A reflective white roof is more effective than lawn for greening existing buildings, here is a link to my article published on LinkedIn https://t.co/H8SyyavhHU
The first time you open the hot tap or your shower you have to wait some time for hot water to arrive, during that waiting time the unwanted cold or tepid water is lost to the drain, obviously this occurs because the water inside the water pipe, between the water heater and tap is cold (the deadleg).
To reduce that waste water, the length of dead leg (green) should be as short as possible, for a 22 mm pipe, every linear metre of pipe contains about 0.32 litres of cold water.
In extreme cases the dead leg could be 10 metres in length, that equates to approx. 3.2 litres of waste water every day, or 1168 litres per year wasted.
Now that might not seem to be huge amount of water, but if you multiply that by 3,000,000 households in Hong Kong, you get the idea.
In Hong Kong apartments the length of hot water dead leg pipe is typically quite short because individual water heaters are mainly used, but not always. Presently there is no legislation in Hong Kong governing the maximum length of the hot water dead leg, whereas overseas in United kingdom for example, it is specified.
This photo nicely demonstrates the position of two water mains underground exposed by construction, the deepest water main is barely 250 mm below grade. Because it is shallow, close to the surface, that means 1) it can be easily damaged, and 2) cold water is not kept cold, due to warm soil temperatures in summer.
Considering the water quality delivered to the tap, it is no wonder that Hong Kong people prefer bottled water, and boil water everyday.
Whilst the quality of our drinking water provided by our water utility (WSD) may reach world class standards, what comes out of the tap is a different matter. Improved plumbing systems, piping, tanks, coupled with mandatory maintenance are required to rebuild the confidence to use the potable water provided, learn more here. In my office the water (see photo above) is very poor indeed, would you drink it? And boiling all that water demands a lot energy, we are looking at approx. 9.28 MW everyday just to boil water.
Typically one main water storage water tank is provided in high rise buildings with thousands of residents. The building owner or operator may opt for a voluntary scheme, operated by WSD, known as the Quality Water Recognition Scheme for Buildings (QWRSB). Of course, that requires interrupting the occupants water service to conduct the necessary maintenance and tank cleansing work.
by John A. Herbert
Hong Kong, a diesel truck coasts along the fast lane of the highway (near MegaBox) to water the plants. It was a hot day, so spraying (misting) water into the air helps it evaporate easily wasting water.
At the same time the opportunity to use rainwater from the highway directly above is loss because it is piped and needlessly dumped into the common sewer system (Hong Kong has a single sewer and storm water sewerage system), there is a better way!
This is best practice in Hong Kong, a diesel truck hauls water for irrigation of the streetscape. In this case, filmed at Murray road by the AIA building in Central, the truck sits with its engine idling, but not all of the water actually reaches the plants, water is pouring out from the truck bed on to the road surface.
Another variation, the diesel truck cruises the streets at a low speed, with a helper hosing down the plants (Wang Hoi Road, Kowloon Bay, Hong Kong).
If you are really unlucky, one watering truck route meanders along blocking the only lane from Kowloon west leading into the Central/Hunghom tunnel.
For more than 50 years seawater has been used for toilet and urinal flushing in Hong Kong, saving significantly quantity of fresh water. If you are near the coast, the process is straightforward, sea water is filtered, treated and then pumped to purpose built service reservoirs ready for use in residual and commercial buildings. Eighty percent of Hong Kong buildings are served by the sea water infrastructure. In the year 2011, the potable water savings were 740 tonnes per day, or more than 270,000 tonnes per year.
All new buildings by regulation mustbe provided with two separate water systems, potable and flushing water. The flushing water infrastructure must be designed to handle sea water. in buildings uPVC is the material of choice for pipework serving all sanitary appliances. WC cisterns are designed without any metal components exposed to the corrosive seawater.
Underground the pipework distribution utilises cement lined piping for sea water to the service reservoirs and buildings as shown in the above diagram (courtesy of Hong Kong Water Supplies Dept. https://www.whittonplumbing.com/24-hour-emergency-service/).
Having separate potable and sea water infrastructure has another advantage, in the event that one water service is shut-down for maintenance, that doesn’t stop all the water services. Furthermore, since the sea water provides part of the buildings water demand, the potable infrastructure is smaller and lower cost.
One of the major objections against using sea water is a concern that potable water and seawater piping could be cross-connected, in reality that’s an unlikely occurrence because the materials are different, its physically difficult to connect a cement lined pipe to PE piping.
Its obvious really, in coastal areas, why flush our precious potable fresh water down the toilet? The use of sea water is a low-tech solution to lower and conserve potable water usage, and very cost effective.
Update: John Herbert was appointed to the Hong Kong Green Building Council Faculty June 2012 and chairs the Water Aspects technical group.
Buildings demand a significant use of our finite resources including fuel for energy usage, water consumption, and cause atmospheric and environmental impacts from waste. Our pace of consumption cannot be maintained if some natural resources are to be spared, we need to build smarter, its crucial for our sustainability if tomorrow’s child is to be left with some usable resources.
The Green Building concept aims to reduce the environmental impact of new and existing buildings, yet environmental impact of buildings is often underestimated, a recent survey show people though buildings had little or no impact on the environment! whereas the scary fact is that 63% of Hong Kong’s Carbon footprint results from its buildings.
Some green labelling systems such as BEAM address part of the problem, but its only voluntary system. However building labelling and sustainability requires more science, including the entire life cycle impacts being assessed.
Sadly, the availability of fresh water is a critical, life threatening issue for many regions, yet developed countries, including Hong Kong frequently waste water. The photograph above shows a typical Hong Kong “Irrigation system”, a diesel fuel water tanker truck and manual hose, water efficiency is clearly not important. In this system most the water is lost in the spray, evaporation to atmosphere, or wetting the adjacent paving. Hong Kong is not alone in this regard, it occurs elsewhere, but that is not an excuse. Its a practice that needs to be stopped to avert water security and shortfall nightmares.
Water efficient alternatives exist, sub-soil irrigation avoids the short-comings delivering water into the root systems without evapouration losses, and excess.
— John Herbert, consultant, Kelcroft E&M Limited