Buying, Selling, and Decorating Your Dream Home

The Most Common Plumbing Problem And How To Deal With It – Full Guide


Plumbing is often one of the most daunting of DIY subjects. People are often afraid of messing up and having water spraying everywhere or even worse causing a gas leak. Obviously you should hire a CORGI registered professional plumber for gas work and more complicated jobs, but there are lots of smaller plumbing jobs to get your teeth into around the home.

From fixing leaks and dripping taps, through to clearing blockages and dealing with central heating problems, we give you step-by-step advice on getting things done with the minimum of fuss.

And of course, if you decide that you’d like to take on even more plumbing tasks, check out the extensive plumbing section of our in depth DIY site.

common Plumbing Problem

Leaks & Drips

Even the best-designed and best-installed plumbing system can leak – usually from a pipe joint, but occasionally from the pipe itself.Taps can drip or stop working altogether, and you can get strange noises from the plumbing and heating systems.

Leaks need to be dealt with as soon as they are discovered, whether in a pipe, a joint, or from a radiator. Not only do leaks waste water, but they can also cause damage to decorations and to house timbers that may develop rot as a result.

Repairing Leaks

Leaking Joints

Joints between pipes are often the first thing to go when pipework freezes and expanding ice inside the pipe forces the joint apart. If the joint is a compression joint with a nut on each connection, tightening the nuts (clockwise) will normally stop the leak.

Always use one spanner to hold the fitting whilst you use another to tighten the nut – but don’t overtighten it or it will distort the olive and leak again.

If tightening doesn’t work, you will need to turn the water off to isolate the pipe affected, dismantle the joint, and replace the compression olives (the shaped brass rings that are compressed to make the seal); the old ones may have to be cut off carefully.

Soldered capillary joints where the seal is made by a solidified solder between pipe and fitting – are more difficult to repair. They need heat, provided by a blowlamp, first to melt the old solder and then to melt the new solder on a replacement fitting.

The easiest thing to do is to turn the water off and cut out the leaking fitting and the pipe on either side, replacing the capillary fitting with a compression or push-fit fitting.

Leaking Pipes

Copper and plastic pipes do not normally leak unless they have been damaged in some way – either by piercing, typically with a floorboard nail or by bursting after they have frozen.

You can buy pipe repair clamps and repair putties (which set hard) to act as temporary stop-gaps, but the best solution is to turn the water off to isolate the pipe in question, cut out the affected length of pipe, and insert a new length with two straight couplers.

A proper pipe cutter is better for cutting the pipe since a hacksaw can leave a jagged edge. You can get special compact cutters to cut pipes next to a wall.

If the pipes are rigidly fixed (making insertion of the couplers impossible), make sure at least one of the straight couplers is a slip fitting – this has no internal shoulders, so can be slid up one of the pipes and then slid back into place after the new length has been inserted. You can get long single slip fittings, for replacing a short length of pipe.

Watch also the video below.

Dripping Taps

When it starts getting difficult to turn a tap off, you can suspect that the washer inside is getting worn – and when the tap starts dripping, you will know it is time to change the washer.

Fortunately, this is usually relatively simple and inexpensive, unless the tap is a modern ceramic disc type that requires only a quarter turn to operate.

These are much less likely to go wrong, but when they do, giving more of a stream than a drip, you have little choice but to replace the whole mechanism inside.

Replacing The Washer on a Standard Tap

Old-fashioned pillar taps have a vertical inlet and a rising spindle with a washer at the bottom. They usually have a bell-shaped cover topped by a capstan head (four prongs in a cross shape). Conventional modern taps have shrouded heads.

