When Vermont's weather becomes severely cold, PACIF members contact Loss Control asking about the safest ways to thaw underground water service lines. This is an important consideration because incautious thawing can cause extensive damage to property — and also, in the worst cases, to people. As desirable as it is for the municipality to meet its obligations and respond to citizen water service problems promptly, it's also important to use safe methods and avoid causing any adverse consequences.
We Advise Against:
Applying low voltage and high amperage to the frozen line with an electrical device such as an arc welder or a "Hot Shot". This method of electrical resistance (or simply "electrical") thawing makes use of the electrical conductivity of the pipes, and although it can be effective in completely known systems, it can cause electrical shorts, fire, and/or melting when unknown ground wires, service lines, or other systems (such as domestic plumbing) are involved. Improper electrical thawing has resulted in so much damage — whether to parts of structures or causing total fire losses — that most arc-welder manufacturers now recommend against using their equipment for this purpose.
Allowing municipal staff to perform any work on non-municipal water lines. These are the responsibility of a homeowner or business owner, and even well-meaning assistance can make the municipality liable if damage occurs.
Hiring a qualified third party. Transferring the risk to a properly licensed and insured plumbing contractor is the best way to protect property and municipal employees. The municipality can hire these contractors on its own behalf or recommend them to citizens who have frozen lines on their property. In either case, it is critical that the municipality use or refer only contractors for whom it has on file a Certificate of Insurance (COI) confirming that the contractor has current statutory workers' compensation coverage and general liability coverage with limits of $1M per occurrence and $2M aggregate, as a minimum. If the work will be for the municipality, the COI should also name the municipality as an additional insured.
Pumping warm water into the service line with flexible tubing that inches forward as the ice melts. This method is effective, but it can take some time, and existing plumbing elbows and fittings can prevent the tubing from being inserted fully.
- For small service lines, push a ﬂexible half-inch or smaller plastic tube into the frozen pipe while pumping warm water into the tube. The water pressure can be obtained directly from a nearby building or through the plumbing system. A hand pump ﬁlled with warm water can also be used if connected where the meter is temporarily removed from the service line.
- For large service lines, this is best accomplished with a water jetter connected to a hot water supply. Portable, self-contained devices on the market (such as the MagiKist pulse-jet de-icer) will heat and recycle a tankful of water and require only one person to operate safely. In some cases, a two-person team can set up and use a hot water source with a jetter or pump, garden hosing, food-grade tubing, and about $30 worth of "T" fittings. The manual approach requires more care in containing and cleaning up water spills to prevent incidental damage.
Thawing from the outside of the pipe if its exterior is exposed.
- This method is not recommended for plastic pipes which could melt or be damaged by heat.
- Do not thaw the center of the frozen spot, for this can make an ice pocket where the trapped water can boil and cause the pipe to explode.
- In meter pits that are too small for a human to enter, vehicle exhaust can be directed in with an attached hose, and the heat will thaw the meter within a few minutes. Workers must work in pairs and take care to prevent carbon monoxide exposure.
- Use a portable heater, steam cleaner, or a heat cord to warm the pipe.
Using "frost bottom" water meters. These are designed so the bottom will freeze and pop off before the line freezes, thus allowing water to drain from the line.
If you have questions or would like more information, please email us at: email@example.com or call 800-649-7915.