A request for information came from the plumbing inspector shortly after the construction contract for a renovated school was signed. It said, "All water piping is undersized per Massachusetts Code and must be replaced. Please advise."
A review of my design reassured me that I hadn't screwed up, and I responded that the pipe sizing was fine.
At a meeting a few weeks later, the inspector explained that the Massachusetts Code uses different "demand factors" for office buildings than for schools. Piping that had been OK for an office would be undersized for a school.
"I did not use the demand factors in the code," I replied. "I calculated all the pressure drops. The code allows the piping to be designed by an engineer's calculations."
"Actually," the inspector said, "I don't think that's what it says."
We took out the book and read: "The methods used to determine pipe sizes shall be the procedure in ... publication #1038, or a system designed by a registered professional engineer, using the computation outlined in Tables 1, 2, and 3."
"See," the inspector said, "the code says an engineer has to use the tables in the code."
"That wouldn't make any sense," I replied. "If that's what it says, only an engineer could design piping using those tables. That would mean that plumbers would never be allowed to size any piping. That can't be the intent of the code—on most small projects, plumbers size all of the piping, and they use those tables. There must be a typo in this new edition. The previous edition of the code says '... designed by a registered professional engineer or using the tables.'"
"I never read it that way before, but I guess that makes sense," the inspector said. "I'll have to call the state board and ask for an interpretation."
A few days later I received a message: "Hi, this is the plumbing inspector. I called the state board about that code question. They say it's not actually a typo in the code. That comma between 'engineer' and 'using' means 'or.' So I guess your pipe sizing is OK as long as your stamp is on it."
I wonder what Lynne Truss, author of "Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation," would say about that use of a comma?
Energy Economics Inc.
Newton Centre, Mass.