BUILDING BRIEFING:

Drainage

To understand the problems of the drainage system it is essential to know how drainage has evolved and the particular areas within the system where failure can occur.

Prior to the 19th Century Public Health Acts, drainage was often simply the ejection of waste into an open gully in the street.  A cesspool in the garden (for those properties that had a garden) with a 'privy' above became an alternative.

As a result of the Public Health Acts, local authorities were made responsible for the disposal of all waste material, and a network of below ground drains were developed, often extending into the sea for discharge.  Although we may still use the same pipework, the use of sewerage treatment works has radically altered the basis of disposal.

However, the Property Manager, other than understanding that the majority of properties drain into a public system, need not concern himself with this, as any responsibilities relating to it lie with the relevant local or water authority/company.

All modern property is built with a two-type drainage system whereby rainwater and foul water are dealt with separately.  The diagram overleaf shows a typical two-pipe system.  However, in many cases both pipes will still drain into the same public system, and it is therefore feasible that foul smells can come from the rainwater system.

The use of 'P', 'S' and 'V' traps/bends attached to the WC, bidet, hand basin, sink, bath, shower etc. should prevent smells emitting from the apparatus. In each case the trap retains a level of water which stops smells being transmitted through.  They can become blocked with waste material, but are usually readily accessible and can be cleared by physical or chemical means.

Foul drainage

The standard problems with foul drainage are:

1.     Blockage.

2.     Cracked pipe.

3.     Broken seal.

4.     Loss of water in trap.

Considering each in turn, a blockage can occur because the fall of the pipe does not give an adequate flow, waste therefore stabilises in the pipe and, over a period of time, blocks further waste flow, as the majority of solid waste flows along the bottom of the pipe.  To ensure an adequate flow a 100 mm waste pipe must have a fall of at least 1 in 40.

A cracked pipe below ground can also result in material from the surrounding ground invading the pipe and be the source of the blockage.  Alternatively, a crack or a cracked seal can result in smells invading the surrounding area, as both will allow the foul air in the pipe to escape.

The loss of water in the trap will, obviously, allow the foul air to pass through the trap.  But how can the water be lost?  Normally regular use, assuming no damage to the trap, will keep the water level at the required level.  However, in dry weather the water can evaporate if the system is not used for an extensive period.

Avoiding action

Regular inspections will minimise the potential problems.  The checklist should include:

1.     Lift any accessible manhole covers to ensure free flow when running a tap or flushing the WC.

2.     Check all brackets holding waste pipes to the wall, ensuring no movement of the pipes.

3.     Check all seals between the various lengths of pipe to ensure they are tight and not cracked.

4.     Ensure that all traps are filled with water.

5.     Consider any protection to exposed pipes to avoid accidental collision that may causing cracking.

6.     Check that some form of vent cover is in place at the head of the soil vent pipe to avoid birds nesting, or debris such as leaves entering the pipe.

Rainwater drainage

These checks, in the main, also apply to the rainwater goods.  But, due to the open nature of gutters and hoppers, there is an additional problem with blockages causing rainwater to pour over the edge of the gutter or hopper, thereby causing a potential damp problem within the property.  Blockages can be caused by leaves, slipped tiles/slates, or as examples, a ball or dead bird.  A regular ladder-based check of the gutter is therefore essential, particularly in the autumn in areas where deciduous trees abound.

Calling on the experts

When appointing a contractor to carry out any work on drainage, ensure they are suitably qualified. Various television programmes and a recent consumer report have highlighted the high prices and poor workmanship carried out by rogue traders, so personal recommendations are a good place to start.

There are a few other specific matters of which the Property Manager should be aware.

Macerators

These are mainly used where a normal piped system would not have the correct fall.  A good example of this is the basement flat where the mains drainage outside is at a higher level than the WC in the flat.  The macerator liquidises the solid waste and pumps it up into the drainage system.  The main problem with macerators is their inability to cope with a large amount of solid waste.  Tenants should be advised so that large amounts of toilet paper or sanitary towels are not put into the system.

Septic tanks and cesspools

In some rural areas homes are not connected to mains drainage, and septic tanks or cesspools (cesspits) are used.  Originally a brick, stone or concrete box, modern ones are plastic, and all are buried near the property they serve.  They collect all waste from the household drains, but a septic tank works like a simple sewage treatment works by separating solids from liquid, which can then soak away.

A cesspool is simply a container that must be regularly emptied, every week in some cases.  Modern versions may be emptied less frequently - perhaps 10 times per year.  Septic tanks also require 'de-sludging' at least once a year.

The most likely problem with older installations is lack of capacity – our water usage for washing clothes, dishes and ourselves has increased considerably over the years.   An average family house should have a septic tank system with a total holding capacity of approximately 1000 gallons.

Potential problems

When a septic tank or its soakaway does not function properly it can cause odour nuisance, flooding and pollution, and it may be determined a statutory nuisance under Section 79 of the Environmental Protection Act 1990.  A notice may be served requiring the person responsible for the septic tank to ensure that any nuisance is removed.

If the system is not effectively separating solids from liquids then the effluent leaving the septic tank will in time tend to clog the soakaway, which reduces the permeability of the soil and an excess of sewage in the system will result.  This will build up in the drainage pipes and manholes and/or may rise above the soakaway and breakout onto the surface.

To rectify the problem the tank should be de-sludged, and the soakaway may need a jet clean, by a suitable contractor.  It is possible that some repair work to the soakaway may be required.  Prevention is far better than cure, and it is most important that a septic tank is emptied at least once a year.

In an ideal world with some anaerobic biological action, a good crust layer, regular emptying and adequately vented drainage pipe work a septic tank should not smell.  However, it is not uncommon to get the occasional unpleasant odour, and fitting airtight access covers may resolve the issue.

Prevention

For a landlord or agent, the most important instructions to give tenants are about the care that must be taken with what is introduced into a septic tank: Fats, oils or heavy grease, paints, solvents and motor oils, garden chemicals and pesticides should not be put down the drain.  Nappies, plastic or sanitary items, should not be disposed of into the system.

• In addition, to avoid problems, the property manager must ensure:
• The size of the tank is sufficient;
• The septic tank is properly maintained and emptied regularly;
• The septic tank access lids are secure and in good working order; and
• The drains to and from the septic tank, including the soakaway, are free-flowing and free from blockages.

In conclusion, if the property manager has a basic understanding of how the drainage systems operate for the properties he manages, he will be able to advise his tenants (and landlords) accordingly and, thus, avoid some of the more obvious pitfalls (eg blocked drains), as well as be in a position to act promptly and from a base of knowledge if there are drainage problems during a let.