There are 3 main factors which contribute to freezing of a water service lateral – Frost Depth, Water Usage, and Exposure to Weather.
A. Frost Depth - “Normal” maximum frost depths in our region are 4 to 6 feet. In paved areas or other areas where snow is removed frost can drive down deeper. As the frost level goes down it approaches and, in extremely cold winters, can reach near the depth of water service laterals. In older parts of the Utility’s service area water mains and service laterals may only be between 6 and 7 feet deep. In areas of newer construction water mains and service laterals should be 7 feet deep or more. Think of frost as simply a block of ice in the ground which grows larger and larger from the ground surface downward. If the block of ice touches or surrounds a water service lateral, the lateral will freeze without water running through it. Frost depth is the most important factor in causing water service laterals to freeze underground.
B. Water Usage – This applies to both the water mains and the water service lateral itself. Lower usage is going to mean the water stays in the pipes longer. If water usage in the mains is lower the water gets colder. If water usage on a lateral is very low or even stops (such as when a resident goes on vacation) the water in the lateral will become even colder and, if the frost is deep enough, the lateral freezes. Customers with low usage (single occupant homes for example), businesses with long periods of no water usage on weekends, homes unoccupied during vacation periods, etc., are going to be much more likely to freeze during these cold weather periods.
C. Exposure to Weather – There are 2 ways municipal water supply temperature can be affected by the air temperature. Your service lateral may be exposed to drafts or cold air near where it enters your building. The other “exposure” is from water being stored in elevated water towers where it cools (or warms) during the time it stays in the tank. Most water towers in our region will develop ice along the tank walls during a winter season, but the majority of water remains liquid due to the daily filling and usage cycle.
There are a number of water service laterals which are known to routinely freeze each year. Some of those freeze on the customer’s portion of the water service lateral and some on the Utility’s portion of the lateral. The Utility is required to annually notify those customers whose service laterals freeze on their portion to either take measures to prevent freezing or, at their option, pay for thawing the service lateral if it freezes. If the freezing is something known to occur on the Utility portion of the water service lateral, the Utility either takes measures to prevent freezing or takes care of any costs to prevent freezing. You may also wish to review the PSC’s FAQ on this topic.