Commercial building retrofits may require field verification from all disciplines: architectural, structural, electrical, mechanical and plumbing, to name a few. While plumbing retrofits have limited amount of scope for other disciplines, there are aspects of these projects that increase the potential for both the scope and complexity of the project for others.

This article focuses more on the plumbing aspect of these retrofits and how it may not be as simple as you think.

Taking a step back, retrofits are a small part of the bigger picture — in this case, a building. A building may have been built years ago with system designs that are no longer sustainable, relevant or up to code. Rather than tearing down the entire building to start anew, clients have the option to select the kind of layouts and updates that best fit their tenant improvement project. 

A tenant improvement may be a whole or partial redesign of the existing floor plan layout or system. This may include, but is not limited to, additional, removed or shifted restrooms, breakrooms and equipment rooms. In the case of a retrofit, the floor plan or fixtures themselves may be improved with designs that achieve increased building efficiency. 

Building efficiency becomes increasingly important as more modern buildings are rising, leaving the existing structures to catch up in terms of environmental impact and sustainability. Many projects opt to pursue LEED (Leadership in Energy and Environmental Design) points, a measuring tool to determine a building’s efficiency through all disciplines by costing less to maintain and producing less waste. For plumbing retrofits, this means considering strategies to reduce both water and energy consumption. 

However, there are challenges associated with designing a commercial plumbing retrofit.

• Documentation accuracy. The plumbing engineer and designer must gather as much data as possible regarding the existing building and utilities. Knowing the history of the building gives the designer an initial vision of the current plumbing system. This allows the designer to determine whether the existing system can accommodate the new function of the building. 

Drawings and calculations may also vary greatly from what has been installed, so field verification is important when possible. Original and subsequent renovation plans were likely produced using different software or designed by hand. Even with those plans, the installation may not have strictly followed the plans as unforeseen conditions in the field may not be transferred to record drawings.

• Compliance. As plumbing codes adapt and update over the years, older designs may no longer comply with applicable codes. With partial tenant improvement projects, noncompliance can pose a challenge if one or multiple areas being redesigned are no longer up to code. 

• System sizing. Modern designs and layouts do not always fit within an existing system. For example, a new core restroom may be upgraded from the original flush tanks to flush valves. Flush valves, however, require higher water pressure and larger pipe sizes, potentially forcing a larger system redesign. 

3D Scanning, Sanitary Vacuum Systems

Technology can be used to verify what is installed in the existing space. For example, in the Banner Thunderbird Medical Center 6th Floor Buildout, a 3D laser scanner identified the location of existing piping (see Figure 1). Patient room waste and vent piping rough-ins had already been installed to match the level below, but the retrofit architectural layout relocated part of the rough-in, promoting better hand hygiene and helping reduce the number of possible incidents of health-care-related infections. 

To avoid disruption of the level below, the design team routed the waste within the wall horizontally to connect to the existing riser stacks, requiring close coordination between the architects, plumbing and construction team to ensure the design was both constructible and code-compliant. Having informed data to fully understand existing conditions helped the team to think through the solution in advance and subject the feasibility of the proposed method. 

It also allowed the team to respond effectively to the following questions: Can it be built? Can the pipe move? What is the impact on the floor below or above? How would this impact nearby disciplines?

Another technology that can significantly help a retrofit process is a sanitary vacuum system (see Figure 2). A sanitary vacuum system is an alternative to saw-cutting the existing floor slab. While a sanitary system drains by gravity with the pipe sloping downwards, a sanitary vacuum system draws sanitary waste up vertically into the ceiling above using the vacuum system, allowing the system to slope using gravity to connect to a nearby sanitary pipe. 

However, not all local jurisdictions allow the use of sanitary vacuum systems. This is true, especially in California, where some local AHJs (Authorities Having Jurisdiction) do not accept such systems. The plumbing engineers must verify and educate themselves on the approved methods in the project’s location prior to suggesting alternatives.

