Flare fittings are a type of pipe and tube connection used for liquids and gases. Flare fittings are unique in that the fittings are beveled or flared to prevent a leak-tight seal. Flare fittings copper tubing is commonly used for heating and cooling applications such as heating oil in a furnace or refrigerant in an AC unit. Flare fittings are also used in flexible connection hoses such as natural gas ranges and dryers. Understanding flare fittings and there uses will benefit you in your next DIY project or remodel.
(1) When to Use a Flare Fitting
Flare fittings are used to create leak tight connections by using pipe deformation to achieve a leak tight seal. Similar to compression fittings, tubing is deformed by flaring or opening the end of the tube to create a male-female union that seals when connected. Flare fittings are used over compression fittings when mechanical pullout of the fitting is a concern under operating pressure.
Most potable water connections will not use a flare fitting to connect but other systems such as heating oil connections of AC cooling lines will use flare fittings to connect copper tubing to pumps and valves. Natural gas also uses a flexible gas connectors with flared joints to connect to
(2) What Are The Flare Fitting Types
There are three major types of flare fittings: SAE 45° flare fittings, JIC 37° flare fittings, and AN 37° flare fittings. JIC 37° and AN 37° flare fittings are commonly used with hydraulic lines in automotive or aerospace applications. The most common flare fitting found and used in plumbing is the SAE 45° flare which will be listed as a flare fitting. All flare fittings come as a male flare and female flare with a connecting flare nut or or preformed connector, such as the flexible gas connector hoses.
(3) What Are the Flare Sizes
Flare fittings are sized by nominal outside diameter (OD). Typical flare fitting sizes are 1/4″, 3/8″, 1/2″, 5/8″, 3/4″, and 7/8″ in North America. Flare fittings that connect into standard pipe threads will be sized with both flare and pipe thread size. Pipe threads are sized from the inside diameter so a pipe thread connection will be larger than the nominally sized flare connection.
(4) How to tell if it is a Flare Fitting
Flare fittings are easy to recognize by the beveled face. Compression fittings and pipe thread fittings will not have the beveled edge. Compression fittings are measured from outside diameter of the pipe or tube so will have a similar nominal size to flare fittings.
To recognize what type of flare fitting that you have, most flares for residential use will be the SAE 45° flare which is commonly found in retail stores. The JIC 37° and AN 37° flare fittings are typically used in high pressure hydraulic lines and will have an additional sleeve on the female flare end that sits underneath the nut. There are tools that can be used to tell the angle of the flare and assist in identification.
(5) Should I Use Pipe Joint Compound or Pipe Thread Tape?
No, flare fittings do not require joint compound or thread sealant to create a sealed fit. Flare fittings are designed like compression fittings to use soft tubing or pipes that deform to create a seal. In flare fittings, soft copper tubing is flared to create a seal between the male beveled edge and the female nut, creating a leak tight seal. Pipe tape or joint compound can interfere with the male flare connecting with the female flare as the thread sealant prevents full tightening of the union.
(6) What Materials are Flare Fittings made of?
Flare fittings like most indoor plumbing fittings are made of lead free brass. Brass is used as it is durable, corrosion-resistant, and easy to manufacture. All brass fittings that are used for potable water systems need to be lead free. Fittings will usually state the type of brass and lead content on the product packaging. For drinking water, lead content is important and specified by law to be up to 0.25% of the wetted surface area content per the Reduction of Lead in Drinking Water Act.
(7) What Pipe or Tube Materials Work With Flare Fittings
Soft material tubing such as copper tubing, aluminum tubing, or steel tubing that can be flared will work. For most plumbing systems, copper tubing will be used as it is readily available. For hydraulic lines, aluminum or steel tubing might be required due to the higher pressure demands of the system. Plastic tubing, rubber tubing, or other synthetic tubing are not be used with flare fittings.
(8) Are Flare Fittings Dangerous?
Flare fittings are not any more dangerous than other types of plumbing fittings. Flare fittings are designed to be used with proper flared tubing or pipe. Ensuring properly a properly flared connection and testing the connection prior to turning on the flow of liquid or gas is important. If in doubt, reach out to a licensed plumber in your area for help in making the connection.
As to the question of reproductive harm, flare fittings are not any more harmful than other type of fittings. The Reduction of Lead in Drinking Water Act is the federal standard for the level of permissible lead in plumbing fixtures for potable water. The allowable lead content in products for potable water changes from up to 8% to an average content of less than 0.25%.
(9) Are Flare Fittings Expensive?
Flare fittings are not more expensive than other types of plumbing fittings such as compression fittings and some fittings may be more or less expensive. Flare connections do require additional tools such as clamps, flaring tool, and tube benders and take more time to form and connect.
(10) Is Flaring the same as Swaging?
No, flaring is not the same as swaging. Flaring is the process of expanding a tube end or pipe end by creating a beveled opening, similar to a trumpet. Fittings pieces such as flare nut are necessary to complete the joint. Swaging is the process of expanding a tube or pipe to accept a same-sized pipe. Copper pipes for drinking water may be swaged to create a hub and plain end connection but cannot be used for other applications. Swaged pipes are solder together where flared pipes are attached together.
Conclusion
As a homeowner, flare fittings may be a necessary part of your plumbing system. Most flare fittings will be found in connections to natural gas or AC units, and less commonly in heating oil units. For more information, take a look at our other articles for more kitchen and bath tips.