  1. Turn off the water to isolate the pipe leading to the tap.
  2. Remove the cover. With capstan-head taps, unscrew and lift off the head before removing the chromium-plated bell cover (you may need to use a cloth-wrapped spanner if it is tight). Shrouded-head taps and mixer taps usually have a coloured disc in the top of the tap head, which you unscrew by hand or prise out with a small screwdriver to get at the securing screw underneath to get the head off.
  3. Use a large spanner to undo the largest nut you can see. Use another spanner or a piece of wood to brace the tap as you unscrew this to avoid cracking ceramic basins or baths.
  4. Take out the works of the tap. You should see the tap washer on the bottom. Prise this off – you may need to undo a small nut – and replace with a new one of the same size and shape (bath taps have bigger washers than basin taps).
  5. Re-assemble everything before turning the water back on.
  6. If a tap is leaking from the top when it is opened, tightening the smallest nut you can see will normally stop the leak, but you may need to dismantle the tap, by undoing this nut or prising out the circlip, to replace the sealing 0 ring.

Watch the video below for more about this

Mixer Taps

Replacing washers on mixer taps is the same as for single taps, though you will need to turn off both hot and cold supplies if you are replacing both washers.

Mixer taps can also leak around the spout, caused by a failed 0 ring. If you can find the tiny grub screw that you undo to remove the spout, replacing this is simple.

Sealing Round a Bath

Water that gets down the gap between a bath or shower tray and the wall can cause damage to the floor underneath (possibly rot) but can be prevented by applying silicone sealant around the rim of the bath or shower tray.

Silicone sealant comes in white and various colors and requires a bit of skill to apply. You can use either a large cartridge in a caulking gun or a smaller cartridge with its in-built plunger.

To get a smooth result, do a dry run first: without actually applying sealant, run the cartridge all the way around the edge of the bath or shower tray to check you can do this in one continuous action without having to break to change position.

WCs (Water Closet) & Cisterns

When a water closet (WC) doesn’t work properly, the problem usually lies in the cistern, not the pan. Fixing WC problems is straightforward, even if you have no plumbing know-how – as long as you understand how the flushing mechanism works.

You just need a few basic tools and some inexpensive spare parts. Even getting access to the problem area is easy, just lift off the cistern lid. Cisterns in the loft can have problems, too – usually too much noise or a dripping overflow pipe.

How a Water Closet Works

When a water closet is flushed, two things happen:

How a Water Closet Works

1.Water in the cistern flows down a connecting pipe into the WC pan.

This happens because of a siphon mechanism at the bottom of the cistern, activated by a rod connected to the far end of the flush lever spindle. The siphon action starts when a unit containing a piston and a flexible plastic diaphragm (flap valve) pushes water through an upside-down U-bend.

The piston then drops back, allowing the water to flow past it until the cistern is almost empty and the lack of water stops the siphon action.

2. The cistern refills through a ball valve near the top of the cistern.

This valve is operated by a metal or plastic arm connected to a float, which sits on the water. As the water level falls, the float arm falls with it, opening the valve and allowing the cistern to refill.

As the water level rises, the float arm rises too, and the valve closes. Similar ball valves are fitted to water storage cisterns in the loft.

If The Cistern Doesn’t Flush

If the cistern doesn’t flush, either there’s insufficient water, or the siphon mechanism isn’t working.

1. The float arm may be set too low.

  • Check the water level inside the cistern. It should be about 25 mm (1 in) below the bottom of the overflow pipe. The correct level might be marked on the inside wall of the cistern.
  • If the water level is too low, the float arm is also too low and is closing the ball valve on the water inlet pipe before the cistern is full.
  • If the float rod is metal and has no adjuster screw, straighten it slightly.
  • If it is plastic, there will be a small adjuster screw on the arm – turn it anti-clockwise to raise the arm.

2. The C-shaped wire link between the flush lever spindle and the lift rod has become disconnected.

  • Re-hook the wire link on to the flush lever spindle and the top end of the lift rod.
  • If the link is broken, replace it.

3. If a WC still doesn’t flush effectively, you probably need to replace the siphon unit flap valve (the flexible piece of plastic on top of the perforated plate).

  • On a separate cistern, where the cistern is joined to the lavatory by a pipe, tie up the float arm to stop the cistern refilling.
  • Flush cistern and mop up the remaining water.
  • Disconnect the flush pipe from the base of the cistern and undo the large nut that holds the siphon unit to the base of the cistern.
  • Unhook the wire link from the top of the siphon lift rod.
  • Lift the siphon unit out and pull out the lift rod and piston from the open base.
  • Remove the old flap valve and fit a replacement.
  • Cut the new one down to size with scissors if it’s too big.
  • Reassemble everything.
  • Untie the float arm so the cistern can refill.

