Dealing with misconnected drains

Figuring out drains and misconnections involves a bit of fact checking and following basic design. But it is vitally needed: a UK Water Industry report suggests around 140,000 properties – and in some areas up to one in five properties – are misconnected. The nationwide total could be more than 500,000.

There are two main types of sewer: separate systems and combined systems. The combined system does exactly that, both foul and rain water are in one pipe whereas separate systems have two pipes. Foul (wastewater) systems carry water from waste pipes and toilets, while surface-water sewers carry rainwater that has come down from guttering and driveways and discharges into rivers and the sea.

Misconnections most commonly happen when work is carried out to extend or modernise a property, or when a new washing machine or dishwasher is plumbed into the household system.

If the new plumbing wrongly drains to a surface-water sewer then the effluent will pollute local rivers, which is not only bad for the environment but also a legal issue. Equally, if clean-water drains are not connected properly, they could overflow and cause flooding.

There are simple fixes that can sort these problems out – as long as you know where to look. Follow these steps to help resolve issues.

1 Work out when the property was built.

In most houses built after 1920, wastewater drains into separate sewer systems (foul sewers and surface-water sewers). In this kind of system, clean rainwater runs away to a surface-water sewer, which drains straight into local rivers and streams. The other simple way to recognise what you have is that a separate system will also have two manhole covers close by each other (one trench was dug to fit both pipes hence they are mostly side by side), these are generally found at boundaries and at any change of direction, e.g. going to the side or rear of a property.

If the property dates before 1920, it will most likely have ‘combined’ drainage that goes directly to a sewerage works.

2 Drains are laid, in most cases, as point to point when the building was built and run in as straight a line as possible. This is because to discharge the contents they require not only gradient but minimum changes of direction so they don’t have the potential to block.

3 The system will have access points at a change of direction or a junction in the form of a manhole or inspection chamber. These are generally heavy and jammed in over many years of being compressed in older properties and might require specialist equipment to lift them. Modern properties will probably have plastic pipes and manholes etc. However, if you are going to start lifting manhole covers then beware that they could be really heavy. Some are concrete and they can easily trap fingers or toes, or worst case drop inside the drain if you don’t know what you are doing. Until you lift a manhole you don’t know just how deep they might be and some are very deep. On top of this you should consider others around you, if you start to lift manholes and leave holes for someone to fall into, e.g. the homeowner or visitors. They will be assuming that the environment they are used to walking around is safe! This type of inspection isn’t a DIY job and requires risk assessing as well as safety equipment and probably more than one person.

4 When tracing water in a drainage system a dye is used. This allows the thorough inspection to check for leakage, direction and cross connections as the bright dye will show up far easier than water being flushed.

5 Main sewers are generally located in the road, even here you can quickly spot the number of manholes side by side if it’s a separate system. This is the property of the local authority and must not be tampered with. These are the starting point and the deepest point. As the connection is brought into the property, the pipes beneath will have a gradient and generally head as the crow flies. Cross connections occur when additional work is done at what is known as the head of the drain – the top or the furthest point.

6 Has the building been altered in any way since it was built? If there is an extension or if a new bathroom or kitchen has been installed in a new location, you will need to check if it has been installed correctly to the nearest suitable pipe. This is especially important for macerator toilets as these are often wrongly installed into surface drains causing pollution. Cross connections occur when additional work is done at what is known as the head of the drain (the top or furthest point). The drains need to be covered with earth after installation and finished off with either grass or some sort of paving if it’s a public area. If the existing system is already at the highest point then extending it is a bigger job and this is where short cuts start to creep in and things go badly wrong.

7 Plot the guttering pipes. Look at all exterior guttering downpipes to see if there have been any new connections from inside the property that should be sewerage pipes. It’s not uncommon to see a washbasin or shower added into a room and the waste pipe cut into the rain water pipe outside simply because this was for them the nearest pipe!

8 Outside toilets and utility rooms, including domestic garages converted into rooms, can also cause problems as they are frequently connected to water drains as a quick fix.

Drainage systems and alterations in most cases come under Building Control and ought to have been inspected at the time. However, building extensions below 3m (4m on detached properties) are not subject to inspection so cross connections can be more commonly found.

Cross connections are a breach of the Building Regulations Part H and G5 sanitation and create contamination. Drinking water is taken from rivers and streams in some areas. If a cross connection is discharging effluent into this then it becomes a very serious public health hazard.

The basic rules are: trace the steps that have been taken by the previous installer. Waste pipes must go to foul drains and not rainwater pipes or guttering.

Buyer beware: the legal responsibility

– It’s the homeowner’s responsibility to ensure there are no misconnections at their property.

– The homeowner is also responsible for pipework on their property up to where it joins the public sewer.

This article first appeared in the Jan/Feb 2020 issue of P&H Engineering, the magazine for members of the CIPHE. Find out how to join here.

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