The water from the waste outlet in sinks and baths etc should drain reasonably quickly and freely. If the flow becomes slow, it indicates a blockage beginning to build somewhere in the pipework.

Since these waste pipes have to deal with everything from leftover bits of food to strands of hair, it is hardly surprising that they block up from time to time.

You can try using a proprietary drain cleaner to prevent the build up of such blockages. Be sure to follow the instructions and safety precautions carefully as they are caustic. They should not be left to act for an excessive time.
 
Using a plunger

A plunger is a simple device, but very effective if used correctly. There are several types available including pump action ones. . Smear petroleum jelly around the base of the plunger this helps seal it against the bottom of the bowl. Place the plunger over the outlet and run the water so that there is enough in the bowl to cover the base of it. Now, holding a wet cloth over the overflow, pump the plunger several times. Remove it and see if worked. Repeat as necessary.
 
Blocked waste trap

Although the last method can be very effective, the action can just push the blockage along the pipe a little, but may not release it.

Frequently the blockage will be in the trap beneath the sink. The quickest way to remove it is to clean out the trap. Place a washing-up bowl under the trap to catch the water. Remember not to switch on the taps again until it's replaced. Unscrew the two ends of the trap and ease it out. Clear any debris from it. If this is where the blockage was, you will clearly see it. Reassemble the trap and check the flow of waste water again.
 
Rod out the blockage

If the blockage has not been removed, it will be necessary to the pipe out. This can be done from an access cap, which will have been fitted at any sharp junctions in the waste pipe if it was installed by a thoughtful plumber. Failing this, you can remove the trap again and access the pipe run from here. Have a bucket standing by and protect the area beneath. A blocked pipe may be holding a fair bit of dirty water.

If the blockage is near, it is often possible to remove it using a straightened wire coat hanger with a small hook shaped at the end.

More awkward to reach blockages will require the use of a narrow gauge drain rod. This is usually a long length of wire on a reel with a hook set on the end. It is pushed into the pipe until it reaches the obstruction and then twisted to release it.Once cleared, replace the trap or access cover and test the flow of waste water.
 
Gullies

The gulley can easily become blocked with a build up of leaves and other debris.Remove the grate. If you have use of a rodding auger, this can be used as for rodding a soil pipe by inserting it and turning the handle.If you do not have one, protect your hands with thick rubber gloves before starting. There is every possibility of coming across sharp objects.Remove as much water as you can using an old plastic container. Then reach into the gulley, which is like a giant version of the trap under your sink. Fish out the debris until the bend is clear. Flush through with running water before replacing the grate.

 

Clearing blockage - toilet and soil pipe 
 
With all drain work it is sensible to wear rubber gloves for hygiene purposes. You should disinfect your hand and all equipment after completing the work.
 
WC

If the water from a WC fails to drain away easily or, worse still, overflows completely, there is a blockage. Frequently this will be in the water trap in the pan itself and can readily be cleared. But, before proceeding, check the flow from other waste pipes to establish whether the blockage is affecting all the pipes. If it is, then the obstruction will be further down the line. If not, carry on as follows. 
 Use a large plunger for this. Hold it so that the rubber end covers the waste outlet at the base of the pan and pump several times. Repeat as needed. Once the blockage is clear, the waste water should flow rapidly away  all downhill from here. 
 
How to rod out the blockage

If this doesn't clear it, the blockage may be further along, in which case, you can hire a large rodding auger to reach further along the pipework. This consists of a flexible rod which can be inserted. At the top is a mechanism for turning a claw at the far end using a winding handle at your end. Push the auger down the pipe until you feel it reach the obstruction. Then turn the handle to dislodge it.
If this fails to clear the blockage, it must be further along in the soil pipe or the drain run itself.
 
Unblocking a soil pipe

Old cast iron pipework rarely has serviceable access traps in it so the rodding out of such pipes may need to be undertaken via the vent, which is the top section on the roof. If this is the case, you may wish to consider employing a contractor unless you have sufficient skill and knowledge to access this pipe. Access to this vent pipe will be high up and therefore potentially very dangerous. Never attempt to carry out such work without safe access equipment. It is not safe to stand a ladder against the pipe as no lateral stability will be offered and the pipe may well give way.
Fortunately, on modern plastic systems, access points are provided at pipe junctions. Before unscrewing one of these, consider the consequences. It is quite possible that there is a column of sewage sitting in the pipe above and this will come out at quite a speed. Unscrew it slowly and do your best to contain the result. If the pipework is indoors, lay plenty of plastic sheeting and make provision for clearing up the water.
 Remove the access cover and insert a drain auger (available from hire shops). Feed the auger in until you feel it reach the obstruction. Then turn the handle and move the auger back and forth to dislodge the blockage. Withdraw the auger and flush the pipe with water from a hose. Replace the cover.

 

The indicators of a blocked drain are poor flow, seepage of waste from around the manhole, or smells coming from it.
To clear a blockage here, you will need a set of drain rods (available from hire shops).
If there is no indication of poor flow, smells may be due to an inadequate seal between the edge of the manhole cover and its frame. Inspect and repair as necessary.
 
Accessing the drains

Lift the manhole cover. This may be a two-man job as some covers are very heavy. There are usually two lifting points. These tend to get filled with dirt and debris and will need to be cleared. Depending on the type of cover, you may also need a cover lifting tool. This is a key type device which is inserted into the socket to enable the cover to be lifted.
When you lift the cover clear, you will see a pit through which the waste flows. One or more pipe runs may lead into it and one away from it.
If the manhole is full and you cannot see the outlet, you will need to judge at which end it is likely to be. This can usually be established by looking for other manholes and working out which one feeds which and therefore the direction of the outlet from the one you are dealing with. 
 
Using drain rods

Assemble several lengths of drain rod. If the outlet is an interceptor trap (like a large- scale version of the trap under the sink, use the rubber plunger end to pump the blockage through the trap. If it is a straight outlet, use the screw claw end. Push this down into the outlet, turning clockwise only. Turning counterclockwise will unscrew the rods and you'll then be faced with the task of their retrieval! When you feel it reach the obstruction, turn it gently and use it to push and pull. Be careful, as when the pipe clears, the retained waste water can be drawn away at quite a rate, pulling on the rod as it does so.
Remove the rods and flush the drain with water from a hose. Replace the manhole cover, making sure it sits flat in its frame.