4. On a close-coupled cistern, where the cistern and lavatory pan is joined, replacing the valve itself is the same as for a separate cistern, but to get at the nut that holds the siphon unit to the base of the cistern, you first have to remove the cistern from the pan.

  • Turn off the water supply to the cistern.
  • Flush the cistern and mop up the remaining water.
  • Disconnect the supply and overflow pipes from the cistern.
  • Undo the screws holding the cistern to the wall, and also the two wing nuts securing it to the rear part of the pan.
  • Lift the cistern off the pan.
  • Unscrew the siphon securing nut.
  • Unhook the wire link, lift out the siphon unit, lift rod and piston, and replace the flap valve as for a separate cistern.
  • Reassemble everything and restore the water supply.

See also this video

If an Overflow Drips

If water is dripping or running from an overflow pipe outside, one of your cisterns is overfilling, sending water down the overflow – find out which one before checking the possible causes.

Clearing Blockages

The first you are likely to know about a blockage is when a sink, basin, or WC won’t empty, or gullies and manhole covers are overflowing outside, usually accompanied by a strong smell.

The blockage may be in one of the several places. If there is a strong smell but no evident blockage, ask your local Environmental Health department to check the drains.

Waste Outlets & Pipes

Sinks, basins, baths, shower trays, or bidets that won’t run empty are all indications of a blocked waste system.

1. Plugholes

The metal grille over the waste outlet – usually called the plughole – is designed to prevent material (such as hair or vegetable peelings) getting into the pipes so that it may get partially blocked quite often. Cleaning it out is simple, but you may need to pull bits of hair out by hand.

2. Waste Traps

Waste Trap

The shaped waste trap underneath a waste outlet remains full of water all the time. It prevents smells from the drains getting into the house and prevents small creatures climbing in. Bottle traps take up less room than conventional tubular P-traps, but are more likely to get blocked – and should never be fitted below a waste disposal unit. If your bottle trap gets blocked regularly, replace it with a P-trap.

Clearing a Blocked Trap

First try a hand-operated force pump or a simple rubber, cup-shaped sink plunger. This fits over the waste outlet and is pumped up and down vigorously, creating water pressure that may force out the blockage. Hold a damp cloth over the overflow outlet at the top of the basin or sink while using the plunger or force pump to create a vacuum. You may need several goes to clear the blockage.

If a plunger or force pump doesn’t work, you can dismantle the trap. Place a large bucket underneath it and undo the nuts holding the ends of the trap on to the waste outlet and the waste pipe leading outside. Be prepared for the contents of the sink or basin to gush out. Clean the trap itself with washing-up liquid and an old bottle cleaning brush (using a different basin in the house) and re-fit it, smearing a bit of liquid soap on to the rubber sealing rings. Empty the bucket outside and check that the trap is clear by running fresh water from the taps.

3. Waste Pipes

If plunging and cleaning the trap doesn’t work, the blockage is further down the waste pipe. Remove the trap again and use a plumber’s snake – a length of flexible wire with a wiggly bit on the end, also known as a sink auger – pushed down the waste pipe to clear the blockage.

You can use the wiggly bit to disturb the blockage, pulling and pushing it until you can get the snake all the way through the pipe. Re-fit the trap and test for clear running.

4. Soil Pipes

If a soil pipe is on the outside of the house, it may get frozen in the winter, especially if you have a dripping tap inside. Otherwise, blockages in outside soil pipes are rare.

Hopper heads in older systems may sometimes get clogged with soap and hair, but are easy to clean out provided you have a safe way of getting to them.

On modern soil pipes, there is usually an access hatch somewhere that you can unscrew to get a plumber’s snake or a drain rod inside to clean out blockages. Stand well back when you open this – there could be a sudden gush of filthy water.

