Fuel for Thought

How To Prevent Oil Line Freezing in Frigid Temperatures

Posted by Robert LaFlamme on Mon, Feb 04, 2013

frozen oil in filterWe had a prolonged cold snap last week which caused a few customers with tanks that are outside of their home or in an unheated space to lose their heat.  The reason for this in most cases was that the oil in their oil lines had gelled or waxed.   This happens because heating oil will start to cloud at temperatures below 32 degrees Farenheit.  Clouding is the early stages of gelling or waxing when oil begins to cool.  When oil gets cold enough it will reach its pour point, the point at which it will no longer flow.

What is happening to the oil at low temperatures is that wax crystals begin to form.  In extreme cold weather like we saw last week they will form long hydrocarbon chains that can clog an oil line.  And it is at the narrowest point in your oil supply system such as your oil line, oil filter, or oil valve where the supply disruption will occur.

Solutions to Prevent Oil Line Freezing

Adding a Fuel Oil Treatment

To help prevent the oil from waxing our company adds a quart of Fuel Oil Treatment which our customers will see on their bill listed as FOT.  We have over the years used additives from  two different companies with excellent results.  These companies have a patented product so how they work to reduce the temperature at which oil will cloud and pour is not clear.  We have learned that most work by matching the alkanes or wax crystals in the fuel preventing them from forming the long chains that can stop the flow of oil in an oil line.

Oil Lines on Top of the Tank

There are other factors that can cause problems for someone who stores oil in an outside or unheated space.  The most common one is having water in the tank which is not an uncommon thing due to the constant change in heat and humidity around the tank which causes condensation inside the tank.  We have seen people with tanks in freezing temperatures with oil lines that supply off the bottom of the tank have water build up and freeze completely stopping the flow of oil or water. 

This situation is corrected by supplying oil from tanks in freezing temperatures from the top of the tank with the oil line extending into the tank to within 3 inches of the bottom (well above the level of any water that might accumulate).  The State Fire Marshal's Code also requires that tanks in unheated spaces have supply piping that comes off the top of the tank.


One option that people with outside oil tanks have is to use kerosene instead of heating oil.  Kerosene has a much lower cloud and pour point and will store at colder temperatures without problem or needing an anti-gel additive.  We stopped selling kerosene over 15 years ago when it became so expensive and most of our customers with outside tanks switched to using cheaper heating oil with the Fuel Oil Treatment.  The reason that kerosene is so expensive is that it is also used as jet fuel and there has been a major increase in the number of people flying over these past 30 years.

Other actions that you can take to protect your oil line from gelling is to wrap it in heat tape or insulation, or both.  We use a larger diameter oil line when we install a tank that will be subject to freezing which helps prevent clogging.  Most oil lines are 3/8 inch in diameter, we use a 1/2 inch line and valves.

Using a Single Pipe Oil Line

It is also a good idea to use only a single pipe oil line coming from an oil tank that stores oil outside as opposed to a two pipe system.  The advantages of a two pipe system is that it keeps a flow of oil going through the pipes and returns oil that the burner didn't use back to the oil tank and with the unused oil any air that might have gotten into the oil.  If you have ever lost your heat because your oil pump lost its prime due to pulling in too much air you would be inclined to think that a two pipe system is a good solution.  The problem with constantly flowing oil through your burner is that it is always cold oil, and your burner runs best with warm oil.  With a one pipe system the oil has a chance to come into the burner compartment and warm up before being delivered by the pump to be sprayed by the nozzle into your heat exchanger.

I hope that you find this information helpful if you have a tank that stores oil in a place that is subject to freezing temperatures and that it helps you to prevent having the oil in your tank wax or gel.

© Crowley Fuel Co., - Contact Us for Heating-Related Emergencies


Tags: Heating Oil Company, Oil Heating