How To – Using A Union To Connect Copper And CPVC Water Line

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    Most homes built in the past 10 years use CPVC feed lines for the water supply but many homes may have a mixture of copper and CPVC depending on the appliance or fixture that is being plumbed.

    You are likely to see these transitions between the two different materials at your water meter, outside hose bibs, water heaters and even toilets and faucet feeds.

    When making the transition you have two basic choices. You can install a shutoff valve that has a CPVC glue side and a copper sweat side  or a compression fitting on the copper side of the valve that will give you the ability to turn off the connection and make a disconnect if repairs are needed. The second type of connection is a union.

    A Union Connection does allow a disconnect at the transition point but primarily this type of connection is used in areas where the connection is considered permanent.

    Installing Your Union

    The first thing you will notice when you go to your plumbing supply house to purchase a transition union is that there are two types of connections for the copper side of the connector.  Normally if you are placing the union in an area where servicing is a consideration you can opt to use a compression type fitting. Such a connection would be for your toilet or for a sink supply line.

    If you are installing the union inside the wall for a shower or if you are making the connection for an outside hose bib or water meter you want to use a soldered connection.  If the soldering is performed correctly it will provide a better and longer lasting connection that can not be loosened by vibration of a pump or movement due to servicing of an appliance.

    Once you have selected the proper size and type of fitting you can begin by disassembling the fitting.

    It is very important that you disassemble the union before soldering the connection. Inside of the union there is a rubber washer and the CPVC end of the connector can also melt. NEVER SOLDER A UNION WITH THE RUBBER WASHER STILL INSTALLED. You will definitely ruin the connector and either end up buying a second one just to get the CPVC side or be forced to start all over again.

    If you are use to soldering copper pipe you will find that the brass connector takes a bit more heat to get the solder flowing. It is very important to clean the fitting and the end of the pipe and you must use flux to promote good solder flow.

    Once the copper pipe has been fitted with the brass side of the Union you can attach the rest of the pieces including the rubber washer and CPVC nib before gluing the CPVC nib to your pipe.

    I suggest that you completely assemble the fitting because although CPVC and copper pipe can be nudged into position it can be difficult to thread the two ends after they are permanently attached to the pipe.

    Prepare the CPVC ends as you normally would with primer and then glue. Hold in place for at least a minute until the glue sets up.

    The YouRepair Store carries a full line of Plumbing Tools and Materials to complete your next job.

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