Water heaters are an appliance we rarely think about, until there is a problem. Whether your water heater is leaking, making noises or just stopped working, we can help you diagnose and repair the problem.
Water heaters are not really all that mysterious. A water heater heats water on a continual basis, whether you are using hot water or not. When you draw off hot water, cold water enters the tank to replace the hot water drawn out. When the thermostat senses the water temperature has dropped below the hold level, it initiates the heating element(s) in an electric water heater or the burner in a gas model. Even if you don’t use hot water, the temperature in the tank will fall and so the water will be periodically reheated to bring it back up to the desired temperature. Because of this wasted energy, it is advisable to turn down the thermostat when away for extended periods of time, such as when you are on vacation.
Which Water Heater is Better: Gas or Electric?
Gas and electric water heaters are about equally common. An advantage of electric is that they don’t require venting of the combustion gases as in a gas model. However, electric heaters may be more expensive to operate and generally don’t heat cold water as quickly as gas models can. However, your choice may be dictated by what type of unit you are replacing. Often, changing from one energy source to another can be prohibitively expensive.
The cold water supply line connects to the water heater, typically on top of the appliance. Instead of dumping the water on top of the hot water in the tank, a dip tube carries the cold water down to the bottom of the tank. The outbound hot water line takes the water off the top of the tank. That way, when hot water is drawn out, it is at full temperature. Only after most of the hot water has been used do you start to get the hot and cold water mix.
When you open a hot water tap, the water pressure from the cold water supply line pushes the water out of the water heater and refills the tank with cold water. As cold water enters the tank, the thermostat(s) senses the lower temperature and triggers the heating mechanism.
Water heaters have a temperature and pressure relief valve to allow water to escape if the water pressure or temperature exceeds the limits of the tank. Tanks normally operate up to 150 psi. The T & P valve is designed to release water from the tank when the pressure exceeds 150 psi. The valve will also open if the water temperature reaches 210 degrees (F). The T & P valve should have pipes connected to safely carry away the water without flooding or exposing people or pets to scalding hot water.
In the center of the water heater is an anode, sometimes called a sacrificial anode. The purpose of this piece of metal is to corrode instead of the tank corroding. The corrosive action of the hot water attacks the anode, extending the life of the tank. Furthermore, the tank has a bonded layer of glass to further protect it from corrosion.
Water heaters build up sediment as it settles out of the water. This sediment should be periodically drained from the tank to increase the life of the appliance and to improve heating efficiency. A drain valve is located near the bottom of the tank and should be used to drain off the sediment or anytime water must be drained from the tank.
Details Unique to an Electric Water Heater
On an electric heater the thermostats are in contact with the tank, and operate mechanically. The thermostat is like a switch. The switch is on by default, but when the temperature of the tank rises to a certain point, it expands and pushes a small metal rod against a dimpled piece of metal. That movement breaks the contact in the thermostat and stops current from flowing to the heating elements. The upper thermostat also functions as a reset switch and is sometimes referred to as the ECO (Energy Cut Off). Pressing the ECO restores to power to the water heater.
Full size electric water heaters typically have two heating elements, the upper and the lower. Most models are designed for the elements to operate independently, but in some models they may only operate in tandem. When the thermostats are closed, current flows to the immersion heating elements inside the tank.
Details Unique to a Gas Water Heater
The thermostat on a gas heater is an integral part of the gas control valve and is immersed inside the tank. When the temperature drops, the thermostat signals the gas control valve to supply gas to the burner. However, before it allows gas to flow, the thermocouple must signal that the pilot light is lit, otherwise a dangerous gas leak would occur.
The thermocouple is situated in or near the pilot flame. The heat of the flame creates millivolt current which engages a magnet in the gas valve. The gas valve releases gas in a burner adjacent to the pilot flame and is ignited. If the pilot goes out, the current stops and the magnet disengages, preventing the gas valve from opening.
Gas water heaters must be vented to the outdoors. The combustion of natural gas results in toxic carbon monoxide. In the center of the tank is a flew to carry the gases away to the vent mounted on top of the tank. The vent is critical to your safety because it carries the carbon monoxide outside your home.