Why Underground Drainage?
Not only are the right tools and products very important in the installation of underground drainage but the knowledge and skills too. Whilst it isn’t a complicated task, making mistakes could lead to a lot of damage and consequently you may find yourselves in trouble with the local Building Control Department.
Building Control Department
The department must be contacted before starting any work on underground drainage, whether it be installing new drainage or adapting what is already there. However, if it is a damaged or broken part of your underground drainage, you may fix without permission. It is always best to double check though and you can give them a call on 020 7091 6860.
There are two types of drainage systems, as you may already know. The foul water which is all waste from, toilets, baths, kitchen sinks, dishwashers and washing machines; any sewage or grey waste water. And the surface water – this is rainwater only.
In some older properties, often the wastewater and surface water will run into the foul water pipes. This is okay, however you will need to ensure that a trapped gully is installed so that no foul air escapes. It is considered best and standard practice when the foul and surface water run into their separate drainage systems.
Installing Underground Drainage
Planning – The first step is extremely important, you must have a clear plan, where everything will go, how it’s going to connect up and does it adhere to regulations. A diagram can be very useful. You must ensure the underground drainage does not interfere with the foundations of your home or building. You can secure the blueprints of your property from the local council.
Trenches – Building Regulations state that the top of the pipes must be at least 300m deeper than ground level. There should be a bed of pea shingles or something similar to provide stability for your drainage.
Laying & Connecting – the actual setting down of the pipes correctly is very important. The gradient of the pipes has to be correct to ensure the waste and surface water flows properly. For instance the minimum gradient requirements for foul water drainage the minimum requirement is 1:40 (if a toilet is connected it should be 1:80) with a 25mm height fall per metre and for surface water drainage is 1:100 and 10mm fall in height per metre of run. When the pipes need to pass through a building wall, there will need to be a lintel with a clearance of at least 50mm around the pipes. The hole will need to be covered with a rigid sheet to ensure vermin and soil do not end up in your home.
Maintenance – PVC pipes are prone to wear and tear over a number of years. This means that from time to time you could be required to carry out some maintenance procedure. Manholes, gullies and chambers should all be installed at accessible points, this way you can clear any blockages, rod the pipework or access any other parts that may need repair work.
Inspection – As already mentioned, the building control department has to be aware of your work, when the work is complete they should be called to carry out an inspection and they can grant you a certification of approval.
Equipment & Drainage Products
As with most building products, there are a great many suppliers and merchants where you can purchase the products and tools you will need for your projects.
For the purpose of this guide, we will be looking at Allflo; www.allflo.co.uk
The reasons for which this type of drainage is so revolutionary to the market are listed below:
100% uPVC; (unplasticised polyvinyl chloride) a chemically resistant form of PVC. So, what are the advantages of uPVC pipe over against PVC pipes? Whilst PVC pipe is easier to cut into smaller pieces, can be fastened with glue and is used largely in the US to replace copper and aluminium pipes in irrigation and pool circulation systems, the uPVC pipe proves to be one of the most beneficial types of plastic pipe in the world, due to its incredible resistance to chemical erosion, it’s smoother inner walls that help water flow and it’s functionality in a wide range of temperatures and operating pressures.
British kite-marked and BBA approved; it’s very important that the quality and safety of a product is tested and approved by the British Standards Institute and the British Board of Agreement. Allflo has both certificates. The British kite-mark on Allflo drainage is to EN1401.
Ease of Installation; Allflo is manufactured with the ease of installation in mind, we’ve had feedback from construction professionals and ground workers telling us of the difficulties of fitting the pipes together, the damages if the pipes are not fitted together correctly or are forced together when trying to install. Allflo drainage has a double seal injection moulded cap on all of its fittings. When trying to fit the pipe with only a single seal cap, it could be very likely that the seal will end up folded back on itself, causing it to fail the air test. The double seal means that there is extra support there, the second lip acting as a back-up for the first.
The pipe chamfer tool; This chamfer tool is becoming widely used and recognized as the safer and more efficient way to square and chamfer 110m plastic pipe. It fits on to your drill and is very easy to use: https://snsbp.co.uk/shop/110mm-pipe-chamfering-tool/
Lubricant Gel; It is very important that nothing other than the dedicated lubricant gel for underground drainage is used, should an alternate or other gel be used, the consequences could be leaking and unnecessary damage.
Please check out our construction guide on soakaway systems here: https://snsbp.co.uk/soakaway-crates/