects, engineers, contractor, owner, and other stakeholders—will all continue to participate in the construction phase. As a result, there is no need to subject a preliminary plan to bid. The plan that comes out of the integrative design process is ready to be executed by the parties who crafted it, and they are prepared to operate within a budget they helped establish.

LEED v4 in plumbing projects

The integrative design process is now a required prerequisite in health care applications for U.S. Green Building Council (USGBC) LEED certification for a commercial building project and is available for a 1 point credit in most other LEED building classifications. Additionally, one of the key components to LEED v4 is consideration of efficient water use.

For these reasons, it’s best to get a qualified plumbing engineer involved in the integrative process. By successfully following the integrative process guidelines crafted by the USGBC, the engineering team can deliver a better product for the end user. Following the integrative process may require more time, effort, and creativity than a traditional project design, but the benefit to its implementation are many, for all stakeholders.

Figures 3 and 4: These schematics show two variations for harvesting rainwater for nonpotable use, such as for irrigation or in toilets.When used for a project with LEED certification or other sustainability goals, the early collaborations allow for more innovation and creativity with sustainability strategies. Most engineers have some experience in working with a client who decides very late in a project’s design to pursue LEED certification. The early and periodic collaboration involved in an integrative process eliminates the potential for the last-minute scrounging for LEED points. Rather than spend valuable project dollars buying renewable energy credits at the end of the project design, those project dollars can be used in designing sustainable systems, such as rainwater harvesting for irrigation or for toilet flushing.

Design and construction professionals interested in enhancing their credentials can benefit from a robust implementation of the integrative process. The USGBC now offers a one-point credit toward LEED certification when an integrative design process is utilized .

Case study: Harvesting rainwater at a school

An example of an integrative design process was performed for an elementary school in the Midwest. Sustainability goals were openly discussed during early planning stages. The client, a local school district, was pursuing U.S. Green Building Council LEED silver, and the existing building provided good opportunities to design new sustainable systems. The plumbing engineer was included early in the process.

The building’s expansive flat roof allowed for the collection of rainwater. The design team worked together to develop two rainwater-harvesting systems; one for toilet flushing and one for irrigation.

Because the project was for an existing building, there were coordination and collaboration hurdles to overcome. Available space was limited. An existing mechanical room in a less-than-ideal location (not central) was the only available space for new equipment. With the use of an integrated design process, challenges were brought to light early, allowing the design team to work together to solve such challenges.

The plumbing engineer and mechanical engineer coordinated on what equipment could be redesigned to allow more space for equipment associated with the rainwater-harvesting system. To increase available space in that mechanical room, the mechanical engineer coordinated with the structural engineer and the architect to design new air-distribution equipment outside of the mechanical room on the existing roof. Such a decision required buy-in from the structural engineer to reinforce roof framing, from the architect to design pathways for new ductwork, and from the electrical engineer to provide power systems in support of the new equipment.

The client was involved in the process as well, encouraging the team to continue to innovate while contacting the local water and sewer utility to allow for the installation of nonpotable water systems inside the building.

The rainwater-harvesting system consists of a duplex packaged domestic water-pumping system, a storage tank with an ultraviolet water-treatment system, and a roof-drainage system feeding into the storage tank. The system includes a bypass in case excessive water collection exceeds the rate of toilet use. Water piping serving the toilets is labeled specifically for use as nonpotable water only and painted bright orange to distinguish it from potable water. Note that the use of nonpotable water is recognized by the piping industry, and now purple pipe is accepted as the standard color for reclaimed water inside buildings.

The reclaimed-water irrigation system uses a series of aboveground outdoor collection tanks. The architect and landscape designer collaborated with the plumbing engineer so that the tanks would be located in proximity to the building’s proposed outdoor learning lab. Students could use the reclaimed water directly from the collection tanks for feeding plants. The plumbing engineer calculated the rate and amount of storm drainage that would provide suitable water storage for the system and designed for a portion of the storm-drainage piping to collect at the storage tanks instead of the toilet-flushing system.

Without the integrative design process, which outlined target goals early in the development of the project’s design, and without all designers and stakeholders involved throughout, the rainwater-harvesting system would likely have been quickly discarded from the project scope due to its complexity. Because the integrative process was embraced by the entire team, the project proceeded to conclusion with, among other sustainable strategies, the rainwater-harvesting systems constructed and implemented into the building’s systems.


Kari Engen is a senior mechanical engineer with WD Partners