The weakest point in any pipe-work is the joints. If copper pipe is involved, resealing a leaking joint is either a simple matter of tightening a nut, or soldering a joint. Joints in lead pipe are not really a DIY job.
Copper pipework is often connected by compression joints. With these a slight turn of the nut will generally compress the olive inside sufficiently to cure the leak.
Soldered joints are more of a problem as they cannot be re-sealed without first emptying the pipe and this means draining at least a part, if not all, of the water system. If you are dealing with a hot water pipe (other than central heating), tie up the ball valve in the cold supply tank so that the water can be drained off at the taps. For central heating turn off the boiler and open the drain cock. A cold water pipe only needs the water turned off at the main stop tap. Even with the system drained, there may still be some water in the pipe.
There’s no point in simply trying to resolder the joint — the pipe will be dirty inside the fitting. And you need a clean and shiny pipe if the solder is to grip. You also need a new capillary joint that does the same job as the old. But you may not need an identical fitting; if the original was the type that uses a separate solder supply, buy the pre-soldered kind instead as they are easier to use.
1. The best method of taking the joint apart is to make a cut right through the centre of the fitting with a hacksaw and let any water out.
2. Then heat the pipe fitting with a blowtorch to melt the solder and allow you to pull out the ends of both sections of pipe. You may have to loosen some pipe clips in order to spring the pipe enough to get it free.
When using the blowtorch. You must take great care not to damage the wall behind the pipes. The best way to do this is to tape a piece of asbestos to the wall. The type of asbestos mat used by plumbers is expensive, and an excellent substitute is an asbestos simmering pad found in most good kitchenware shops.
3. Clean the pipe. Thoroughly with wire wool or abrasive-paper making sure that all the old solder is removed. Smooth the cut ends with a file.
4. Coat the pipe with flux to keep it clean. Clean the new fitting before sliding it over the ends of the section of pipe.
5. When it is in place heat it with a blowtorch until the solder appears around the end of the fitting. Indicating a fully soldered joint.
An easier solution may be to replace the existing solder joint with a compression fitting which needs no heat.
6. The compression fitting has a nut at each end with a ring, or olive. Inside. First push tha nut and then the olive onto the end of the pipe which must be clean and smooth.
7. Push the pipe into the fitting as far as the moulded stop. Then push the olive into the end of the fitting.
8. As you screw the nut up, the olive is forced into the fitting and compressed onto the pipe, forming a water tight joint. Tighten the nut as far as you go by hand — then give it a few further turns with an adjust-able spanner.
Lead pipe is more difficult to repair. You must scrape the pipe clean and cover the bright area with tallow flux. You then melt a plumber’s solder onto the pipe and wipe it in to the traditional shape using a coarse cloth coated with tallow.
Don’t tackle this job unless you feel confident you can handle it use an epoxy filler to make a temporary repair, then call a plumber.