Imagine if you are watering the lawn and you have one of those connected bottles of your favorite fertilizer. Now imagine that you have just finished working. There is still water and chemical in the hose. In the old days there would have been the propensity for this concoction to drain back down into the water. Since this was a problem in the past, water companies have installed check valves, usually located at the meter. This keeps our contaminants and the contaminants of our neighbors from entering the water supply and causing problems.
Thermal expansion of water in a closed plumbing system can create a number of annoying and potentially dangerous problems. These include: the buildup of unusually high pressure in a system (even when a pressure reducing valve is installed); pressure surges; and the chronic or continuous dripping of a temperature and pressure (T&P) relief valve. In addition, dripping faucets and leaking toilet tank ball cock fill valves are also symptomatic of thermal expansion.
More serious problems can also occur due to thermal expansion. When dangerous pressures are built up in a water heater, internal parts may fail such as the internal flues, fittings or water connections. If a flue way collapses it can lead to the potential release of toxic gases, such as carbon monoxide into your home or office. Thermal expansion can also lead to a ruptured or distorted hot water heating tank and may void the warranty.
The solution is for an expansion tank to be installed when a new hot water heater is installed. Unfortunately, this is one of the shortcuts taken when someone other than a licensed plumber installs the hot water heater for you. It can create a very dangerous situation. If left undone:
- It could lead to a rupture or explosion at the worst
- When water is heated it expands. Water expands when heated therefore, the additional volume of fluid created has to go someplace.
When an expansion tank is installed the excess water enters the pre-pressurized tank As the temperature and pressure reaches its maximum, the diaphragm flexes against an air cushion (air is compressible) to allow for increased water expansion. When the system is opened again or the water cools, the water leaves the tank and returns to the system. This is a surefire way to make sure you systems are safe and are according to code.