Every project is somewhat akin to a human body: Trying to cut off an “unimportant” part will cause the body to suffer - or even die.

Let’s begin by pinning the project drawing to a wall and looking at it for a moment. All walls are “soft” at this time, all lines are handwritten, even the size is not final. However, one thing is known for sure: This building shall have plumbing.

Let’s step back now and take another look. The building is proposed to be constructed on the street and the street is filled with the city’s utilities, which you are looking at now. There are all kinds of pipes, wires and conduits running under and over the street. Pipes become larger; they are interconnected, creating a sophisticated web. This piping web is a part of an even bigger picture called an infrastructure.

Infrastructure Questions

The plumbing part of an infrastructure contains domestic water, sanitary sewer, storm and gas piping. There are two initial questions to ask:
  • Does a system have sufficient capacity to support the proposed building?

  • How may the building affect a system?
If the first answer is no, we should start looking for alternatives. If the first answer is yes, we can move on to the second question (and further subquestions). Virtually each system will be affected by an additional load, and our task is to determine the acceptability of its impact. In other words, does it work?

The domestic water draw to the building may cause an excessive pressure will drop in the street main. Is it possible that the pressure drops to below the acceptable level? Is it probable? What can be done about it?

The sanitary main under the street or a sewer treatment plant may not have any spare capacity. What can be done about it?

The storm main under the street may not have any spare capacity, either. What can be done about it?

The natural gas capacity and pressure also are important. Is there a high-pressure main? May this pressure fluctuate if the demand suddenly changes?

Now that we have all our answers, and everything works, should we grab a red pencil and proceed with the design? Not yet. We must first reach for a calculator, figure out the budget and find out if there is enough money for everything. The simple fact that a system works does not in any way imply that a system is affordable. Count the $$$ now.

Good news! The budget works. Now is the time to grab the red pencil and look into the services.


The first in line is the Domestic Water Service. This service is essential because potable water is required in all buildings “with plumbing fixtures and used for human occupancy.” Also, it is nice to be able to drink water right from a faucet without any worries.

Water provided to the building must be metered. Should we design a meter pit outside of the building or is it allowed for a meter to be located inside? This question is for a water company to answer, but don’t forget to ask. Typically, a water company’s design manual describes the type of the meter, its preferred location, installation details, remote reader requirements and even the manufacturer’s name.

All clear with the meter? Good. Now is the time to begin with the piping layout, right? Wrong.

Let’s step back and imagine (maybe even guess) what may be installed on the end of a pipe. A fixture or a piece of equipment connected to a potable water system may be a source of contamination. As a result, now is the time to evaluate these possible contamination sources and classify our building based on the degree of hazard it may present.

Backflow prevention may be required at the service in addition to backflow preventers provided at each potentially hazardous location. The water company’s design manual may be helpful again with directions as to how and where to install the backflow preventer. However, we also need to check local building and health department requirements, as well as the county and state health department requirements. Does it look like extensive research? Well, it could be.

Next is the Sanitary Sewer. What goes in must come out and be piped to the street main (we already know that the main will be able to accommodate our building).

Can it be done by gravity? A sewage ejector, if required, may become a designer’s challenge.

Is there a kitchen planned for the building? Think about a grease interceptor, but don’t design it. Check on your local resources.

Storm Main. What can be easier? There are drains, leaders, mains and a lateral to the street. But let’s step back once again and look at the Big Picture - at the building site, grades and access roads. The ground floor elevation may be below the street main, and all this rainwater running toward the building must be stopped and retained (some municipalities may require 100% retention) or a storm ejector may be required.

Civil engineering and landscaping are not in our scope of work. Do we need to know about the ejector? Of course! The fact that the forced storm main may exist next to the building will require careful coordination between design team members. Connections of forced and gravity mains should be arranged properly, the street main should not be subjected to an excessive surge when pumps will start, and remember to remind your electrical engineer about the power required. Anyone’s mistake may cost $$$. Your client suffers no matter whose mistake it is, and the entire team does not look all that good. Remember the team.

Finally, there’s Natural Gas. It is available, we did check on it (otherwise propane may be considered, or oil). We need energy; no building can exist without an energy source.

Usually a gas company provides the service, including an excavation and a meter installation. Initially, it looks like we don’t have much to do with this one. But take another look. We must indicate the location of the meter. Team effort is required again - coordination with the architect (appearance, doors and windows), the HVAC designer (air intakes), the electrical designer (electrical service and transformer locations) and other utilities. 

The next step is to write a letter to the gas company with (at least) the following: an estimated load, including possible future expansion; the pressure required; and a copy of a site plan with the proposed meter location.

Okay, all services are in place now. It’s time to draw! Or is it?

Step back again and look at the building. The “soft” walls are getting ready to become “hard” and space planning is in progress. Now is the time to allocate mechanical space and make sure we have all the shafts required.

What shall dictate how much space we need? Now is the time to choose.

Fixtures & Equipment

Decisions, decisions, decisions ...

Budget probably has the most serious impact on the decision process. Ask the owner if he has any standards established already. A simple question can save you some serious footwork. What if the answer is no? It may be a good idea to put together a set of cuts as early as possible to give the owner and the architect enough time to review your selection.

Now let’s talk about selection. At a glance, there are not too many choices for a commercial application. However, many “little” things shouldn’t be missed if you wish to have a truly functional system. Ask questions and do not be afraid to ask stupid questions, because there is no such thing.

Just a few samples:
  • Is this water closet handicapped? Is a bedpan washer required?
  • Is this lavatory considered public? What type of metering faucet is preferred?
  • Is a disposer required for the kitchen sink? A hot water machine? A chiller?
  • How fancy do you wish to make your shower? Add a thermometer? A light?
The equipment selection process appears to be less complex. After all, we are the engineers paid to make this selection, true? Yes and no. The correct answer is: We are paid to make the “right” choice.

But what is “right”? There are few “rights” for any project:
    1. All equipment must conform to appropriate standards, be functional and energy efficient.

    2. Each and every device should be suitable for a purpose. A water heater for a school with high demand during breaks could be (and should be) quite different from an office building water heater.

    3. Life expectancy should be reasonable. Hospital equipment must last longer than residential.

    4. Sizing must be reasonable as well. Medical air compressors must be fully redundant and oil-free. This rule does not apply to an industrial compressor.
All set with your selections? Fine. In Part 2, we'll turn to the drafting table and figure out what we need to include to finish this design.