Pipe Joining Methods – Water Piping



 How To Put Water Piping Together

In the next few paragraphs, we will go over the different ways we, as plumbers join pipe and fittings together. In each description, we will list the different plumbing systems and which joining methods apply, and finally, the benefits and drawbacks of each.

Soldered Joints – This is the process of joining pipe by melting a filler metal with a low melting point into a joint. When the filler metal cools it bonds the two pieces of metal together. In plumbing, this technique is mostly done with copper piping. Soldering is used on all three plumbing systems water, waste and vent piping. 


  • The science behind soldering is very old and has literally stood the test of time. 
  • There is a learning curve but it isn’t steep by any stretch so it’s fairly easy to learn.
  • The joints are fairly strong and water tight if done properly.


  • On larger diameter copper piping (3″ and up) there is quite a bit of room for human error. Has the piping been cleaned properly (using flux)? Does the person doing the installation have enough experience using heat or torch control to heat the joint properly and uniformly? Capillary action draws the filler metal into the joint, if the bottom of the joint gets too hot you can draw the solder down to the bottom of the joint leaving a gap at the top.
  • The piping materials and filler metal are expensive. With owners, installers, and consumers being so cost-conscious these days copper can be cost-prohibitive.
  • If proper heat or torch control is not observed the hard copper can be annealed (softened) if too much heat is applied.

Brazing – Brazing is very similar to soldered joints in that a filler metal with a melting point lower than the metal being joined is used to fill a joint between two base metals. Brazing is done primarily on water piping and more specifically on water services or larger diameter piping. It is a much more forgiving technique.


  • As with soldering the technology is mature.
  • The joints end up being stronger than the filler metal because of the way it reacts to the metal being brazed and are significantly stronger than a soldered joint.


  • Most of the same drawbacks that you’ll find with soldering you’ll see here as well.
  • One big drawback with brazing is that you have to get the pipe and fitting very hot for the filler to melt and be pulled into the joint. You end up annealing the copper making it soft. On large diameter copper, you run the risk of future pipe and fittings failure.

Threaded Fittings – Threaded pipe and fittings as they relate to galvanized water piping is a dying joining option. It will always be used for repairs or on specialized fittings i.e, flange fittings but it is not a preferred installation.


We can’t think of a single realistic benefit of installing galvanized pipe and fittings.


There are many drawbacks to using threaded fittings one of which is the fact that galvanized pipe and fittings can be difficult to repair. As galvanized pipe and fittings start to break down, sediment and rust begins to build up inside the piping shrinking the inside diameter of the piping. If a repair needs to be done, many times the plumbing professional chases down more damaged piping than originally expected. To make a repair on threaded pipe and fittings the plumbing contractor needs to have the equipment to cut and thread the pipe, if the equipment isn’t available the plumbing technician has to have the skill set to be able to make the correct measurements. Those measurements have to be related to a wholesaler with the capability to cut and thread the piping. If the measurements are incorrect that could affect the entire shutdown of a building which is time, money and one very upset customer.

If the system is aging it’s not unusual for the threaded fittings to be fused and extremely difficult to remove. This usually involves cutting the piping in the general area of repair and finding a fitting that the piping can be backed out of or cutting the piping close to the fitting and caping the remaining pipe. (Please see Caping Out Threaded Pipe or Nipples). 

Fuse Seal – (Polypropylene piping) Although this technology has been around since the 60s it’s had an extremely tough time gaining widespread use. Fusion technology is used when the plastics being joined can’t be joined using cement. The basic procedure is as follows, a device/tool is used to heat the fitting and piping to a certain temperature melting a thin layer of the polypropylene plastic, the pipe is inserted into the fitting making sure the pipe hits home. After a certain time, usually around 15 to 20 seconds the pipe and fitting can no longer be manipulated and the fitting cures. The pipe and fittings actually fuse into one piece along the area of contact ensuring a positive seal.


20% material savings versus copper. 


There is a learning curve with the preparation and joining process however it is far more forgiving than it’s copper counterpart. You will realize a labor savings once the technicians become proficient at the joining method.

It is naturally acid resistant so neither hard water nor soft water has any affect.

It has little expansion or contraction. No worries with freezing and thawing or pouring in a concrete deck.

It is not an efficient conductor of hot or cold temperatures therefore there is very little condensation or sweating.

Aqua Therm polypropylene gives you a 10 year (yes 10 years) insurance policy against product failure or incidental breakage. You can drop something on it and if it breaks it’s covered.

Some of the new materials being offered are green in the way the pipe and fittings are joined and in the material itself.

There is zero electrolysis and a negligible amount of electrical conductivity.


Even though the product and joining method are mature it is still considered an “off” choice here in the US. 

Although a large percentage of plumbing technicians have handled the material at some point in their careers it is not typically used day to day so it has never become second nature on the installation. (We’re not saying no one is an expert just very few.)

Traditionally the fittings are not full port however Aqua Therm does make full flow potable water fittings.

This is debatable but some would say you have to use double the pipe hangers to make up for the lack of rigidity.

Over 4″ I.D. piping must be mechanical joint. 

Mechanical Joint – A mechanical joint is any method joining piping or fittings by way of a coupling that uses compression of a rubber gasket to ensure a water tight seal. Two examples of mechanical joints are flanged pipe and fittings, grooved pipe with couplings or fittings that have a rubber gasket which sits inside the groove and the rubber is compressed filling the groove and sealing the joint.


In theory the repairs on these applications are easier to perform. 

These are high pressure fittings so their tolerances are high. You can install very large diameter pipe and fittings.


It takes a fairly high skill level to prepare and install this pipe and the accompanying fittings. It is easy to install the mechanical fittings for grooved pipe but the measuring and grooving of the pipe takes some know how. With regards to flanged pipe, spool pieces and flanged fittings you have to have a very high skill level to perform new installations or repair. To be able to measure correctly, remove the old, replace with new takes some skill especially with large diameter pipe and fittings. It very hard to move 8″, 10″, 12″ pipe a half an inch because you blew a measurement.

Fittings are heavy, bulky, and expensive. 

Repairs are labor intense

Although you can use plastic pipe with mechanical fittings, the skill level to install is no different but you may get a break in material costs. 

Add your comment

Related News