Why is it that in every community of neighbors there is one who enjoys moving furniture at odd hours and another who loves playing marbles? Science has no explanation for the first, but it does for the second. And it is that, in reality, when we think we hear a rattle of marbles on the floor above, it is not exactly that. Actually, it is the sound of the pipes subjecting to a phenomenon of physics known as water hammer or Zhukowski pulse.
This occurs when a faucet or valve is suddenly closed . It can happen at any time of the day, although we tend to hear that sound of marbles more at night, basically because everything is silent.
It is something very normal, that is why practically all of us have heard it at some time. In principle, it does not entail risks, although it is true that in some situations it can be dangerous, since it would indicate a situation that could end up with the pipes bursting . Anyway, before we get to that point, let's go to the origin: why do we hear that sound of marbles?
The Zhukowski pulse and the noise of marbles in the pipes
Fluids generally have a slightly elastic behavior. Therefore, when water runs through the pipes and a faucet or valve is slammed shut , a curious effect occurs. The particles that were approaching the point that has been closed stop abruptly. However, the ones that came behind keep moving to the point of colliding with them. This gives rise to a kind of rebound, with which the water occupies the vacuum that had been generated behind it, expanding the air towards the edges of the pipes. As a result, the pressure increases and they tremble, producing that rattle similar to the sound of marbles.
It is important to note that this does not happen only when a faucet is turned off. It can also happen when a valve is closed at the moment that a washing machine or a dishwasher stops drawing water.
It could be dangerous?
The entire phenomenon of water hammer is accompanied by a sudden increase in pressure that in certain circumstances can be dangerous.
For example, during vacation periods, when there are fewer people living in the building, there are more valves and taps closed, so it is more difficult to relieve that pressure. As a result, after the rattle of the marbles the pipes can burst. And not only that, the taps and valves installed in the building can also break.
The danger increases during vacation periods, when there are fewer people in the buildings
Fortunately, there are some mechanisms to prevent water hammer from becoming dangerous. For example, it is important that fluid particles do not move too fast . To achieve this, the diameter of the pipes is played with, until adequate speeds are achieved.
On the other hand, seat valves can be used, which stop the flow of water in the pipes more gradually than conventional ones. Thus, the suddenness that can lead to water hammer is avoided. In the same way, other elements capable of absorbing the pressure waves that generate this effect can be used.
In short, if you hear that characteristic sound of marbles, it is actually the water making caroms in the pipes of your building. The plumbing system should be prepared to absorb this pressure, so in principle there is nothing to fear. You can simply stop thinking that your upstairs neighbor has some weird hobbies. Or maybe he is a fan of traditional children's games. It is somewhat less likely, but it could happen. However, we are not here to judge you.
