How to solder copper pipe

Learning how to solder copper can really save you money if you're planning to fit copper pipework for a full sanitary installation. On the other hand, if you only have two or three fittings to install for a shower or tap, if you don't have the right tools or if you just don't have the patience for plumbing, it's best to use compression fittings or even push fit fittings instead. The advantages of these fittings is that they are easy to install and reasonably priced (compression fittings being the least expensive of the two options). Alternatively, PEX pipe can be used in place of copper pipe but this will cost you much more. All in all, the most cost-effective solution is to use copper.

Steps

1. Tips for soldering copper

2. Prepare to solder the copper pipe

3. Choose your flux and filler metal

4. Braze or solder the copper fitting

5. Cleaning a copper joint

Below you'll find a video setting out the main steps to follow to successfully solder copper pipe.

1. Tips for soldering copper

In practice, heating copper is fairly easy. However, bear in mind that applying excessively high temperatures will make the material porous and possibly lead to leaks. Bear in mind that the most important factor to control when soldering copper pipe and fittings is temperature. In simple terms, you should never allow the copper to go past the point where it turns dark red in colour.

The success of your soldered or brazed joints also depends on the quality of the copper. Cheap copper is often too high in carbon. When heat is applied to this type of copper, the flame will burn the carbon leaving behind microscopic holes which will make your pipework porous.

Copper pipe or tube cannot be butt welded like steel or stainless steel. Instead, it must be joined with the addition of a special fitting used to connect two sections of pipe. These fittings are very thin which makes them easy to fit and improves the look of your finished installation. Known as end feed, or capillary, fittings, they are designed to slot over tube sections leaving a small gap called the capillary space where filler metal is inserted to secure the connection.

This type of joint is called a capillary joint. While the terms 'soldering' and 'brazing may be used interchangeably – even by professional plumbers – they aren't exactly the same thing. Copper soldering takes place at temperatures of below 450°C while brazing requires minimum temperatures of 450°C and provides a much stronger connection.

Different types of copper pipe fittings

A wide range of different copper end feed fittings is available so you are sure to find the appropriate fitting for any kind of installation layout. By combining different types of fitting, it is possible to cater to any pipework layout. It is even possible to find tap connectors with a soldered copper connection on one side and a threaded brass connection on the other for connecting flexi hoses.

Copper is a metal that readily oxidises. The advantage of this is that it allows copper to protect itself. Once the copper has oxidised, the grey-green coating works as a protective layer around the metal to prevent further corrosion. The best example of this natural process is the copper dome roofs of some old public buildings which have turned green over time as they have oxidised.

In order to install a copper fitting, you must first carefully clean the surfaces that will be in contact with the filler metal. This means the end of the copper pipe section and the inside of the capillary fitting. There are a few ways to do so but the most effective is as follows:

• deburr the end of the copper pipe;

• remove oxidation from the copper pipe using wire wool or emery cloth;

• finish off with some burning alcohol.

Flux is used to facilitate the bind between the copper and filler metal. It can come as a liquid, paste or powder or it can be included as a coating on brazing rods. Flux is required to meet standard DIN 8511 which governs the requirements for fluxes used for brazing.

Your choice of flux depends on the type of installation you are dealing with. You must use the right type of filler metal depending on the type of soldering you are doing (i.e. soft or hard). Standard ISO 3677 (2016) specifies designations for filler materials for soldering and brazing, on the basis of their chemical composition. When it comes to gas, oxy-acetylene will provide the best results for brazing.

* The specification AWS A5.8/A5.8M: 2011 sets out the requirements for the classification of brazing filler metals. These classifications provide details about the characteristics and usability of a filler metal.

Each type of soldering or brazing requires a specific type of flux (or flux coated rod) before any filler metal is added.

Soft soldering

Soft soldering (under 450°C) can only be used to join cold water pipes. It is important to tin the end of the pipe and the female part of the fitting before soldering. Tinning consists in applying a thin layer of solder to the surfaces that will come into contact with each other to ensure a good connection. If you fail to prepare your surfaces adequately before soldering, your soft solder joint won't last.

Brazing / hard soldering

When hard soldering, or brazing, at temperatures of 700 to 750°C it is important to apply heat gradually. Be careful – overheated copper will become porous. As soon as the right temperature is reached (the copper should be dark red in colour) the filler metal can be applied in the capillary space. As the solder melts, the filler metal runs into the pre-fluxed joint.

The copper-phosphorus, brass or brazing alloy used as filler metal goes from a solid to a liquid before quickly turning back into a solid again. The most important skill when installing any plumbing or heating system involves controlling the heat as the solder melts.

When installing a copper/brass fitting it is important to bring the brass part to the filler metal melting temperature first while gradually bringing the copper up to temperature. Copper is much thinner than brass and boasts excellent thermal conductivity meaning it will heat up much faster. If you are installing a tap connector, be sure to remove the inner seals first to prevent damage.

Please note:

• Rigid copper fittings anneal and soften as they are heated.

• Be sure to prepare adequate support to avoid weakening your installation.

After brushing the joint, you can remove any black marks using a diluted sulphuric acid solution. Rinse the joint thoroughly afterwards to remove all traces of acid. Always take great care to prepare for any accidents when soldering or brazing. Your work station must be well ventilated and free of clutter.

It is essential to wear a welding helmet and gloves, as well as appropriate work clothes, when performing these tasks.

• You will need two pairs of protective gloves: one pair for soldering and another for applying the sulphuric acid solution.

• Safety glasses with lateral protection are required to protect the worker from projections.

• A fire extinguisher should also be on hand no matter the situation and it is best to use a gas lighter rather than an ordinary lighter.

Required skills

As long as you are meticulous and follow the key recommendations closely, you should be able to solder copper pipe systems yourself for a reasonable cost. With a bit of practice, the skills required should be attainable for most DIYers.

Time required

5 mins per soldered/brazed joint

Number of people required

1 person

Tools and equipment

• Soldering iron (soft soldering) or oxyacetylene torch (brazing)

• Solder or filler metal

• Steel scrubber

• Diluted sulphuric acid solution

• Burning alcohol

• Deburring tool

• Copper pipe fittings

• Flux

Safety and workwear

• Safety goggles

• Face mask

• Work clothes

• Welding apron

• Welding gloves

• Safety shoes

• Flame protection depending on work environment

Please note: this is a non-exhaustive list; be sure to match your personal protective equipment to the job at hand.

• PEX pipe buying guide

• Brass pipe fittings buying guide

• PE pipe buying guide

• How to use a compression fitting

• How to fit PE pipe fittings