Module 2 of 2 · 45 minutes
Joints, leaks and the repairs worth doing yourself
By the end of this module you will be able to
- Choose between soldered, compression and push fit joints and justify it
- Make each joint type properly, and know what makes each one fail
- Diagnose a leak by where and when it appears
- Recognise the work that must never be attempted without registration
Work through it
1 interactive for this module, built on the WAJD Teach engine. Nothing moves until you ask it to, and every one has a written version if you would rather read it.
Amara Before we start on joints, what is the hard line?
Nadia Gas. Under the Gas Safety Installation and Use Regulations 1998, only a Gas Safe registered engineer may work on gas fittings and appliances.
Amara Not a competent amateur.
Nadia Not a competent amateur, not a confident plumber, not you. That includes the gas supply to a boiler, gas cookers, gas fires and the pipework serving them. It is a criminal offence, it voids buildings insurance, and carbon monoxide from bad gas work kills people every single winter.
Amara Is there anything I may do?
Nadia Turn it off in an emergency, and work on the water side of a wet system. That is the whole boundary and it does not move.
Amara And if I smell gas?
Nadia Do not touch any electrical switch, not even to turn a light off. Open windows, turn off at the meter if you can safely reach it, get out, and ring 0800 111 999 from outside.
Amara Right. Joints. There are three kinds and I have never known which to use.
Nadia Match the joint to where it is going. Soldered capillary joints are the strongest, cheapest and neatest, so they belong anywhere the joint is going to be forgotten about. Inside a wall. Under a floor.
Amara What makes a solder joint fail?
Nadia Three things, and it is always one of them. The pipe was not clean. There was water in the line so it never got hot enough. Or somebody nudged it while it was cooling.
Amara How do I get it right?
Nadia Clean pipe and fitting to bright copper, flux both, and then heat the fitting, not the solder. Let capillary action draw it in. If you are melting solder with the flame you are doing it wrong.
Amara Compression?
Nadia Demountable, no flame, so it is right where a blowtorch is dangerous or where you might need to take it apart. And it is ruined by exactly one thing: over tightening.
Amara Everyone over tightens.
Nadia Everyone does, because it feels like security. You crush the olive out of shape and it will never seal again. Tighten until it bites and then usually not more than a turn. Then test it rather than heaving on it for insurance.
Amara And push fit? Real plumbers seem sniffy about it.
Nadia Some are, and they are wrong. It is fast, it tolerates a damp pipe, and for a repair under a floor on a Sunday it is excellent. It fails for three reasons and all three are avoidable.
Amara Which are?
Nadia The cut was not square. The pipe was not pushed fully home. Or somebody left the insert out of plastic pipe. So: deburr it, mark the insertion depth on the pipe with a pencil, and push until your mark disappears.
Amara Let us talk about finding leaks. Water appears on a ceiling and I have no idea where it came from.
Nadia Then read the timing first, before you open anything. Constant drip whatever you do means the supply side, because that is under pressure all the time. Only when a tap runs or an appliance drains means the waste side.
Amara And only when the heating is on?
Nadia A heating circuit joint opening up as it expands. That one drives people mad in summer because it does not leak at all.
Amara What about the ceiling stain?
Nadia Almost never directly under the source. Water tracks along a joist and drops at the first low point. So look higher and to one side, and do not start cutting the ceiling out where the stain is.
Amara Last thing. What is worth learning to do myself?
Nadia Tap washers and ceramic cartridges, traps, toilet fill and flush valves, isolating valves, flexible connectors and blockages. That is the very large majority of every callout a domestic plumber attends.
Amara Any habit that helps?
Nadia Three. Fit an isolating valve while you are in there. Photograph it before you dismantle anything. And lay the parts out in the order they came off. The plumber's bill is rarely the part.
The written material
Gas: the line that is not a judgement call
Before anything else. Under the Gas Safety (Installation and Use) Regulations 1998, only a Gas Safe registered engineer may work on gas fittings and appliances. Not a competent amateur, not a plumber who is confident, not you.
This includes anything connected to a boiler's gas supply, gas cookers, gas fires and the pipework serving them. Doing it unregistered is a criminal offence, it invalidates buildings insurance, and carbon monoxide from bad gas work kills people every winter.
You may turn gas off in an emergency and you may work on the water side of a wet system. That is the boundary and it does not move.
Three joints, three failure modes
Soldered capillary joints are the strongest, cheapest and neatest, and they are what you want inside a wall or under a floor where a joint must be forgotten about. They fail when the pipe is not clean, when there is water in the line, or when the joint is disturbed while cooling. Clean the pipe and the fitting to bright copper, flux both, heat the fitting rather than the solder, and let the joint draw the solder in by capillary action.
Compression joints are demountable and need no heat, which makes them right where a flame is dangerous or where the joint may need to come apart. They fail from over tightening, which distorts the olive, and from being used on pipe that is not round or is scored. Tighten until it bites and then usually no more than a turn beyond, and check rather than heaving on it.
Push fit is fast, tolerant of damp pipe and excellent for repairs and for plastic pipe. It fails when the pipe is not cut square, when the pipe is not fully inserted to the depth mark, and when a pipe insert is omitted from plastic pipe. Deburr, mark the insertion depth on the pipe with a pencil, and push until the mark disappears.
- Soldered: strongest and cheapest, needs a dry clean pipe and no movement while cooling
- Compression: demountable, no flame, ruined by over tightening
- Push fit: fast and damp tolerant, needs a square cut, a full insertion and an insert in plastic
- Never conceal a compression or push fit joint where it cannot be inspected if you can avoid it
Reading a leak
Where and when a leak appears tells you most of what you need before you open anything up.
Constant drip regardless of use: a supply side leak, under pressure all the time. Only when a tap runs or an appliance drains: a waste side leak, which is not under pressure. Only when the heating is on: a heating circuit joint expanding. Appearing at a ceiling some distance from the bathroom: water tracking along a joist, so the source is usually higher and to one side rather than directly above the stain.
A slow rise in a water meter reading with everything turned off means a leak somewhere on your side of the stop tap, and that is worth chasing before it finds a wall.
The repairs worth learning
Changing tap washers and ceramic cartridges, replacing a trap, replacing a toilet fill or flush valve, fitting isolating valves, replacing a flexible connector, and clearing a blockage cover the very large majority of domestic plumbing callouts.
The habit that makes all of them easier: fit an isolating valve while you are in there, take a photograph before dismantling, and lay parts out in the order they came off. The cost of a plumber is rarely the part.
Knowledge check
The knowledge check and your certificate need a free account, so that your progress and results can be saved as evidence.
The learning itself stays free and open. You are reading all of it right now without an account.