How does the boiler get hot water out of the tap simply by opening it?

How do the boiler and plumbing system in the house understand if we need to cold or hot water? The design and construction of the water-sanitary system is distinguished by the sizing and choice of various elements, including the type of boilerthe pipes hey special pieces that compose it. But how does the boiler understand when to activate only by opening the tap to the “hot”? In this article we address the topic starting from the path of the water from the external network to its actual exit from the tap.

How the water-sanitary system is made

First, we need to consider the fact that the hydraulic (or domestic water) system branches out, in its development inside the homein two distinct pipeswhich end in all the points where it is necessary to have a water supply, such as sinks, bidets, but also the washing machine itself. So, each exit point (called in technical jargon loading points), consists of two distinct tubes. Well, the two pipes they represent, distinctly, the flow of hot water and that of cold water. In fact, therefore, once the distribution point coming from outside (i.e. from the urban network) has passed, the tube is separated by a jointthus obtaining the desired path variation: one of the two branches will pass through the boiler, therefore through the element of the system that deals with the heat exchange guaranteeing heating; the cold water pipe does not require this passage and will therefore follow a different route, which does not involve the boiler.

How a boiler works and why the tap activates hot water

We now need to understand how it is possible to activate the boiler by simply opening the tap. This operation is done via specific objects present inside the boiler itself. Then, opening the tap to position “hot“, the water will begin to circulate outwards, simultaneously activating a sensor located inside the boiler. This sensor is directly connected to the pipe and is sensitive to the variation in speed of the water flow. There may be different types of sensors :

• THE flow switches(the most used ones) represent real switches: a cylinder arranged coaxially inside the water pipe, due to the thrust of the moving fluid, moves, closing an electrical circuit. This circuit generates a signal that allows the boiler to turn on. It then comes into operation and begins to heat the water through its internal thermodynamic mechanism. So, when the water is still inside the pipe because all the taps are closed from the side heat, the cylinder does not move and the electrical circuit is not able to activate the boiler.
• THE flow meters (or flow meters) are instruments that they also perform a flow measurementor the volume of water that passes through the tube per unit of time: inside the tube we now find a pinwheel which begins to rotate around its axis when the water is in motion. Based on how much rotation is generated, the flow rate can be indirectly estimated and, if necessary, the boiler’s energy commitment in heating can be adjusted, so as to optimize energy consumption. Unlike flow switches, flow meters are also widely used for other applications, for example for measuring consumption, water or even gas.

In both cases, the ignition – but above all the full operation – of the boiler does not occur immediately when the tap is opened. In fact, it takes time before the outgoing water is actually at the right temperature. This waiting time obviously depends on the efficiency of the boiler.

Being partly mechanical and partly electrical devices, they can be damaged and/or worn. In fact, sometimes the boiler does not turn on due to the incorrect functioning of these devices, which must therefore be replaced or repaired to restore correct operating conditions.

How the water temperature is regulated

The water temperature regulation takes place instead totally mechanically. Essentially, this adjustment is governed by us users based on the opening position of the tap. In fact, by moving the tap between the hot and cold sides, we create a bottleneck to the two flows of water and introduce them at the same time a mixture of hot and cold water which, together, produce an output flow with the desired temperature. The restriction can be total when the tap is turned to one side only. Obviously, the choked flow it will be exactly the one opposite to the position of the tap.