drains@dalrod.co.uk 0845 22 37 112

There are currently over 75 skyscrapers in the UK, with thousands of employees or residence occupying these buildings and producing waste. But on the internal structure, of some of these most impressive looking buildings, is a very complex drainage system. Thousands of people flush the toilet, run water in a sink do not realising how the waste gets from the top to the bottom of buildings that span over 310m high.

In buildings over 5 floors, waste will rocket down pipes at a speed of 122mph, which is the equivalent to the average speed of most mainline trains in the UK. Waste hits the terminal velocity (highest point it falls) – just like a skydiver. Pipes are normally made from PVC – but in bigger buildings, particularly in London, at least the bottom section of the stack is cast iron to protect from rats, fire and the sheer pressure of waste flowing down them. Most tall buildings in the UK require a second pipe running alongside the main one to allow air to flow – and bad smells to escape from the top of the building.

Next thing to think about is the use the facilities in the building are likely to receive – for example, office toilets are used less than those in hotels. A formula is used to find out how many litres per second of liquid you can expect to get rid of down the toilet system, which in turn tells you the size of waste pipe that will be needed. An example of a 10 storey domestic building would require a 125mm diameter pipe compared to a domestic 4 bedroom home it would be 110mm.

Waste does bounce back up at the bottom, in order to minimise bounceback of waste from pipes running down many storeys of buildings, the bottom of the ‘stack’ – the main vertical pipe that carries waste – has to be at a certain radius, specified by British Standards.

This allows the flow of waste to follow a bend and then flow horizontally and into a drain, where the flow decreases – this is known as a hydraulic jump. This is affected by the initial speed and amount of liquid flowing, as well as the location of pipes leading from toilets into the main stack.

In certain circumstances, a pumping station is needed to filter the amount of waste through the building in the case of the Shard there is 3 pumping stations to control the waste through the tallest building in the UK.

So if you visit the Shard or any other large skyscraper and use the facilities, just remember the journey your waste will take to get down to the bottom to the main sewer lines.

If you require advice about your commercial buildings drainage system, don’t hesitate to give the experts DALROD a call on 0845 22 37 112.