How To Solder Copper Pipe

In our many articles on Solar Water Heating we have frequently mentioned copper pipe, but never how to solder it to make water-tight connections. In this article we will show you how to solder copper pipe safely and reliably. It is actually very easy as long as you are careful and take your time.

Soldering copper pipe end feed joints

Soldering Copper Pipe

In most solar collectors 10mm or 15mm annealed copper pipe is perfect. It is the pipe used most commonly in domestic plumbing and so it, and the related fittings are the most competitively priced.

In order to to make a joint between two pieces of copper pipe you need the following:
* Copper pipe (annealed).
* End feed joint.
* Wire wool or emery cloth – used to remove dirt and grease from the ends of the copper pipe.
* Rosin flux – a paste which stops the copper pipe from oxidising and helps the solder to flow.
* Solder (lead free) and a blow torch – typically propane fuelled.

The two ends of copper pipe to be joined must first be cleaned well with the wire wool. Any dirt or grease in the joint may cause it to fail and leak, so make a thorough job of it cleaning until all oxidation has been removed and the metal shines like a new penny.

Apply a little flux to the cleaned ends using a small brush and assemble the joint. Twist the pipe (or joint) backwards and forwards to help to spread the flux throughout the joint. Then, get everything perfectly lined up how you want the finished joint to be.

15mm end feed solder copper joint

Unroll enough solder (at least 12 inches) so that you can hold the tip of the solder against the joint and heat it with a blowtorch without burning your hand. It is a good idea to bend the last few inches of the solder at a right angle to make it easier to apply it to the back and underside of the joints.

Apply heat to the whole joint with the blowtorch starting with the fitting and then moving the blowtorch flame backwards and forwards over the joints with the copper pipe. When the flux starts to bubble and smoke a little, remove the blowtorch and touch the solder at a few points all the way around the ends of each joint.

Soldering a joint in copper pipe

Solder will be drawn into the small gap between the pipe and the joint by capillarity. Keep applying solder until there is a perfect ring of solder around the mouth of the fitting. All ends of the joint must be made at the same time since if you do one end, let it cool, and move onto the second end, the first end joint will fail when the fitting is reheated.

To give a clean professional finish, quickly rub off any excess solder from the joints using a slightly damp cloth, but be careful as the joint will still be very hot.

UK Plumbing Suppliers

Ideally buy your copper pipe and fittings from your local plumbing merchant so you can get some good free practical advice at the same time, however, it is certainly possible to purchase everything you need online, and get it delivered to your doorstep at a great price.

There are some great offers on copper end feed fittings at eBay UK – click here to search now for end feed – but once you factor in the free delivery, placing an order for everything you need with Screwfix is usually more cost effective.


While it was very nice to see an article on pipe soldering I think a couple of point have been missed.
1. Clean the inside of fittings (most important as some are filthy)
2. The use of a fittings and/or pipe bush will help the less experienced get an easier and better success rate.

November 22nd 2008