Beads in pipes?
May 19, 2016 12:50 PM   Subscribe

It often sounds like there are little beads or ball bearings rattling around the pipes in my workplace. Why?

I work in a building where scientific research happens, so in addition to the usual hot and cold water pipes, there are lines for compressed air, nitrogen, vacuum, natural gas, and possibly others. In some sections of the basement with exposed pipes, I can often hear what sounds like many beads or ball bearings rolling quickly in the pipes. It's loud! Anyone know what could be in there?
posted by tchemgrrl to Technology (11 answers total) 3 users marked this as a favorite
Water hammer?
posted by likedoomsday at 12:55 PM on May 19, 2016

Thermal expansion/shrinkage during temperature shifts?
posted by jon1270 at 1:05 PM on May 19, 2016

Pneumatic tube system?
posted by SLC Mom at 1:08 PM on May 19, 2016

posted by sparklemotion at 1:39 PM on May 19, 2016

Steam pipes can make some weird sounds which are I think pretty standard. You don't mention steam but maybe?

A theater I worked at had a sound like a bunch of very tiny ball bearings that came from a large hot water pipe. It stopped one day and we later found out that some patch work was done which removed the noise. There was some issue that was allowing air bubbles into the water and that was causing the noise. I don't know how the air got in or how it was stopped, sorry.
posted by Clinging to the Wreckage at 1:58 PM on May 19, 2016 [1 favorite]

When I worked at the World Trade Center, I'd eat my bag lunch in a closet full of risers. Pipes of various diameters. It was like sitting next to some weird musical instrument. A lot of these pipes were very long. The water pressure was pretty high. There would be constant tinking and clanging. When asked, my boss said that the sounds were cause by tiny bubbles. Even the loud ones.

Then he told me to eat in the lunch room or else.
posted by Splunge at 2:07 PM on May 19, 2016 [5 favorites]

My hot water baseboard heat makes that noise. I discribe it as a broken glass sound but I'm sure it's the same thing. My handyman says it needs to be "bled" of the air in the lines. I thik they just open a valve and let the water run out until there is no more air in the line.
posted by BoscosMom at 3:44 PM on May 19, 2016 [1 favorite]

I used to have to bleed my radiators (still have a little key for that), so could imagine all kinds of lines are prone similarly. Maybe that puts the flicker in your Bunson burner...
posted by acm at 4:13 PM on May 19, 2016

I think it's cavitation, the same thing that makes your joints crack when you pull on a finger.

The reason it happens in the basement is that in a drain pipe full of liquid all along its length, the liquid coming out of the bottom of the pipe as it enters a wider sewer pipe cannot come out any faster than liquid which is flowing through the pipe at any point along its length, despite the fact that the water coming out has given up a lot of potential energy on the way down, and this causes the water toward the bottom to 'pull' on the water higher up, which in turn cause a pressure drop in those parts of the pipe, resulting in cavitation.

You can see the effects of this lower pressure at the top of drain pipes in the hole that develops in the surface of water in a full sink a little after you've pulled the plug and the drain is full of flowing water, because the air/water interface is where the water pressure equals atmospheric pressure, and when the pressure in the pipe falls below atmospheric pressure, as it often does, the pipe begins to suck air and gurgle even though the sink may still be partly full.
posted by jamjam at 4:21 PM on May 19, 2016 [1 favorite]

We have some pipes where I work that are suspended high from the ceiling and they always made this strange noise like tiny marbles were rolling down it, to me.

I finally connected the fact that they were probably water pipes because every time someone would flush in a restroom, the same creaky noise would happen, but it was actually just the pressure movement of the pipe itself creaking, and rubbing up against the hanging fixtures..
posted by Quarter Pincher at 8:33 AM on May 21, 2016

I got an answer! Turns out there is a central vacuum system that is used to clean out, among other things, pellet-like animal bedding, and it's the sound of the pellets whizzing towards the exit. My less biological background had me thinking about molecular sieves keeping nitrogen lines dry, but the real answer was considerably more prosaic.
posted by tchemgrrl at 6:24 AM on July 6, 2016 [2 favorites]

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