Sustainability has been a very hot topic for a long time. In the plumbing engineering community, my impression is that sustainability often focuses on water conservation, which is a controversial topic these days. With Legionella growing (see what I did there) into such an important topic, water conservation has partially become the enemy of Legionella mitigation practices.

As plumbing engineers, we should be looking at other ways to employ sustainability in our designs, without contributing to the development of waterborne pathogens and putting building occupants at risk.

One area is how we size systems. What methodology are we using in developing our pipe size design criteria? What are we obligated to follow based on the enforced codes?

Downsizing our pipe sizing practices has a direct correlation to the amount of material used on a project, and results in overall water savings. The best part — it’s a great Legionella mitigation practice. Less total water volume and less surface area equals a lower risk of waterborne pathogen development. We need a continued effort in pressing code officials to adopt more modern domestic water pipe sizing practices.

As plumbing engineers, we should be looking at other ways to employ sustainability in our designs, without contributing to the development of waterborne pathogens and putting building occupants at risk.

Another method is in the way we design systems. There is an old saying “The shortest distance between two points is a straight line.” So, are we being efficient in our piping layouts? Can we eliminate a few extra turns, jogs or elevation changes? Can we stretch a pressure zone an extra floor? Can we think about hot water return systems differently such that we can localize reheating of water to reduce long runs back to central systems?

Using less material reduces our overall carbon footprint as well. If less material is used, we reduce mining/manufacturing and/or recycling energy for metallic-based pipes and tubing. For any plastics used, we save on material use and energy consumption. In both scenarios, reduced materials allow for a reduction of direct impacts and emissions related to transportation and installation.

In addition to using less material overall, the materials chosen for a project play a key role in overall sustainability. Moving toward a sustainable design means learning how to:

• Use materials that consume less energy in the production process compared to others;
• Use materials that can perform the same job with less. Fewer fittings, joints, etc. equals less energy used in installation;
• Use materials that are lighter than others. This lowers transportation energy consumption, and energy during installation; and
• Energy savings due to thermal insulation — i.e. do not conduct heat (in or out of the pipe wall) as quickly as another material.

You might immediately think that plastic piping over metal is the optimum choice. And, in many cases, this is a true statement.

When looking at materials, the carbon footprint is what tops the list for determining overall sustainability. The carbon footprints of plastic products are determined by the measurement of emission of Greenhouse gases in the whole production process. And a key factor in reducing greenhouse gas production in the development of plastic piping is recycling. In the case of PVC, recycling can reduce the climate impact from 36.21% to 15.53% alone.

The life cycle assessment is a great way to measure carbon footprint. If one were to look at a life cycle assessment of PEX compared to copper in a domestic water supply system, one would find that PEX has less than 1/3 of Global Warming Potential (GWP) and Ozone Depletion Potential (ODP) compared to copper, over a 50 year lifetime. The same can be said for PVC compared to ductile iron in a drainage system. PVC has less than 20% GWP compared to ductile iron and less than 70% of ODP.

And even amongst plastic, there are winners and losers. PVC has higher energy consumption and CO2 gas emission that shows its high potential in global warming compared to other plastics. However as mentioned above, recycling can reduce this significantly.

Equipment

When we think of sustainability and equipment, energy consumption comes to mind first. And rightfully so. Anything we can do to increase equipment efficiency and/or utilize a clean energy solution to power plumbing equipment is the right way to go.

What’s important is how we, as engineers, push our industry going forward. A few ideas we are reviewing at our company are:

Establish a company plan:

• Provide in-house training to inform staff on carbon-reducing design tactics and embodied carbon calculation methods;
• Develop design guides related to equipment selection reducing operational and embodied carbon;
• Develop training tools for business development, project management and other client-facing team members on “selling” carbon-reducing designs; and
• Review detail and specification content, update to promote a reduced carbon specification.

Request low GWP refrigerant:

• Develop training on low vs. high GWP refrigerant choices;
• Develop in house list of manufacturers/equipment and update specifications to reduce use of high GWP refrigerants; and
• Update specifications to include equipment selection of low GWP refrigerants.

Request EPD (Environmental Product Declarations):

• Contact frequently specified manufacturers to gain an understanding of current carbon and refrigerant use and disclosure practices;
• Update specifications to request manufacturer disclosure of refrigerant type, amount, and efficiency as part of the submittal package; and
• Provide gentle communication to manufacturers that your company’s position is to reduce carbon footprint, and you are focusing on manufacturers supporting this goal in your specifications.

We can play a big part in our designs right now towards a more sustainable future. And with good material selection, and pushing out industry to do better, we can have this future in hand much sooner than we think.