| When heat is applied, the nature and behavior of | | | | The above phenomenon occurs regularly in |
| water tends to change. As water is heated it | | | | high-pressure areas. Many people and even some |
| immediately starts to expand. As long as the service | | | | plumbers are not aware that excessive pressure is |
| pipe between street main and water heater remains | | | | accumulating in their water piping systems, even |
| unobstructed to reverse flow, the water will move, as | | | | though they are protected from the water company |
| it expands, back towards the street main with no | | | | pressure by a regulator. Anytime the water heater |
| measurable increase in pressure. However, should the | | | | ignites, pressure begins to build in the system as water |
| flow in the service line be limited to flow only towards | | | | expands. Simply flushing a toilet, or opening a tap, will |
| the service outlets, by the use of a check valve or | | | | relieve and normalize the pressure until the water |
| pressure regulator, or should a manually operated | | | | heater relights to keep the water at the heater's |
| valve be closed, water, as it expands while heating, | | | | temperature setting. The only way the average |
| cannot escape from the system and a damaging | | | | person knows when this is happening is when the |
| pressure could quickly follow. Water (unlike air) cannot | | | | pressure exceeds 150psi and the water heater T&P |
| be compressed appreciably. | | | | relief valve kicks off. Unfortunately, water pressure |
| The confinement of water results in what is called a | | | | between 80-150psi has a deleterious effect on the |
| "closed system." Water expands at a rate of | | | | entire plumbing system and causes rapid and |
| approximately 0.00023 pct. for each degree of | | | | unnecessary wear on all its components. To solve this |
| temperature rise. If all of the water in a 30 gallon water | | | | problem it is necessary to install a heat expansion tank |
| heater were raised from 60 to 140 F, a temperature | | | | at the water heater, which will absorb the expanded |
| rise of 80 degrees, it would increase the original | | | | water and keep the pressure at a normal setting. A |
| volume to 30.55 gallons, an increase of.55 gallons. | | | | simple test is required to determine if this condition |
| Water confined in a storage tank or piping system will, | | | | exists. |
| when subjected to a temperature rise of 10 degrees | | | | We recommend that anyone living in a high-pressure |
| (increasing from 75 to 85 degrees) increases pressure | | | | area implement the test and make the necessary |
| from 50-250psi. | | | | correction. |