Yes, you do. And more often than you think.

There has always been a love/hate affair between engineers and contractors. The impression by many plumbing contractors is that the engineer is an idiot. In a room filled with contractors, you will hear:
  • “The plans are wrong!”
  • “Where did they learn how to be an engineer?”
  • “Every engineer should be required to install plumbing before they are allowed to design it!”
It may surprise some plumbing contractors to know that engineers often have similar glowing comments to make regarding their counterparts. In a room filled with engineers, you will hear:
  • “That idiot plumber doesn't know how to follow my plans!”
  • “That contractor's going to change it to get it right or he's not getting paid!”
  • “We engineer it to save the client money. Then they install it their own way costing much more than is necessary!”
Of course, both the contractor and the engineer realize that they cannot live without each other. Both have a job to do, and smart contractors and engineers let each profession do their particular job.

I have been on a number of high-rise construction sites where the plumbing contractor just installs the plumbing system in accordance with the plans. When you ask if they understand the design and how everything operates, the answer is typically, “Heck, no, I don't have to. That's the engineer's job. All I have to know is how to install it the way it appears on the plans.”

If the construction project is running correctly, that is how life should be. The engineer should design it, and the contractor should simply install it in accordance with the plans.

Life, however, isn't always as it should be. Contractors are notorious for correcting what they view as the mistake that the engineer has made. The reason given for making such changes is that the contractor couldn't let the customer suffer with a bad system. Unfortunately, in many installations, that change may screw up the plumbing system and result in a failure of some sort.

I had one such occurrence recently where the contractor thought the engineer was nuts because the sizing would result in too high a velocity. So he increased the size to correct the engineer's mistake. The funny thing is that the connection to the piece of equipment was the size that the engineer had specified. Well, as you can imagine, when the system was tested, there was noise and vibration like you wouldn't believe. Guess what the contractor had to do?

This was a case where the problem surfaced right away. Normally, the problems occur a few years after the installation. If the system failure is due to a change in design not authorized by the engineer, guess who is responsible? You got it, and the payout can be large. If you install it in accordance with the engineer's design and it fails, now guess who is responsible? Right, the engineer. That is why they carry errors and omissions insurance.

What Can I Design?

A more serious problem has arisen with the re-piping, change in design, or renovation of an existing building. Most contractors take it upon themselves to just draw up a sketch and install the system the way they designed it. If it is for a single-family dwelling, in most states, that is not a problem.

Do the same thing for a commercial building, and in every state, you probably just broke the law. The Engineering and Architectural Registration Acts in each state clearly identify the design of a plumbing system in a commercial building as being the responsibility of the design professional. That means either a PE or an AIA. Yes, you have to hire an engineer to design even a simple re-piping of a plumbing system.

While you may not like this aspect of the law, it is still the law. If you violate it, the consequences are much worse when something fails.

To put the design law into perspective, imagine the general contractor coming to you and saying, “I'm going to have my laborers do the underground work since it is cheaper for me to hire them. You can continue the plumbing above the slab.”

You scream and say, “You can't do that. The plumbing licensing law says that a licensed plumber must install the plumbing and your laborers aren't licensed plumbers. Furthermore, there is more to plumbing than just laying pipe.”

To which the general contractor says, “Hey, this isn't rocket science. Anyone can install underground piping.”

In the long run, you win, because the plumbing licensing law supports you. Now, put yourself in the engineer's shoes when he hears a plumbing contractor say, “This isn't rocket science. I don't need a four-year degree, and letters after my name, to design a simple plumbing system.”

Yes, you do need the degree and letters after your name to design a plumbing system. There is often more to a design than just a bunch of lines on a sheet of paper. The engineer is trained and educated to fill in those parts of the design that you often overlook. The laws work for both parties. You need to respect the design professional laws as much as you respect the plumbing licensing laws.

Again, when the system fails, you become extremely liable because you not only installed a system that didn't work, you also designed it without the benefit of being a PE.

You may be wondering, “What can go wrong on some of these simple jobs?” Sometimes nothing. But, on other installations, I have seen quick bends on the outlet of a pump, improperly sized pumps, improperly sized valves, smaller diameter pipe than the connection on the pump, improper connections to existing systems, undersized piping, oversized piping, improperly parallel valve arrangement, oversized valves, etc.

To avoid these problems, bring in an engineer. They do cost money, but they also provide you with the protection of following the law correctly. Engineers are actually easy to work with. They are going to help you and they are going to work with you. Engineers are normally more than willing to build your preferences into their designs. Just remember that, since they are signing and sealing the drawings, they have the final say in the design. You merely have to install the system according to their design.