It is not always practical to carry out a permanent repair immediately on a leaking pipe.
Isolate the water supply to the pipe concerned and drain it down.
A temporary repair can be effected until a permanent repair is possible.
There are two simple techniques which can be employed for this.
Pipe repair using hose and clips
Take a piece of garden hose of sufficient diameter to go round the pipe. Cut it lengthways and place it over the damage. Fasten with at least three jubilee clips. One in the centre and one at either end. By tightening these sufficiently, you should be able to seal the hose against the pipe so that no further water escapes.
Pipe repair using epoxy putty
Alternatively, use a proprietary brand of epoxy putty. This is a two-part mix which dries hard and will bond itself to most metals provided they are dry. Clean the area of pipe either side of the damage, with emery paper - the putty may not stick otherwise. Mix the two components together as detailed in the manufacturer’s instructions. Press it into place over the damage and smooth it out with a small filling knife. Check to see what thickness is required and also how long it should be left before allowing water to flow through the pipe again.
Whilst a temporary repair can overcome the immediate problem, it is always advisable to carry out a permanent solution as soon as possible.
Drain the affected pipework. Cut out the damaged section and fit a new length of pipe with compression or solder fittings at each end.