5. Water Closet

A blocked water closet (WC) is something you will want to deal with as quickly as possible. You can get larger versions of sink plungers and force pumps to use, which have long handles, so you do not need to get too close to the blockage.

If you have no success with these, there is similarly a larger version of the plumber’s snake (see Waste Pipes), called a WC auger.

Push this down the WC pan until you reach the site of the blockage, which can then be disturbed and cleared.

Underground Drains

The most obvious sign of a blocked underground drain is an overflowing gully outside, but be suspicious if there is a very strong smell anywhere outside your property.

This could mean there is a blockage in the drain itself or one of the inspection chambers situated under manhole covers.

Underground Drains

The Gully

If there is no indication where the blockage is, start by clearing the gully under the kitchen sink waste outlet, where the downpipe from the kitchen empties into the drain. In older houses, this may take the waste from the bath and bathroom basin as well.

Be prepared for a horrid job – wear stout rubber gloves to scoop out the gunge from the gully after lifting up the grille. If the blockage is in the gully trap, you may need a plumber’s snake to winkle it out.

The Drainpipe

If water will still not flow away after clearing out the gully under the kitchen sink waste outlet, lift all the manhole covers and look inside the inspection chambers, some of which may be full. The blockage is in the drain between the last full chamber and the first empty chamber.

Hire a set of drain rods. Join the first couple of lengths to the worm screw attachment that comes with them and lowers this into the last full inspection chamber, feeling for the half drain that runs along the bottom toward the outlet away from the house.

Push the worm screw into the outlet and along the drain in the direction of the empty chamber, adding more rods as you need them until you reach the blockage. A combination of pulling, pushing, and wiggling the worm screw should dislodge the blockage, allowing the inspection chamber to empty.

The other attachments that come with a drain rod set – such as a plunger and a scraper – can be used to clean out the drain once the main blockage has been removed. If you encounter an obstruction that will not give way, the drain may be blocked by a tree root or broken drain material, and you should call in professional help.

If it is the last inspection chamber before your property boundary that is full – probably by just one third – you have a blockage between this inspection chamber and the main sewer. Rod this inspection chamber as before, pushing the worm screw along the base of the chamber away from the house, wiggling it until the chamber empties.

If you have a cesspool or septic tank and the last inspection chamber is full, it’s time to have the pool or tank emptied.

On some modern drainage systems, you may have one or more ‘rodding points’ rather than inspection chambers. The small circular covers of these can be removed to allow you to insert drain rods.

Using Drain Rods

  • Always twist drain rods clockwise. Twisting them anticlockwise could make the rods unscrew underground, and you could lose one.
  • Clean the rods with water and disinfectant after use.

Central Heating

Central heating is wonderful when it works, but can be a nightmare if it goes wrong.

A problem may be due to the failure of one or more of the components – boiler, pump, controls, or immersion heater – or something going on inside the system, particularly the onset of corrosion, which is caused by different metals being in contact through the water.

Many of the problems that arise with central heating can be dealt with relatively simply, but some may call for the services of a professional contractor.

Central Heating

Draining and Refilling a Heating System

You may need to drain and refill your central heating system if you want to move radiators or replace them with others of a different size, requiring changes to the pipework, or if you want to treat corrosion.

A central heating system that uses water (the vast majority) will have at least one drain valve that allows you to empty out the water. The drain valve will usually be at the lowest point in the system, possibly under the floorboards, but there may be additional drain valves by the boiler or where pipes are looped down from the first floor to a ground floor radiator – often the case with kitchen radiators.

Draining the System

  • Switch off the central heating.
  • Close off the water supply to the feed-and-expansion cistern to stop the system re-filling. To do this, you can either turn off the water at the main stop valve or tie up the ball valve in the feed and expansion cistern – a better option since it allows you to continue using the kitchen cold tap. You can release the ball valve any time you want to flush the system through with fresh water. You might need to do this after using a cleanser before adding corrosion proofer.
  • At each drain valve (it doesn’t matter where you start) attach a hosepipe to the outlet of the valve and lead the hose outside or into a bath.
  • Using a small spanner, unscrew the valve, allowing water to flow out.
  • Unscrew the air bleed valve on every radiator to make sure all the water is removed. You will need to include the air bleed valve on the hot water cylinder. This is usually located on the highest point on the upper of the two pipes that lead from the boiler into the side of the cylinder.
  • While the system is empty, you might want to remove individual radiators, take them into the garden and flush them through with water from a garden hose.

