Considering carbon neutrality from water in buildings

Wet areas and drainage systems

Whether a house or workplace, there are always wet areas in our daily life for defecation, hand washing, etc. They are essential to maintain a sanitary environment in buildings.

The basic components of water facilities are a water supply facility that distributes water to buildings, a plumbing fixture that uses water, and a drainage system that discharges used water out of the building. In addition, there are various systems such as a hot water supply facility to supply hot water and a facility to filter rainwater, etc. to make the water quality usable in buildings.

These systems are collectively called plumbing systems.

Many of these systems have developed remarkably in recent years with the aim of improving functions and saving energy, water, etc.

However, drainage systems have not changed fundamentally since about 200 years ago. It is a mechanism to slope the piping installed in the building and discharge sewage by gravity.

In other words, water used in kitchens, baths, washbasins, and toilets is drained through piping installed so that it gradually flows down toward the outside of the premises.

The natural flow driven by gravity may seem a bit primitive, but it is the ultimate ecosystem in the sense that it can transport waste and water without the use of electricity or other forms of energy.

Drainage of buildings that obstruct reformation

In recent years, however, this drainage system has become a problem in some cases.

Today, it is said to be the era of the 100-year life. Life stages change greatly, so the way of living changes accordingly, and it becomes necessary to remodel dwelling houses. However, the drainage system often becomes a problem when remodeling the wet areas in apartments.

In many old apartment buildings, the direct flooring method is used, where floor materials are laid directly on concrete slabs, which serve as the skeleton structure. In order to install piping, the wet areas were raised one step higher. That is why the wet areas of old apartment building have steps and are not barrier-free.

On the other hand, in modern apartment buildings, the double floor method is common, where short pillars are erected on slabs and finishing floors such as flooring are constructed. The piping and wiring are installed between the double floors.

At that time, the slope of drain pipes and the pipe diameter tend to be a problem. The reason for this is that while water supply pipes and hot water supply pipes have a pipe diameter of 13 to 20 mm, drainage pipe diameter is more than doubled because inner drainage pipe is composed of two layers, a drainage layer and a ventilation layer, in addition, a drainage pipe is required gradient. Therefore, the height of the double floor where the drain pipe is installed must be secured, for example, by further lowering the slab in that area.

As a result, the water facilities are laid out together in one area, often planned near the location of the drain stack pipe to which drain pipes are connected.

Then, for example, when the life stage changes and the needs of home care for elderly people increase, it is difficult to install wet areas in the desired place even if we try to install more toilets and washbasins because we cannot install drain pipes in the rooms that are not originally designed to install wet areas.

In other words, it is said to be the era of the 100-year life, and the changes in the layout of dwelling houses are required, but it is difficult to cope with this with the conventional drainage system.

Extra drainage system to evolve conventional drainage systems

So, what kind of measures are there? One answer is the extra drainage system I am researching.

In short, the extra drainage system is a general term for a drainage system which enables drain pipes to have a small diameter with no gradient (or gentle gradient).

As an example of a small-diameter drain pipe, the diameter of a washing machine drain can be drastically reduced to 20 to 25 mm in the extra drainage system, compared to 50 mm in the conventional drain system.

At present, the extra drainage system is roughly divided into a method using pumps and a method using the siphonage.

In a familiar example, a pump is a machine used to transport water when the remaining bath water is used in a washing machine. The extra drainage system uses slightly larger pumps.

The methods which use pumps include the small pumping drainage system and the vacuum drainage system. The small pumping drainage system uses a pressure pump to pump up and transport water, while the vacuum drainage system uses a vacuum pump to pump up and transport water.

In this system, the degree of freedom of drain pipes is quite high, and it is possible to place wet areas anywhere you like. The pipe diameter can be reduced and pipes can be installed under the roof by using pumps instead of under the floor.

However, it is important to understand that it consumes a small amount of energy because it requires electric power to operate pumps compared to the conventional drainage system that uses gradients.

The extra drainage system also has the siphonic drainage system.

This is an application of the siphonage. Water can flow as long as the last point of outflow is lower than the point of inflow of the sanitary equipment regardless of the height of the piping between the two points. With this principle, pipes under the floor can be installed without a gradient.

The required condition is that the drain flows down in the drain pipe in full stream and connects to the drain stack pipe, which is the discharge destination on each floor.

Therefore, there are some restrictions, such as the need to design the part that connects the water from the plumbing fixtures to the drainage stack lower than the normal level, but the siphonic drainage system is an ecosystem just like the conventional drainage system because it does not use electricity.

In this way, the extra drainage system is a system that allows water to flow regardless of the slope of the pipes, which gives you a higher degree of freedom in building design.

Since the reconstruction of a building consumes a lot of resources and energy, it is important to use a building for a long time. The extra drainage system makes it easy to renovate houses according to the life stage of the residents and contributes to the realization of long-life houses, resource saving and energy saving.

Considering carbon neutrality from water in buildings

The goal of achieving carbon neutrality by 2050 has been set globally, and further energy saving and water and hot water saving are required. In Japan, ZEH (Net Zero Energy House) for houses and ZEB (Net Zero Energy Building), which reduces the net energy consumption in buildings to zero by energy creation technologies and energy saving technologies, which reduces the energy consumption in the buildings, are strongly recommended for building performance.

Most of the energy used in buildings mainly consists of that consumed by air-conditioning equipment such as air conditioners and ventilation fans, and electrical equipment such as lighting and elevators. Also, plumbing systems consume energy. For this reason, I am reconsidering the conventional water supply design materials and methods as research that leads to water-saving and energy-saving water supplies in buildings.

Water saving measures for sanitary equipment, such as water-saving toilets, automatic faucets, and air-in-showers, have made significant progress since the 1990s, while design materials for water supply facilities has remained unchanged since the 1980s. If the design materials remain outdated, it will not be possible to reflect the water saving measures in the sanitary equipment, and the pumps to transfer water and water tanks to store water will become excessive. Therefore, it is an urgent task to update these outdated design materials.

For example, as a basis for planning, a facility designer may use the water supply unit, which is the daily water consumption per person or per bed, for approximate planning. According to the current design standards of general hospitals, the daily water supply unit is 1,500 to 3,500 L/bed. However, surveys and analyses of actual conditions based on actual measurements and literature have shown that the amount of water actually required is less than half of that.

By setting detailed design standards that are appropriate for the actual situation, designers can optimize pumps and pipe diameters to reduce the energy consumption of pumps and other devices, which has been excessive until now, and to reduce the energy consumed in the manufacture of pipes.

In addition, we can save water and energy through facility improvement such as using solar heat as energy for hot water supply and using collected and filtered rainwater and dew condensation water from air conditioning as recycled water for cleaning toilets and other miscellaneous purposes to reduce the amount of tap water, which is filtered in water treatment plants.

Each of these improvements is small, but by accumulating them, we can reduce energy consumption throughout the lifecycle of buildings, from design and construction to operation and demolition, thereby reducing CO₂ emissions and contributing to carbon neutrality.

We will continue to cherish people, buildings, water, and the earth so that all of them can coexist in harmony. We conduct research every day to achieve this goal and improve the technology.

* The information contained herein is current as of February 2023.
* The contents of articles on Meiji.net are based on the personal ideas and opinions of the author and do not indicate the official opinion of Meiji University.
* I work to achieve SDGs related to the educational and research themes that I am currently engaged in.

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