Fixing and maintaining drains

If the trap is a modern plastic P or S type, unscrew the component parts and release the trapped debris. The same applies in the case of a bottle trap, though here you have only to unscrew the base. If the trap is of the older metal type, it should have a clearing eye somewhere on the U bend. Unscrew this carefully with a wrench then use a piece of coathanger wire to hook out the debris. When you replace the eye, wrap a piece of PTPE tape around the thread and take care not to overtighten it.

If the WC is blocked, you will not be able to get full suction except with a special large plunger but you may be able to create enough of a disturbance to dislodge the blocking material.

Drainage problems are inconvenient and can be extremely unpleasant to put right. But often the cause is simple and, if you can face the job, it is worth trying a cure yourself, rather than calling in experts—it could save both time and money.

Minor blockages

These plague all households at some time or another, so always have a simple plunger close to hand. In the case of a blocked sink, basin or bath first remove the waste plug. If you have the pop-up type, it may simply lift clear, perhaps with a quarter-twist; or you may first have to detach the horizontal pivot rod from underneath. Block the overflow with a damp rag, and place the plunger directly over the waste outlet. Pump vigorously for a few seconds. Should

Should this fail, be wary of poking sticks or stiff wire into the trap as these might get lost or may damage the pipe. A better solution is to buy or hire a purpose-made cleaning wire. These have a screw the business end which you can revolve from a spindle on the handle and are particularly effective on WC wastes.

Persistent blocking in and around waste traps—particularly the WC—is often the result of plaster or concrete debris having been poured down the drain at an earlier date. Again, a clearing wire is a good investment because you can use it periodically to erode the blockage and restore the pipe to its full diameter.

Another solution, which is often effective on kitchen sinks where persistent blocking is due to an accumulation of grease deposits in the pipe, is to pour down a proprietary clearing compound of the caustic soda type. Take great care when you do this however, and use the compound strictly in accordance with the manufacturer’s instructions.

Main drain blockages

The first signs of a major blockage are usually unpleasant smells in the kitchen or bathroom, strange gurgling noises whenever you discharge any waste, and the backing up of waste in open gullies—or even into Wcs or other fittings.

Be methodical in finding the location of the blockage—the rule is that the blockage must be below any point where there is trapped water and above any point where there is no water. In the UK, there are inspection chambers, or ‘manholes’ along the line of the drains, to help you.

Start with the chamber nearest the main sewer. This may have its own interceptor trap, which is often the cause of a large amount of major blockages. Suspect the interceptor if this chamber is full of effluent.

If the interceptor chamber is clear, the blockage lies further back along your drainage system—probably at the secondary chamber nearer the house. This marks the junction of various parts of the above-ground pipe work—generally the soil and waste pipes or the combined soil/waste and a gulley. Most houses have only one secondary chamber, though if the drainage system is particularly complex or where there are sudden changes in level, there may be more.

In some instances—in the case of an extension, for example—the chamber may actually be inside the house. In this position, it must be fitted with a double sealed cover and you will have to remove the fixing screws in order to open it up.

To clear a blocked secondary chamber, you must rod through the outlet on the main drain side and push the blockage down towards the interceptor chamber. At this point you may have to rod again to clear the blockage completely.

If the interceptor chamber itself is blocked, the blockage is likely to be in the trap and will have backed up to the secondary chamber or even further. In this case, the first step is to contact the health department of your local council who may clear the chamber free of charge.

If you must do the job yourself, look for the drainage stopper in the chamber wall at the downstream end. This may well be obscured by the effluent in the chamber but you should still be able to see the chain that holds it to the upper part of the chamber wall. Pulling on the chain will release the stopper and open the cleaning or ‘rodding’ eye that by-passes the trap. If the trap itself is blocked the effluent will disperse through the eye and leave the chamber clear for you to work in. And if the blockage is further down towards the main sewer, you can rod directly through the eye to clear it.

In some cases, there may be no stopper chain. If so, feel with a stick to see if the stopper is in place. If it is, bale out enough effluent to make it visible then remove the stopper by hand and proceed as above.

If feeling with the stick reveals that the eye is open, and you are very unlucky, the stopper may have fallen down into the trap. In this case you must bale out all the effluent, get down into the chamber, and try to extract the stopper by hand. If you cannot do so, the trap must be excavated—using powered tools to break up the stopper will more than likely damage the rest of the drain.

If the interceptor and the secondary chambers are both clear—which is very rare in the case of blockages— the blockage must be still further up the system and it should be quite obvious which waste pipe and appliance are affected. Unfortunately, unless you can clear the blockage by plunging from the appliance end, it would be best to seek professional help. Problems of this sort are nearly always due to a fault in the waste pipework—in which case only an expert will have the necessary experience to decide on a remedy.

Rodding drains

Rodding the drains is a simple, if unpleasant, job providing you can get hold of the proper equipment. Sets of rods can be hired quite cheaply, together with plunger and screw head attachments, from most hire shops.

When you begin, start with two or three sections and add more as you progress down the drain. Use the plunger head first, then the screw if you have no success. Pull the rods quite vigorously backwards and forwards in the pipe, at the same time constantly twisting them in a clockwise direction to keep the joints screwed tightly together.

Where to rod

The golden rule about rodding drains is always to rod in the direction of the main drain. Failure to do this can only result in the blockage becoming considerably worse.

Where the blockage is at the interceptor chamber, always rod through the cleaning eye rather than through the interceptor trap itself. The latter is best cleared by hand after the chamber has been emptied, using an old ladle or scoop. Be sure to use the plunger first; and when the blockage dislodges, flush and clean the chamber with water from a garden hose.