Refilling the System

  • Again with the heating system turned off, close all the drain valves and air bleed valves and release the ball valve in the feed-and-expansion cistern.
  • As the system fills, bleed each radiator in turn, starting with those on the ground floor and working upwards. You may need to go round the whole system twice, not forgetting the air bleed valve on the hot water circuit next to the hot water cylinder. Corrosion proofer is added on the final fill after cleansing and flushing (check instructions supplied with corrosion proofer for details).
  • When the system is full, turn the boiler on and check that there are no leaks from any of the air bleed valves or drain valves – tighten any that are leaking.

Watch also this video

Removing and Replacing a Radiator

If an individual radiator has sprung a leak or is too small or large, it is normally a fairly straightforward task to replace it. The easiest job of all is where the replacement radiator has its inlets in the same place and can be hung on the original wall brackets, which is much more likely if it is the same make as the one being replaced.

If the existing radiator has an inappropriate heating output, it can be replaced with a different type of the same size (with fewer or more panels or fins) or by one of the same type that is a different height, but not a different length.

A new radiator that does not fit the old wall brackets will still not be too complicated to install, but if the new inlets are in a different place from the old, the system will need to be drained so that the pipework close to the radiator can be altered –  something that is likely to need the skills of a qualified plumber.

You will need something to catch the water that falls out of the radiator when you remove it – put down towels on the floor and have bowls ready for catching the water from each valve.

  1. Close the handwheel or thermostatic valve that turns the radiator on and off: if your radiator has a thermostatic valve, set it to 0 to close it.
  2. Remove the cover on the valve at the bottom of the other side, called the lockshield valve (this usually needs a screwdriver) before closing that. If the handwheel from the first valve fits the lockshield valve, you can close it with that. Otherwise, you will need to use a spanner.
  3. With both valves closed, open the air vent at the top of the radiator and unscrew the two nuts that join the valves to the radiator, with the bowls ready to catch the water.
  4. Bend the valves out of the way so that you can lift the radiator off its brackets and tilt it to drain fully.
  5. If the new radiator is the same size and make, you should be able to re-use the existing wall brackets, but otherwise you will have to unscrew the old brackets and drill holes in the wall to take wallplugs for the new ones. Full instructions should be given with the radiator for getting these in the correct position).
  6. Remove the screwed tails (the connections that take the valves) from the bottom tappings of the old radiator and fit them in the two bottom outlets of the new one – you may need a special radiator spanner to do this.
  7. Also fit the blanking plug and air bleed valve supplied with the new radiator to the two inlets at the top.
  8. Hang the new radiator on the wall brackets and connect up the two valve tails, making sure the nuts are tight.
  9. Open up the handwheel and lockshield valves – turn a thermostatic valve to the setting you want – and use a radiator key on the air bleed valve you fitted to the top of the radiator to allow the air inside the radiator to escape once the water starts running into it.

Possible Problems With Temperature

If you cannot get some rooms to the right temperature, or some rooms are always warmer than others, you may have one of some problems.

Some radiators are too large or small for the room.

The heat output of a radiator depends on its surface area, so the larger it is – in other words, the more panels and fins it has – the greater the amount of heat.

For the same size (length and height) of the standard radiator, there are four choices of design (in increasing order of output):

  • single panel
  • single panel with fins
  • double panel with one set of fins
  • double panel with two sets of fins.

You can usually replace the existing radiator with one of the same size but with a higher or lower output.

The radiators are imbalanced.

There may be too great or too little flow through some of the radiators. The amount of water flowing through a radiator is controlled by the setting on the lockshield valve.

Remove the cover, then turn the spindle of this valve either with a spanner or, if it fits, with the handwheel from the other valve. Turn the valve clockwise to reduce the water flow and so reduce the heat output, turn it anti-clockwise to increase the flow and output.

