Sometimes it can be the simplest job, such as changing a tap washer. At other times, it can be something slightly more complex, perhaps changing a radiator valve. Whatever the task, the thought of having to mess around trying to turn off a seized mains stopcock or drain down a central heating system, can initiate a certain amount of procrastination.
At other times, an urgency such as the repair of a burst pipe might be frustrated by the inability to locate either the domestic or the water provider’s main stopcock.
Whichever, the process of freezing and creating a plug of water in the supply pipework to temporarily interrupt the flow can be a quick and efficient method of facilitating a plumbing procedure.
Using a pipe freezing process is ideal for cutting the water supply in the immediate area to allow for the plumbing of T-pieces for appliances, radiator valve changes, pump and zone valve replacements. It can even facilitate the repair or replacement of a seized mains stopcock.
Pipe freezing can be accomplished by using refrigerants provided by disposable aerosol canisters or by specialised, electrically operated portable machines.
Aerosol canisters are designed to operate in conjunction with a dedicated kit. This kit comprises of thermal sleeves that wrap around pipework and valve connector attachments with refrigerant delivery tubes. These sleeves are usually made of durable nylon material.
Thermal sleeves come in a variety of sizes to fit the common pipe diameters in use today. The thermal sleeves act as a barrier to contain the evaporate and to delay thawing.
The refrigerant is a volatile gas that has been compressed to form a liquid and then held in that state under pressure in the canister. It is the sudden reduction of pressure that enables the liquid to return to its gaseous form. In doing do, it draws heat from its surroundings. This causes the freezing action.
For plumbing purposes, the thermal sleeves are applied to pipes and the liquid gas introduced where it evaporates to form an ice plug close to the working area, and if necessary, at a point beyond to prevent backflow. There should be a distance of at least 200 mm between the working area and the sleeve (s).
The process works best on horizontal pipework, but can be used on a vertical pipe.
There must be no flow of water through the pipes at the time of freezing, as this would inhibit the formation of an ice plug. Boilers and pumps must be turned off and leaks temporarily patched. The water in the pipes must also be cold, with the ambient room temperature below 20 degrees C for optimum efficiency.
One end of the flow pipe for the refrigerant is attached to the thermal sleeves, which in turn must be securely fastened to the plumbing pipework. The other end of the flow pipe is attached to a valve located on the canister. By operating the valve, the liquid under pressure in the canister passes down the tube into the thermal sleeve, where it expands and converts into a gas. This causes water in the plumbing pipe to freeze and form an obstructing plug of ice. The obstruction blocks the water flow. The refrigerant should be delivered in short bursts to prevent wastage or overspill. The thermal sleeves must remain in place until the plumbing work is completed. A naked flame and blowtorch cannot be used and plumbing fittings that are to be installed must be of compression or other non-heat requiring types.
Depending on the pipe-work material and diameter, and the ambient temperature of the water and room, the plug will form in copper pipes in around five minutes. Plastic pipes will take up to twenty minutes. An audible click from the device will inform the user that the plug has formed and that the plumbing work can commence. The ice plug will effectively prevent water flowing for about thirty minutes although it is possible to maintain the plug with further bursts of refrigerant.
It is important to ensure that there is sufficient aerosol refrigerant to complete and prolong the plumbing if it becomes necessary. The aerosol and gases produced must be used in a well-ventilated area. The refrigerant will cause serious burns if it comes into contact with skin or eyes and must not be inhaled.
Pipe freezing machines are an alternative to using a disposable canister. The principal of freezing the pipes is similar, however, the gas evaporation and re-pressurising is contained within the machine and is much safer to use. It is also environmentally friendly as no toxic gases are released into the atmosphere.
The machines are electrically operated and will supply and maintain a freezing process to pipes indefinitely, so long as the power supply is maintained.
The refrigerant is delivered via pipes to clamps attached to the pipework. The freezing process and maintenance are automatically controlled by the machine, which will also indicate when the ice plug has been formed. The clamps and the freezing process must remain in place until the work is completed.
There is a variety of machines on the market and manufacturers make machines that are capable of freezing any diameter of a pipe. The larger machines are regularly used by water companies to complete major pipe maintenance work.
Pipe freezing machines are expensive to purchase but can be hired on a daily basis from plant and tool hire companies. Currently, expect to pay around £50/day.
Both methods of freezing pipes for plumbing purposes are very effective if the manufacturer’s instructions are followed. Occasionally, where pipes are located in confined spaces, or very close to walls, neither conventional sleeves nor clamps can be effectively used. With pipe freezing machines there is a type of clamp that is held in place by rubber straps. The clamp freezes one side of the pipe and will take longer to form an ice plug. However, this can be used effectively where a normal clamp may not fit.
When cutting pipes to facilitate plumbing work, consider implications surrounding earth-bonding issues with electrical supplies.
For a one-off job, pipe freezing aerosols, and the kits that are available to facilitate their use may be the most practical option. Inclusive kits vary in price depending on size and the required application. A very simple kit can be purchased for around £30. Fittings and gas canisters can also be purchased individually. The kits and accessories are widely available from plumber’s suppliers and DIY outlets.