If the blockage is at the secondary chamber or in the pipework between this and the interceptor, rod towards the interceptor and flush through with plenty of water. When the secondary chamber starts to clear, move to the interceptor and rod this in the same way to remove the last traces of blocking material.

You may be working from a full or partially full chamber, which can be confusing as well as unpleasant because you cannot see the outlets. So make sure you are fully conversant with the layout of an inspection chamber before you start, and use the plunger attachment to ‘feel’ for the outlet. In some chambers, the outlets are flared or chuted to make this job easier, but in any case it is not as difficult as it sounds.

Should you at any time encounter a solid blockage which even the screw-head cannot shift, you would be well advised to call in expert help. It may well be that the drain has collapsed, in which case it must be given a smoke test to pinpoint the damage and then be excavated.

Gullies: If you notice backing up at an open gulley, the first thing to check is the inspection chamber into which it drains. If this is clear, the gully itself is probably blocked with debris and must be cleared out by hand. Only very rarely does the pipe between a gully and a chamber become blocked, and clearing it is a job which is best left to an expert. In Canada Instead of inspection chambers outside the houses, there is a main cleanout at the base of the soil stack in the basement, and beyond it a U-shaped house trap also fitted with cleanout eyes.

If there is a blockage in the main sewer line you can rod it clear with a hand or powered auger through either of these points.

You remove the cleanout eyes by unscrewing them with a large wrench: use penetrating oil if an eye is difficult to turn. Unscrew the eye very gently: if the blockage is beneath this point, all the waste that has blocked up from it will attempt to take this way out. Be prepared for the dirty water with mops and buckets.

Syphonage and compression

The design of household drainage systems is a complicated business about which there are strict rules. The most important of these specify sizes and maximum and minimun lengths for the discharge pipes joining outlets to the waste or soil stacks. More rules outline the correct slope or ‘fall’ for each type of discharge pipe and state where pipes can join the stacks in relation to one another.

Providing these design rules are obeyed, your drainage should function perfectly as long as it is not blocked. But all too frequently, badly planned drainage leaves a number of faults inherent in the system. These are often to be found in house extensions or in additions to the usual facilities such as bidets and showers. Syphonage: When the discharge pipe from an outlet is too small, too long, or of too steep a slope, waste water passing down it can create a vacuum and suck out the water in the trap beneath the unit. This is immediately noticeable as a gurgling noise when the outlet is drained, and may result in foul air entering the room because there is no longer a water seal to stop it.

Similar problems can occur if two discharge pipes are connected opposite each other at exactly the same point on the stack: water leaving one then sucks out the water in the trap at the top of the other.

The most obvious solution to the problem of syphonage is to dismantle the offending pipework and re-assemble it according to proper design rules. But this is not always feasible; if it were, it would probably have been done in the first place.

An alternative step, with a high chance of success, is to fit an anti-syphonage trap to the particular outlet. These units are made in a wide range of sizes to match the various types of conventional trap in existence, and they are fitted in exactly the same way. Compression: This is another symptom of a badly designed drainage system but it can also occur in complicated ai-rangements, even though the design requirements have been met. It is particularly common in one form or another on sub-stacks—the short downpipes that connect one or two outlets on a ground floor or extension to the main underground drains.

Compression is quite simply the build-up of abnormally high pressures somewhere in the discharge system, but it can manifest itself in a number of ways. For example, if a discharge enters the stack high up and another one enters lower down at the same time, the air between the two is compressed. This could result in one discharge ‘blowing back’ down the discharge pipe of another outlet—the reason why bath water can mysteriously appear in a downstairs shower. Alternatively the pressure may prevent the upper discharge from leaving the outlet at all—a condition which could last for several hours and mistakenly be taken for a blockage.

Always check for blockages first if you suspect compression problems: the condition sometimes arises artificially if there is less than full flow through the drains. Only when you are sure of the fault should you embark on the solution—fitting a vent pipe to the afflicted discharge pipe. Canadian above-ground drainage systems usually already have such revent pipes.

The vent pipe, which need only be 27mm wide, must be connected into the discharge pipe near the outlet end using a 45° ‘T’ connector. The angle of the connector must run against the flow of the drain, that is, upstream. From here, the pipe must rise vertically to above the spill-over level of the outlet.

Thereafter it can be run directly to the relevant discharge stack, to connect with it well above the highest existing connection. Or, if it is easier, it can fall again in a U shape and join the stack below the existing connections. In the first case, the horizontal run of the pipe should rise by about 18mm per metre. In the second, it should fall by the same degree.

The ease with which you can install a vent depends a great deal on the materials used for the discharge pipe and stack. Where these are both PVC, it is a relatively simple job. If either is metal, it is more difficult, and it may be better to replace the whole lot in PVC, particularly if the system needs repair in any case.

Air vents

All drains must be properly ventilated, or foul air rising from the chambers and stack will quickly make itself noticed. Whenever you can, inspect the terminals of waste and soil stacks where they emerge at roof level. Make sure that they are fitted with wire cages to prevent debris intruding and that the cages themselves are not blocked in any way.

In older drainage systems, a pipe often rises from each inspection chamber to a vent terminal at ground level. Inside the terminal is a simple valve which admits fresh air to the drain but prevents foul air escaping.

Unfortunately most such terminals are now in a poor state of repair and it is more than likely that the valves have ceased to function. If you find that the smell around a terminal is particularly unpleasant, the solution is to replace both terminal and valve with a modern PVC type or to buy a replacement breather valve to fit the existing terminal assembly.

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