Water Use, Treatment and Conservation Considerations in Construction
Summer is an appropriate time of year to talk about water and water conservation. This is the time of year that we start to experience drought conditions, and our water supplies, during some summers, start to diminish, forcing some communities to regulate water use with the banning of lawn watering and car washing. It is also the time of year when we see some of the most devastating storms and the flooding they cause.
The three aspects of water we’ll address are water conservation, water treatment and disposal, and water reuse and storm water management. By reducing our water use we can also reduce the water flowing out that has to be treated at the sewer plant.
The first place to look to reduce our water use is our plumbing fixtures, toilets, faucets, and shower heads.
A typical toilet that was installed ten plus years ago used five-seven gallons of water per flush. The regulated standard for a new toilet is 1.6 gallons per flush. This can be reduced to one gallon or less per flush on some models. A new class of toilet, which is gaining popularity, is the dual flush toilet, which offer a reduced flush for liquids and paper only, and a regular flush for solids. A toilet which uses no water is a composting toilet. These toilets use biological decomposition to break down the waste into a few buckets of humus per year. A composting toilet is expensive compared to a standard flush toilet, but that cost may be offset by the reduced need for a standard septic system, and is certainly an integral part of a water-conserving waste water system.
The next biggest water user is showers. Water conserving shower heads should use less than 2.5 gallons per minute, and that can be reduced to less than 1.5 gallons per minute with some of the most efficient models. Also don’t forget when we reduce our shower flow rate, we are also reducing hot water use so we’re saving energy as well, which brings up another area of water use, waiting for the hot water to reach the point of use. Most plumbing supply systems, in a new home, use a manifold distribution system, which incorporates a separate water line to each fixture. This type of water delivery system allows for reduced water pipe diameter, which reduces the amount of water that is standing by to be delivered to the shower. Another technology to reduce the standby hot water use is to install a hot water loop, regulated by a circulator and a thermostat.
Aerators are a very inexpensive way to reduce water flow and can usually be added to existing shower heads and faucets. Valves with easy to operate levers can be helpful to turn water on and off while using the bathroom and kitchen sinks.
Another big water user is the clothes washer. The new front-loading washers use at least half as much water as a top-loading washer. These new washers also extract more water during the spin cycle which helps save energy during drying.
Waste water is a concern because of the cost of treatment and the environmental impact of discharging the treated water into our streams and rivers. Some municipalities have systems that have waste water and storm water in the same pipe system, causing the treatment plants to be overwhelmed during a large rain storm. Another byproduct from the treatment plant is the residual solid waste. This waste is spread on farm fields or sent to landfills. There is concern that this waste may contain certain pollutants. If you cannot connect to the public system, you have to build an on site septic system.
One alternative method to deal with waste water is a grey wastewater system. With this system there are two sewer drainpipe systems, one for the toilets, (black water), and one for the showers and sinks. There are many variations on grey water reuse, but typically it is collected, filtered, and dispersed to an irrigation system. One model of a grey water irrigation system is a constructed wetland. With this system, the grey water flows through specific soils and plants designed to absorb and filter the grey water after which it can be used for additional irrigation or discharged.
Another technology for dealing with waste water is called a “Living Machine.” A living machine is more sophisticated than the constructed wetland in that it uses more biological organisms, including some types of snails and fish, to breakdown and digest the pollutants. The treated water can then be reused to flush toilets, in irrigation systems or discharged. Because of cost and operating consideration, these systems are more suited for office buildings or as a residential community system.
A very simple and practical way to save water is with rain water harvesting. Ancient civilizations used this basic method for collecting water for irrigation. A modern system in our climate can reuse the rain water for flushing toilets, washing cars, irrigation, and with a proper filtering system, washing clothes and showering. The system would collect the rain water off the roof and direct it into a cistern. The first water off the roof during a storm, which would contain particulates and pollutants, would be flushed out before entering the cistern. The cistern would be designed and sized to meet the needs of the intended use and to match the average rainfall. A pump system, or gravity, would then work to direct the water to its intended use.
Rainwater harvesting is also an integral part of a storm water management system, which is a requirement in almost all new construction projects in this part of Pennsylvania. Another way to reduce storm water runoff is to reduce the impervious surface of the project by reducing the size of roadways, driveways and parking areas and by using alternative products, such as porous paving and pavers, to allow the rain water to penetrate back into the ground. ‘Rain gardens’ are one of the latest design ideas in storm water management. A rain garden incorporates retention and infiltration along with intensive planting to absorb and evaporate water back into the atmosphere, to mimic the natural way undeveloped land would deal with rain water and runoff.
Other topics to be addressed in this series will include energy, heating and cooling, lighting, building materials, indoor air and environment and solar power.