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- London’s Shard pumps water higher than any other building in Europe.
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- The Burj Khalifa is the world’s tallest skyscraper, at 830 metres.
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- Water towers have been replaced by a system of mid-level pumps and valves.
That’s not the most staggering statistic about it though. Do you know how much sewage will be flowing out of it when it’s fully occupied? Thirty-six litres per second. 129,600 litres of foul discharge per hour. That is 3.1 million litres per day.
Just how does a building cope with so much waste and water? Join us as we walk you through extreme plumbing 101: getting water to heights you never thought possible.
Getting it up
Shunting water up to the top of a skyscraper is no mean feat: gravity takes its toll on a free flowing liquid. The higher you need to send it, the more pressure you’ll need, and the tougher the pipes to take that force.
“You have to try and keep the water pressures down as much as possible if you can,” Christopher Moore, senior engineer at Arup, who designed the water system for the Shard, tells Humans Invent.
For an eight-storey building, you’d be looking at a pressure of around nine or ten Bars in the pipe. But start going above that and it creeps up: high rise buildings can easily require pipe pressures above 16 Bar, and at this point standard piping can fail.
By floor 55, you’re looking at a pressure of 25 Bars. You don’t want that. “Above 25 Bar, you start struggling to find pipework and valves that have got approval for use because it’s so high pressure,” says Moore.
“It becomes little dangerous. There’s kind of a worry about things failing. At that pressure, they can fail quite catastrophically.” A metal things exploding at speed and killing you sort of fail, in other words.
So what’s the solution? A series of pumps and tanks that act as staging levels for the water, and feed H2O gently down to the floors below them. The Shard for instance has five tanks in total that can store 159,000 litres of potable cold water, and 19 pumps serving it up.
Pump rooms on floors 20, 51 and 68 reset the pressure, so there are just a few storeys where the pressure goes higher than the industry maximum 16 Bar – and yet it delivers water up to the 87th floor, 283 metres above ground, a first anywhere in Europe.
Simple right? Except the real estate on a skyscraper is at a premium: the higher you go, the more you can charge a City banker to live there. That then leads to clashes with the designers, and the developers.
“Architects never like pump rooms to be above ground, but obviously we have to force them into plant rooms in some prime area, halfway up a building or in penthouse areas,” says Moore. “You’ve got great views from the plant rooms!”
And getting it down again
What goes up must come down, but though you’re looking at water plummeting down hundreds of metres, it’s actually not that different to dealing with waste water in your own home. Liquid travels down a pipe in a spiral motion, and hits terminal velocity pretty quickly.
“You’ll get it in two or three floors: in a low rise building you’re already dealing with terminal velocity,” says Moore.
There’s an extra factor to deal with though: smell. As drainage sloshes down, it draws air down with it. Suddenly, you’re looking at a huge amount of air pressure at the bottom of the building, and a very real possibility of it being expelled out of sinks, vents, toilets, you name it. If you don’t use two separate drainage systems, your residents will be able to tell/smell.
“As it gets to the bottom, all that air suddenly has nowhere to go and there’s a massive positive pressure,” says Moore. “In a high rise building it becomes much much worse. You have to drain the bottom few floors separately, otherwise the positive pressure would be blasting the smell and pressure out through the lowest fittings.”
Going green
Plumbing a skyscraper is as much about pragmatism as it is about physics: juggling the needs of architects, developers, and the people who end up living and working there, all while trying to meet standards, which are becoming increasingly energy efficient – Part L of current British buildings regulations is dedicated to fuel efficiency and insulation.
“As a public health engineer dealing with water, there’s a lot of drive towards with water efficiency, which goes hand in hand with energy efficiency,” says Moore. “In an apartment, you try and comply with the code for sustainable homes which is trying to reduce the volume of water use per person per day.”
In a skyscraper, it’s easy to make the bathroom fittings in office floors use less water, but low water use fittings might not have been what the architect had in mind when he was mocking up designs for the penthouses at the top of the tower, with luxurious vistas and power showers.
“You talk to the architect, you say that you’ve got to use a low flow shower, low flow fittings. That can be quite difficult on a high end building. Modern luxury apartments are having to provide fairly low flow fittings.”
And that’s before you factor other blinging displays of wealth into the equation.
“In the Middle East there’s less requirement for sustainable design. They’re a bit behind us there,” says Moore. “They do do things like say, ‘Oh, we’ll put a big swimming pool on the roof’, and we’ll say, ‘oh, it’s not very sustainable’.”
That’s an understatement: rooftop pools can lose millions and millions of litres of water a year just through evaporation.
What’s next?
Water efficiency is important now, but it’s only going to become more vital as the planet heats up, and modern skyscraper designs are starting to reflect that.
“I think we’re going to see a lot more in terms of water conservation and water re-use,” says Robert Sedlak, senior vice-president for plumbing at New York engineering firm WSP Flack and Kurtz, which oversaw the systems for Kuala Lumpur’s 452 metre Petronas Towers.
Sedlak’s firm already uses rain water harvesting in skyscrapers where it can, and is now investigating reusing grey water from bathrooms and laundry, for say, air conditioning. That alone could save a small fortune: the world’s tallest building, the 830 metre Burj Khalifa in Dubai, uses 21 miles of piping for aircon alone.
The next step though? On-site sewage plants, says Sedlak. WSP Flack and Kurtz has already put up two buildings which can recycle water within the building, and he thinks it could become standard in the near future.
Variable speed inverters on pumps meanwhile allow you to regulate the amount of water served up while keeping pressure constant, and have been available for a few decades. They can save as much as 30 percent in energy and water usage according to Xylem, which provides the pumps for the Burj Khalifa. But even these could be replaced in future, by something unexpected: sprinkler systems on a large scale.
“I could see them being used in high rise buildings. You can pump two different pressures off the same pump, if for example you didn’t have space for a mid-level plant room and you had to go fairly high pressure,” says Moore.
“You could run 10 bar off one side of it and 20 bar off the other side of it. I don’t think anyone’s thought about trying it, because generally they’re manufactured by specialised sprinkler makers.”
Typically with construction, you can think big, but only if you’ve got the money. Green is important now, but in time it may make economic sense to switch to these new systems too.
“There’s speculation that water is going to be an expensive commodity at some point,” concludes Sedlak. “Right now it’s not cost effective for doing that, but as the price goes up it will become cost effective.”
Image credits:
Shard: Sellar Group
