Most people know that having an effective gutter system is essential. It protects not just your property but the environment around it. But where does rainwater go once it enters your downpipe? Knowing where your gutter should drain to is important – and could save you money.
This guide looks at the crucial role played by the humble downpipe, gullies and adopted sewers. And, no, a downspout should not allow water to pour straight into the ground at the base of a wall. The role of the downspout is to channel water either into a public drainage system or, at least, away from the immediate environs of your property. Drainage of rainwater is strictly controlled, and you should not install a drain yourself without checking regulations. Note: controls can vary so make sure you make enquiries with the relevant local authority.
While some downpipes discharge rainwater onto the land, this is only done when they are connected to pipes that extend around four feet away from a structure. Downpipes that simply let water soak into the soil close to your home will cause damp and other serious issues. With weather events becoming increasingly common and more severe, it makes sense to ensure your gutter system and associated drainage is up to the job. Without adequate drainage, your gutters will be a waste of time.
Most homes in the UK send water from a gutter drain to a sewer system operated by a water company. But, to get there, the surface water has to first leave your guttering. When rainwater exits your downpipe, it should enter a gully. This is nearly always level with the ground. Most gullies used in the UK are manufactured with a bend. You may not know this, because the bend is out of sight. It is buried below ground. This is simply to prevent odours. Modern gullies are made from PVC. However, in older properties, you may find a gully manufactured from a type of clay.
Gullies have different profiles, depending on their drainage function. For example, a back-inlet gully will allow a downpipe to discharge rainwater below the ground level. Some homes may have a French drain. This is a method used by some building contractors to transfer surface water into the garden. However, we do not recommend you connect a downpipe to one of these drains unless it is well away from your home. This will require the installation of underground pipes. To check whether you have a French drain, look for signs of a gravel-filled trench. And never undertake any work without ensuring you have the necessary consent.
The collection and processing of most rainwater is the responsibility of water companies, once it has safely exited your gutter system. Nationally, the cost of dealing with domestic surface water is more than £1billion a year – cash recouped through water bills. If you are not sure if your surface water ends up in a public drainage system, check your bill. It should state whether or not you are being charged for surface water drainage. If you can’t see it specifically mentioned, take the time to find out what the sewer or standing charge includes. Properties that use a soakaway system, for example, should not have to pay this additional charge - and homeowners not sending surface water to a sewer are entitled to claim a rebate. Visit your local water company’s website to see what you may be entitled to claim back.
Private surface water systems can be found in some properties, especially older homes and those in rural or remote locations. In these cases, rainwater is collected by the gutter system, sent to the downpipe, then a gully and most often onto a soakaway. There are restrictions on where soakaways can be installed, because they can allow contaminants to penetrate the groundwater table.
The soakaway has been a common way to remove surface water from properties not on the sewer system for many years. Advancements in construction methods have made them better at coping with larger quantities of rainwater. Today’s soakaways benefit from rings made from concrete to enhance their capacity and make them more efficient. Early examples comprised a crude hole cut into the soil and filled with debris, often bricks. One of the advantages was that the common brick eventually degrades and forms a non-porous layer.
Contemporary soakaways are slightly more sophisticated. They benefit from broken up concrete and pieces of flintstone. The soakaway can be constructed to exactly meet the needs of a property and its location. People connected to a public sewer may invest in a soakaway if they want to protect a prized lawn or keep water away from a large garden structure where the gutter system is not connected to a sewer.
Note: You are unlikely to be able to claim a rebate if you have a soakaway in addition to being connected to a public sewer. Here is some useful information on Building Regulations relating to drainage.
Understanding how your guttering works and where it diverts surface water to is important. For example, if you are replacing a downpipe connected to a soakaway, you will need to ensure underground piping is at least four or five feet away from your property. Make sure you inspect downpipes and gullies regularly to ensure they do not become blocked or clogged with debris. The last thing you want is an overflowing gulley and water seeping into the ground around your home.
If you want to know which drain your surface water enters, you can inspect a map of public sewers. It will detail, all local sewers. The maps are free to view, and you can usually make arrangements to see them via your local authority. It is worth knowing where drains are if you are planning to extend your home. Any increase in the size of a roof should take into account additional loads on the gutter and drainage system.