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FREQUENTLY ASKED QUESTIONS ABOUT RAINWATER & GREYWATER HARVESTING
I have an existing building that I would like to make “greener”. Can I install a rainwater harvesting system? What about a greywater system?
In existing buildings, it can be relatively inexpensive to capture rainwater coming from rooftop downspouts into a storage tank to use for irrigation or cooling tower make-up. Consider cooling condensate as another readily accessible source of harvested water in existing buildings. Storage can be handled in either underground or above-ground tanks.
Flushing toilets with harvested water creates more issues in existing buildings (see second point below). The cost of adding greywater harvesting systems to an existing building is considerably greater than with new construction. Using harvested water to flush toilets requires a supply line separate from potable water servicing sinks in the bathrooms. And to harvest greywater, waste lines from showers and sinks must be separate from the toilet waste stream. This extra plumbing is prohibitively expensive to install in an existing building unless the building is being gutted. But every building is different, and greywater harvesting may be practical in some situations.
How do I decide which type of system or systems is best for my building?
Every building situation is unique – particularly with the availability and usage needs for harvested water. Considerations include:
- The type of building and usage – offices vs. residential
- Availability of greywater from showers, sinks, washing machines
- Rain frequency and amounts in your area
- Number of toilets and number of building occupants
- Land use around the building – amount of landscaping, type of parking facility and stormwater runoff,
What is the value of water harvesting in LEED Certification?
Water harvesting efforts can earn 10-12 points across a number of LEED categories including;
- Conserving water
- Reducing energy consumption
- Reducing the depletion of natural resources and materials
- Creating a sustainable site
- Use of innovative design
What are the considerations of using harvested greywater for a building?
An efficient greywater system first requires a steady source of greywater. The most abundant source is showers in buildings with full time residents – dormitories, hotels, schools, etc. Restaurants with heavy dishwashing or clothes washing use may also produce suitable quantities to support greywater harvesting. Office buildings generally do not produce enough usable greywater to warrant the cost of a system.
When there is an abundant supply of greywater, it can be a more reliable source of water for flushing toilets than rainwater. The amount of shower and sink usage generally ties to the amount of toilet use in a building, so there is almost always a balance in supply and demand for greywater.
Greywater harvesting requires additional treatment versus rainwater. This is due to the heavier load of soaps and organic particles that are carried in greywater. The additional filtering and sterilization requirements can add 50% to the cost of a system vs. rainwater harvesting systems.
Can harvested greywater be used for irrigation?
Yes – the quality of water after treatment delivers near-potability making the water completely safe for irrigating lawns and landscaping – even for spray irrigation systems. Local codes can be confusing on this matter. Technically, greywater is untreated water from showers and sinks, and many communities have strict codes regarding use of untreated greywater. Our systems convert greywater to On Site Treated Non-Potable Water, and the implications for usage are different – so a careful check of local ordinances is important.
When greywater is used to flush toilets, is there any color or odor? Are there any special requirements for cleaning toilets or handling odors?
The filtering and disinfecting processes used by Water Harvesting Solutions eliminates any odor or color in the greywater delivered to toilets. We add steps to bring the water to near-potable quality so that there are no additional cleaning or odor handling systems required.
Our community makes reclaimed water (municipally treated sewer water) available for irrigation. Can that water be used to flush toilets in our building?
This is a great idea that should be more common than it is – and depends on the regulations in your community. Reclaimed water often has issues with odor that may be unacceptable for toilet use; a filtering step can be applied to eliminate any remaining odors or colors in the reclaimed water. Local ordinances in your area may regulate the use of reclaimed water to flush toilets.
Do you provide ongoing system maintenance services?
Yes. We can support your own maintenance team with training or arrange a local service company for any routine maintenance.
What additional operating costs are associated with active systems?
Depending on the type of system installed, sanitation chemicals and filter elements will need to be periodically replaced.
What is the typical payback for a Water Harvesting system? Do they make economical sense?
System payback depends on a number of factors including the type of system installed (and its cost), the cost of municipal water, the local fees for water discharged into the waste system, environmental impact fees for storm water management, etc.
Payback is only one of many considerations for installing a water harvesting system. This can range from 5-15 years depending on your circumstances. Most clients also have broader interests in supporting sustainability of potable water for their area; water harvesting is usually one of several actions taken by clients in an overall environmentally sensitive building.more complicated systems.
What funding opportunities are there for harvesting systems?
We are hearing more about grants and other funding resources all the time for projects that reduce water use or reduce the impact of stormwater on the watershed.