A hydrometer is an instrument that measures the density of a substance. Explaining how it works may be easier to understand using a hypothetical example in which a human being is a hydrometer.
Let’s say you’re in a hotel that has two pools. One pool is freshwater, while the other is saltwater. You enter the freshwater pool and carry a water-resistant marker with you. No one else is in the pool; the water is still. You get into the deep part, slowly and carefully to alter the surface as little as possible. You shake the water very little, and you only make enough movement to keep it upright. Once you are no longer floating up and down, you mark your skin with the down just at the level that the water reaches. Let’s suppose that, due to your particular body mass and your overall complexion, the mark remains on your chin.
Now you enter the saltwater pool in the same conditions and repeat the whole process. The mark you make in the saltwater pool will be lower in your body than in the freshwater lake. Why? In this hypothetical example, you have just demonstrated that fact by representing a human hydrometer. A hydrometer will not sink as deeply into a dense liquid as a less thick liquid.
The actual hydrometers or densimeters that are produced vary slightly in their design, but a typical example would be one the size of a pen. It is a sealed glass tube with a weight of ballast at the bottom (possibly mercury or lead). The upper part of the hydrometer – the piece that floats up and down above the surface of the liquid – has a graduated scale inside. This allows the user to place the hydrometer in the liquid, wait for it to remain at rest, and then take a reading that will indicate the density of the liquid.
The density meters are useful in many applications. An exciting one is the finishing of maple syrup. After the maple sap has been boiling and has just reached the correct density to be called honey, a hydrometer that is deposited will float to a specific level. If it drifts too low, the sap has not evaporated enough water and is still too light and thin. If the hydrometer floats too high, the honey has become too thick and dense, and the maple producer will probably have to turn it into something else, like maple sugar candy, instead of maple syrup. The hydrometer should give a reading that is fair to the proper density for maple honey. The hydrometers are used in the preparation and elaboration of wine and many other industries.
In the standard conditions that a hydrometer can operate, we have the nominal flow, being expressed in cubic meters per hour.
However, the hydrometers may have a below-expected, ineffective measurement, called sub-measurement. We can cite as the most common causes:
- Inadequate installation conditions;
- Low or high operating condition;
- Incorrect sizing;
- Lack of maintenance
- Error reading (human factor)
- Supply conditions
- Shelf life expired
Therefore, to avoid measurement errors that will influence the billing later, a forecast is made considering the type of hydrometer, consumption, and their respective nominal flow.
If it is identified, for example, that many water meters are near the end of their useful life, the sanitation company can establish a hydrometric plan.
Consequences of lack of water meter
We have in our country many municipalities that do not yet have a hydromassage plan. This means that many do not have a consumption measurement system.
The latter is the case in the city of Ouro Preto, which has no water meters for most of the connections. That’s what you imagined; the water is not charged!
What happens, for this reason, is the irrational consumption of water.
It reaches the point of 550 liters/day per inhabitant, taking into account production per inhabitants. If we compare with the neighboring city Itabirito, where there are water meters in the residences, the expense is 167 liters/day.
It is noticed that there is rationing when the bill has to be paid, and yet both are above the average recommended by the World Health Organization (WHO) that is 110 liters/day per person.
In September 2018, the use of the minimum flow rate was registered in the system that supplies 60% of the population, since the need of the community can no longer be met due to lack of rain and the already mentioned excessive consumption.
The authorities must understand the need for a hydrometric plan and the awareness of the population.
How has consumption been in your municipality? Is there a hydromassage plan? What is needed to optimize resource usage and billing?