Getting the balance exactly right requires the use of two inexpensive clip-on thermometers (available from plumbers’ merchants), which you apply to the pipes leading to the radiator, but trying different settings may be sufficient.

The room thermostat is in the wrong place.

The heating for the radiators is turned on and off by the action of a room thermostat – an electrical switch which starts the boiler and the pump when the air temperature around the thermostat is too low and turns them off when the surrounding air reaches the temperature you have set on the thermostat.

The thermostat can be fooled if it is in a draught or direct sunlight, or in a room that has additional heating. If you find that some rooms are too hot and others are too cold, it could be that the thermostat is in the wrong place: the best place is usually in the hall out of direct sunlight and away from draughts.

You will need an electrician to move it.

Corrosion in the Heating System

Corrosion in the Heating System

A fateful combination of metals in the central heating system can cause corrosion. It will lead to some or all of some symptoms:

  • leaks, where corrosion has eaten away the steel of the radiators
  • cold at the bottom of radiators, from a build-up of sludge
  • cold at the tops of radiators, because hydrogen gas has collected there
  • malfunctioning pumps and motorized valves, which can jam from corrosion
  • various extraneous noises in the pipes and the boiler.

Preventing corrosion is very straightforward in a new system or an old one that is still in good condition by adding corrosion proofer to the feed-and-expansion cistern and allowing it to circulate throughout the water.

Dealing with existing corrosion is a two-stage process: first cleaning out the existing system, and then adding the corrosion proofer.

Find out from the manufacturers of corrosion proofers, or a good plumbers’ merchants, which cleansing and corrosion-proofing products you need – it depends on the type of boiler you have.

Copious instructions are provided with the proofers on how to use them, but you will need to know how to drain and refill your central heating system.

Preventing Freezing in an Empty House

In a house that is normally occupied during the winter, there should be no danger of frozen or burst pipes. But if a house is left empty for anything more than a day during a cold snap, there is always the possibility that some pipes will freeze and that some may even burst as they thaw.

There are specific precautions you need to take to prevent this, depending on how long you are going to be away.

Away for a Weekend

If you are only going to be away from the house for a couple of days, you can either leave the heating on its normal settings and be prepared to pay the fuel bills or, if you want to save money, do the following:

  • set the heating programmer to 24-hour (‘continuous’) operation
  • set the room thermostat to a low setting, say 5°C/41°F
  • remove or prop loft hatch fully open.

This will allow the boiler to fire to keep the house (and the loft space) above freezing point.

Away for Longer

If you leave the house for more than a few days and want to turn the heating off, you need to drain the hot and cold water systems of all water. If the heating system (which is separate from the hot and cold water systems) has anti-freeze in it, you do not need to drain it.

  • Drain down the cold water system entirely – close the main stop valve, open all cold taps, and flush all WCs.
  • Drain down the hot water cylinder fully using a length of hosepipe attached to the drain valve at the base of the hot water cylinder (which needs a small spanner to open); put this into a basin or bath, and open all hot taps.
  • When you return, check that all drain valves are closed before opening the mains stop valve.
  • Close taps as water flow from them – the kitchen cold tap first, then all other cold taps, and then all hot taps.

General Precautions

Whether you are planning to be away or not, it’s sensible to take general precautions against freezing in case you are away during a cold snap and haven’t been able to prepare for it first. There are two general ways to prevent freezing:

  1. Fit a frost thermostat that brings the boiler on whenever the air temperature drops below a certain level – much lower than the level required to bring the heating on when the house is occupied. This is certainly something you should do if the boiler is situated in the garage or an outhouse that could get seriously cold even if the rest of the house is above freezing.
  2. Add anti-freeze chemical to the feed and expansion cistern so that it circulates around the central heating system. This chemical is made by specialist firms – and is not the same as the antifreeze used in cars.

Adding antifreeze to your central heating system or fitting a frost thermostat are useful general precautions against freezing pipes, but you should still take the specific precautions described above if you go away in the winter to prevent the house water pipes freezing.

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