PEX Plumbing Part 3: Couplings and Fittings

Hopefully you will have already read my introductory PEX guide. This guide is intended to go into greater detail of the connectors used to install PEX. For review, common PEX sizes are 3/8″, 1/2″, 3/4″ and 1″. I found for my residential application I used 1/2″ and 3/4″ with only a couple of 3/8″ connectors for direct connections to toilet and faucet.

Couplings: PEX to PEX connection. These are used to continue a run, change sizes, turn tight corners and split off into branches. The first basic coupling is a straight connector. The PEX is attached to both ends with either a regular crimp or “cinch” crimp. (Crimps will be covered in my next guide.) These are also available to change the size of the PEX being used. Picture 1/2″ on one end and 3/4″ on the other. I used this type of reducer to attach my main cold water line to my outside faucets. I did not want to purchase complete new outside faucet assemblies. This type of piece is also available as a “STOP”. One end is completely closed. These are available in brass or plastic, the plastic predominately being used to test pressure. I used the “STOP” pieces in the area where I will eventually be adding a second bath. That way my lines are already in place and if I ever stop playing with this stuff I may get that bathroom done!

Elbows or 90’S: While PEX is flexible and can bend and round corners without difficulty there are times when a 90 degree change is needed. Same principal for connecting as straight couplings.

“Tee’s”: These look just like their name. They are used for dropping a branch off of a line. There are two basic types, ONE, all ends are the same size. TWO, two ends are one size with one larger or smaller. (please see attached photos) The first picture shows a 3/4″ tee. The second shows a couple of variations. 3/4 x 3/4 x 1/2 and 1/2 x 1/2 x 3/4. These are very handy for making branches in your plumbing and/or reducing the size of the branch. Not pictured are the type I used the most, 3/4 x 3/4 x 1/2. I used these to branch off of the main line to a single fixture. Almost like a manifold. (see next guide, to post soon)

Fittings: You also need to be able to connect PEX to faucets, fixtures and existing plumbing. PEX to sweat fittings. These fittings are used to connect PEX to existing copper lines. They are available in a one to one ratio, I.E. 1/2″ PEX to 1/2″ sweat or PEX size with reducing or enlarging sweat connections. MAKE YOUR SWEAT CONNECTION FIRST, AND THEN CONNECT YOUR PEX. This is a 1/2′ PEX, 1/2″ sweat fitting. For an application see my photos. This is a connection to my existing kitchen sink copper. I used this because I did not want to redo the dishwasher connection. PEX to pipe thread connections: These are used when connecting to existing galvanized pipe or directly to fixtures. First, MPT refers to male pipe thread and FIP refers to a female pipe thread. The MPT is threaded on the outside and screws into the female connection. The FIP is threaded on the inside and screws onto the male connection. (I think you get the idea.) They also come in a variety of sizes as needed and you should make your threaded connection first. Swivel fittings: Swivel fittings are the same basic type as pipe thread but allow you to twist on/tighten after the PEX is connected. They are good for connecting to existing fixtures. They come in a brass or a plastic type swivel.

Shut-offs: One of my favorite parts of PEX plumbing. Shut-offs also come in a variety of sizes and styles. At this point you will need to go to the picture link to see the shut-offs and applications. The first picture of the shut-offs shows my hot water connection to the bathroom sink. It has a PEX connection on one end and a 3/8″ male thread connector on the other. This made a standard connection to the sink supply. Please ignore the hole in the wall, I am. Someday I will get around to fixing it but it is under the bathroom sink. This is also where I broke my ribs trying to remove the last of the old galvanized plumbing. Eight weeks later the ribs are better and I am hopefully a bit smarter. The second picture in this set shows a ball type shut-off that I used right off of my water main. Picture three in this set shows the type of shut-off I used in my manifold assembly. These allow me to shut off each branch of my plumbing individually for service or repair. This feature is one of the reasons I have come to love the PEX system. With all of the above you may think that I have covered PEX fittings but I have not included anything about “Push it” or “Shark bite” fittings. Since I have not used these myself I will not go into them here. They tend to be more expensive but eliminate the need for crimping your connections. There is a good amount of information available on the web. You can also find videos of how PEX connections are made. For an important safety issue, please see my guide on electrical grounding.

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