What is Pipe Freezing?


Pipe freezing is a safe process which isolates sections of piping for repair or alteration. There are two types of processes in pipe freezing, one with uses expendable refrigerant such as liquid nitrogen and liquid carbon dioxide which is sprayed over a section of pipe removing the heat as the refrigerant boils and mechanical pipe freezing using a compressor and recirculation refrigerant in the same manner as household refrigerator. The mechanical pipe freezer has some special components which fasten to the pipes in need of freezing and are hosed back to the compressor. One or two heat exchangers are attached to the section of pipe that is required to be frozen. After an ice plug has been formed repairs may be carried out or the installation of new components such as valves, sinks, pumps.


Pipe freezing reduces the cost of many repairs and save large amounts of energy.


Energy Saving


No need to drain piping of heated water in the heating systems or domestic water piping. These savings range from 15-20 gallons of heated water in a medium size home to hundreds and perhaps thousand of gallons in a large building which has a faulty or no isolation valves. The energy reductions are considered so great that Department of Energy gave a grant to patent # 4,309,875 issued Jan 12, 1982 which led to the development of a mechanical pipe freezer unit which has dominated the U.S. market for over 10 years.


Other Factors to Consider


  1. After a heating system has been drained down many of the convectors need to be bled depending upon the size of the system and location and amount of convectors the refilling of the system may take longer than the drain down and repair.
  2. On domestic water systems with many sinks and showers the faucets may be turned on during the shut down and left open when the water pressure returns causing folding if not noticed.
  3. By freezing a section of the domestic piping there is no need to take out of service all the other plumbing fixtures (sinks, toilets, showers, water fountains) that cannot be isolated from the domestic piping network.
  4. Fire sprinkler have been a problem the standard method when servicing a sprinkler head is to drain the system to test or replace the head causing many extra man hours in labor. The fire department must be notified when the system is off line which can not be accomplished during Norman working hours.




Energy Down the Drain


  • One gallon of #2 fuel oil will produce about 140,000BTU’s
  • One gallon of water has a weight of 8.4 Lbs.
  • Water temperature change in heating system from 55˚F to 180˚F 125˚change
  • To change one pound of water 1˚F will require 1 BTU
  • To change 1 pound of water from 55˚Fto 180˚F requires 125 BTU’s
  • 125 BTU’s per pound x 8.4 per gallon = 1,050 BTU’s per gallon
  • Draining down 1000 gallons of heated water=1,050,000
  • 140,000 BTU’s per oil gallon ÷required energy per gallon of water to 180˚F
  • 7.5 gallon of oil is flushed down the drain with every 1000 gallons of water



Across the United States millions of gallons of heated water is dumped down the drain each day. If only two million gallons is dumped per day that would account for 15,000 gallons of oil being dumped along with the water. After 365 days the amount of oil wasted amounts to fifty four million seven hundred and fifty thousand gallons. The same amount of energy is required to reheat the makeup water after the system is refilled, which brings the total to one hundred and nine million five hundred thousand gallons of oil wasted, and not to forget the wasted water dumped, the energy wasted processing and pumping the water to location, and the vast amount of extra emissions from 109,500,000 gallons of spent fuel into the atmosphere. I am sure that if a study was done the two million gallons of water would be dwarfed by the true amount, making the above number very conservative


Pipe Freezing History and Application


Pipe freezing is the art removing heat (cooling down) from a section of water carrying plumbing pipe at a rate faster than the heat will transfer back from the water on each side of the intended ice plug. If there is water flowing in the pipe it may be impossible to freeze a section of the pipe, the heat removal rate must be greater than the heat conducted to the adjoining sides of the ice plug. With a slow drip the ice plug will be formed but will take more time.


Pipe freezing is by no means a new process. Expendable refrigerants were used back in the 1920’s. Expendable refrigerants, (liquid Co2 and liquid nitrogen) are the most commonly used refrigerants for pipe freezing at this time. By spraying the liquid refrigerant over a section of the pipe heat is removed cooling the pipe at that section and forming an ice plug. In the recent past refrigerants such as R-12, R-22, R-500, R-502 known as Freon (which was the coined name given by the DuPont Chemicals Co) were extensively used for pipe freezing.


The Freon type refrigerants had a chlorine element within their chemical structures. The chlorine within the Freon refrigerants was reportedly destroying ozone in the earths Stratosphere and as a result the EPA started a program to phase out the Freon type refrigerants. The EPA also made it illegal for service technicians to intentional release the refrigerants into the atmosphere and also requiring all personal that work with Freon type refrigerants pass a certification test.


The use of liquid Co2 and liquid nitrogen is still commonly used, Co2 on the smaller pipes 1/4'” to 2.5” and for larger pipes liquid nitrogen which boils at -350˚F and is incorporated in pipe freezing on pipes with diameters over 5 feet.


For smaller pipe freezing applications pipes up to 2.5” self contained pipe freezers units are the most dependable and do not require constant adjustment and monitoring during the pipe freezing process. The self contained pipe freezer is a refrigeration unit that is similar in components to a household refrigerator. What makes the pipe freezer different is the evaporators attach to a pipe. The refrigerant flows into the evaporators were it boils removing heat at temperatures as low as -40˚F cooling the evaporator that is in contact with the pipe bringing the water temperature at that point below freezing forming an ice plug. The ice plug can hold back pressures in excess of 1000 PSI when properly formed.


Quite often when a plumbing repair is required (change faucet washer, repair leak, install new appliances) the supply water must be shut off, if there is no branch valve than the main valve is closed. Many older houses and commercial properties have main water valves that are not able to close and some if closed will not open again. In the main valve is not functioning an ice plug can be formed before and after the valve and a new valve installed with out draining the building or having the town or city locates the street valve and shut it off.


Pipe Freezing Times and Temperatures

Mechanical Pipe Freezer




Pipe Diameter inches Room Temperature ˚ F Approx. Freeze Time Minutes
1/2 70
1/2 80
1/2 90
3/4 70
3/4 80
3/4 90
1 70
1 80
1 90
1-1/4 70
1-1/4 80
1-1/4 90
1-1/2 70
1-1/2 80
1-1/2 90

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