the bblog

leak testing

Lately I've been checking for leaks. How does one do this, you ask? Easy!

Check system pressure at the EP box, where each floor taps compressed air from the central air line. 19 times out of 20, pressure will be nominal, maybe a pound below central pressure.

One time out of twenty, though, system pressure will be outside of tolerances, and you have to proceed to the actual leak checking phase of the operation.

Now, at two union, the system air is piped to a loop that circles the floor, with taps where perimeter fans and thermostats draw air from it. Everything is operated by air, of course, because two union was built in 83, before the invention of electricity.

To test for leaks, you cut the loop right by where central air is connected to the loop, but before it is tapped to power a thermostat/perimeter box, since this would isolate it from the loop, and thus render it nonfunctional. This isn't bad, in the sense that this is done all after-hours, and thus with nobody to complain about the heating suddenly not working, but bad in the sense that you can't test a box for leaks if it's not connected to the loop.

Anyway, once you cut the loop, you go halfway around the floor and connect a gauge to the line. You then squeeze shut the line directly after the gauge, and if system pressure goes up, you know that the leak is somewhere after farther down the loop. If it doesn't go up, then the leak is farther up the loop. By doing this over and over, you can narrow down the location of the leak enough that you can just trace the line by popping up ceiling tiles, which would otherwise take far too much time.

This is idealized scenario, of course. What actually happens is that when you plumb in the gauge halfway around the floor it will read one PSI, stubbornly refuse to budge from that reading no matter where you clamp the line, and then strongly insinuate unkind notions regarding your mother's reputation.

Dejected, you will wander the floor at random, immediately stumble upon the leak, (a contractor cut a branch but was too lazy to plug it) fix it, and hurry to your blog to tell the world about how awesome you are.