Fixture Upgrades

Over the decades, plumbing fixtures have been advancing based on the need for continuous sustainability of the commercial market and the advancement of technology. Below are a few plumbing fixture upgrades regarding a retrofit.

1. Manual to Automatic Operation

• Upgrading manual fixtures to automatic fixtures has become more common in previous years, even before the COVID-19 pandemic. The upgrade from manual to automatic fixtures tends to happen with the restroom fixtures. 

• The best practice when it comes to restroom designs is to promote and assist with facility maintenance that supports minimizing hard-to-clean surfaces, ease of repair, easy access to components and providing standardized components for ease of part replacement.

2. Flush Tank to Flush Valve

• A building with an existing flush tank converting to a flush valve requires a higher water pressure and a bigger pipe connection to the fixture. The existing conditions of the current building water demand are crucial as to whether the building can handle the upgrade to a flush valve fixture.

3. Floor-Mount to Wall-Mount Water Closets

• Using wall-mounted fixtures provides some flexibility with the installation. This is especially important if the building floor slab is constructed as a post-tension slab or waffle slab. 

A post-tension slab uses high-strength steel cables laid out in a crisscross grid pattern within the poured concrete, while a waffle slab has a flat-top finish with a grid pattern of reinforcing concrete beams beneath. A wall-mounted installation is also easier to clean as the floor below is open.

• A floor-mounted water closet with a bottom outlet would require two slab penetrations, one for the sanitary and another for the vent. This would lead to other challenges if penetrating on or near the reinforcing cables or a concrete beam. 

Instead, by using a wall-mounted water closet, there is only one penetration for the sanitary line. The back outlet option allows the sanitary piping to run horizontally within the plumbing chase, providing more flexibility when designing the sanitary system. 

• There have been floor-mounted water closets with back outlets designed and installed and a model designed specifically for retrofitting. This type of water closet would function the same as a wall-mounted option, yet with a different aesthetic design.

The existing piping itself should be verified by asking these questions: What are the existing pipe materials? Do the existing pipe materials meet the current code and allowed to be used for the retrofit? 

An instance of a code requirement causing a pipe material replacement is if the project must adhere to the California Department of Health Care Access and Information, formally known as the Office of Statewide Health Planning and Development, where PVC piping is not permitted. 

Floor or Room Function Changes

The piping material requirements may also change as the function or type of floor and rooms change. If the function of the building changes from an office to a lab space, laboratory waste may be required due to the function of the laboratory. In that case, the lab must be studied to understand the specific type of pipe material that can handle the possible chemical waste using chlorinated polyvinyl chloride, polypropylene piping, etc.

An example where the building function completely changed is the Mountain Park Health Center in Tempe, Ariz. (see Figure 3). The original 32,000-square-foot boat dealership was retrofitted into a new ambulatory clinic to support the community. The innovative design considered the voices of the community to transform the space into a modern and inviting establishment. 

The roof was modified, requiring a redesign of the primary roof drains collected at the stormwater retention onsite while maintaining the majority of the overflow piping within the building. The sanitary sewer system was a complete redesign, providing a new point of connection to the city sewer to accommodate the drainage fixture load of the new building function. 

This new clinic improved an outmoded structure by providing a sustainable design that promotes health and wellness. Its efficient systems design uses best practices and updated low-flow fixtures to minimize environmental impact.

When it comes to plumbing retrofits, the design may not be as simple as demoing, replacing and adding plumbing fixtures. There are many challenges to consider when designing and engineering a plumbing retrofit, which range from understanding existing conditions to ensuring code compliance to choosing the right process for each of the plumbing systems. 

Systematically stepping through these challenges allows the engineer and designer to identify the impacts and provide an efficient, sustainable and cost-effective plumbing solution for the retrofit space. 

Megan Hessil is a plumbing engineer at SmithGroup’s Phoenix office and a member of the American Society of Plumbing Engineers (ASPE). Lhymwell Manalo is a plumbing designer at SmithGroup’s Phoenix office. He is a member of ASPE and has six years of experience designing plumbing systems for various building types.