The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Saturday, February 24, 2001

Plumbing lessons

My friend Kurt (same one I went haunted house hunting with last year) arrived to help help us movie. He had just finished a class in checking back-flow prevention valves, which is actually more interesting than it sounds.

Kurt is currently a high school English teacher who is burned out—long hours a poor pay have taken their toll on him, so he's getting into the family business of plumbing. Only it's not plumbing as in plumbing repair, it's more like plumbing engineering.

Between hauling boxes and furniture up to the apartment he would stop and explain how back-flow prevention valves work. Basically there are three chambers. The first one is at a high pressure, say, 40 PSI. It hits a plate separating the first and second chambers and that plate has a spring holding it in place, but the spring has a much less pressure, say, 5 PSI. That means the water from the first chamber enters the second chamber but at a reduced pressure, which is the difference between the water presure of the first chamber minus the pressure of the plate; in this example, the water in the second chamber is now 35 PSI. There's another plate between the second and third chambers, and this one supplies even less pressure, say 1 PSI, so the water in the final chamber will only be 34 PSI.

Now, in the bottom of the second chamber is a diaphram, and water from the first chamber is directly allowed to fill the area below the diaphram. This pushes the diaphram up, because the pressure above is lower than below (35 PSI above, 40 below). Now, if the presure in the third chamber rises, it shuts the plate, causing the pressure to rise in the second chamber. This pushes the diaphram down, opening a valve to release the water directly out of the system instead of letting it build up into the system.

Quite interesting. And you have to be careful in checking some of these back-flow valves, especially the larger ones, as they can quite literally explode in your face if you're not careful.

Obligatory Picture

[It's the most wonderful time of the year!]

Obligatory Contact Info

Obligatory Feeds

Obligatory Links

Obligatory Miscellaneous

You have my permission to link freely to any entry here. Go ahead, I won't bite. I promise.

The dates are the permanent links to that day's entries (or entry, if there is only one entry). The titles are the permanent links to that entry only. The format for the links are simple: Start with the base link for this site:, then add the date you are interested in, say 2000/08/01, so that would make the final URL:

You can also specify the entire month by leaving off the day portion. You can even select an arbitrary portion of time.

You may also note subtle shading of the links and that's intentional: the “closer” the link is (relative to the page) the “brighter” it appears. It's an experiment in using color shading to denote the distance a link is from here. If you don't notice it, don't worry; it's not all that important.

It is assumed that every brand name, slogan, corporate name, symbol, design element, et cetera mentioned in these pages is a protected and/or trademarked entity, the sole property of its owner(s), and acknowledgement of this status is implied.

Copyright © 1999-2023 by Sean Conner. All Rights Reserved.