Our morning showers would not be the same without them. We sure miss them when they fail or run out of gas. Our water heaters are usually the silent worker in the back of the house; sometimes they are tucked away where we cannot see them however, they are a critical part of our plumbing system.
Most homes in Mexico use gas to heat water and rarely do we see electrical heaters. Typically, they are tank style heaters which heat up a tank of water so that the hot water is ready whenever needed. The volume of water in the tank is dependent on the demand or requirement of water for the house. Many two bathroom homes will have tank water heaters with a minimal capacity of 60 to 80 liters (16 to 21 US gallons) of water. However, some homeowners will require bigger tanks depending on higher demand such as large tubs, large washing machines, dishwashers, longer showers, etc. Tank water heaters have a limit as to how much hot water can be used and eventually the hot water will cool off as the tank empties. Hence the tank requires a recovery time to heat up the new volume of water that has entered the tank and depending on the manufacturer, size and configuration, which is usually between 20 to 60 minutes.
In masonry buildings with pipes, open over a roof, or hidden in walls and floors, there is heat loss over the length of pipe which can delay the arrival of hot water to the shower or sink. This heat loss causes a waste of time and water while you wait for the heated water to arrive. One key factor is the distance between the water heater and the sink or shower where the hot water is being used. If this distance can be minimized the heat loss or time/water wasted is lessened. In some cases, clients have installed more than one water heater to shorten the distance between the source and use and help eliminated the losses and increase the duration.
Some homeowners are considering changing their tank style heaters to demand style heater (tank-less system). The advantage of a demand style heater is that it eliminates the need to keep a large volume of water hot, heating the water only when needed; hence they are slightly more energy efficient. The hot water can be produced essentially forever, or at least until the gas runs out. The heat gained by the water is dependent on various criteria including the water flow rate through the heater, because of the size of the pipes in the heat exchanger in the heater and the amount of heat produced inside the heater.
The size of the demand heater is an important factor to consider. The maximum number of liters per minute the demand heater can produce defines the size of the demand heater. Units with higher flow rates have greater heating capacity, which is defined by kilowatts or BTU's. One of the popular sizes is a capacity of eight liters per minute. The maximum number of liters per minute is defined as a flow rate. If the water flowing out of the heater exceeds eight liters per minute, the water cannot be heated quickly enough to become hot and usable in the bathroom, laundry, etc. A flow rate of eight liters per minute is like pouring a cup of coffee every two seconds.
One problem I see with homeowners who have demand style heaters is their use of a higher flow rate of hot water higher than the capacity of the water heater. In one example, while filling the bath, the water flow rate was set at a capacity more than the demand water heater could handle and the client was frustrated with cool to lukewarm water for his bath. The flow rate was lowered to a volume of water that could be heated sufficiently but slightly slower than the maximum. If the flow rate is not satisfactory, likely the demand heater size is not sufficient for the use. Typical bathtub users will need a demand style heater with a capacity of approximately 16 liters per minute to handle the higher rate of flow to fill the tub.
