Top 5 Components of a Commercial Greywater Irrigation System


Published: March 16, 2022 | by Wahaso Water Harvesting Solutions

Top 5 Components of a Commercial Greywater Irrigation System

Greywater is the term used to describe gently used water from sinks, showers, and laundry systems. While blackwater—wastewater that has come into contact with feces — is typically treated by municipal wastewater systems, greywater can be recycled on-site for irrigation, cooling towers, toilet flushing, and other non-potable applications. A greywater irrigation system is valuable for any business or organization looking to reduce its water bill and eco-footprint. It can also serve as a backup water source in drought or municipal water shortages. This invaluable system uses water from greywater sources to irrigate landscaping, reuse in a cooling tower, flush toilets, and in many other applications. The system collects water from sinks, showers, and washing machines for toilets, irrigation, and cooling towers instead of buying water from the local municipality. It diverts water from greywater sources like shower drains and washing machine hoses to a holding tank. The system pumps water through a filtration system and stores it for future use.

1. Greywater Collection

The first step in creating a greywater irrigation system is to collect the greywater. This can be done with a simple diversion valve that diverts water from the drainpipe to a holding tank. We place the valve at the point where water enters the building so that all greywater can be collected.

Here are a few areas where you can collect greywater:

  • Shower drains – Perfect for hotels and other businesses with large numbers of guests. The industry uses a lot of water for showers, which can make a big difference. The average hotel guest uses 100 gallons per day during their stay. This doesn’t include water use in public areas, restaurants, bars, and other guest services.
  • Washing machines – Laundry is another water-intensive activity, making washing machine greywater a perfect candidate for reuse. According to Danamark, the average commercial laundry machine uses 2.5 to 3.5 gallons of water per pound of laundry and handles between 25 to 400 pounds per load.
    Sinks – Sinks are another prominent place to collect greywater. When you look at the number of sinks in a building, it adds up quickly. Handwashing, brushing teeth, and shaving are all activities that use water that can be reused.

Designing a commercial greywater irrigation system requires careful planning and consideration of many factors, but there are five critical components to every commercial greywater irrigation system:


2. Filtration

The first step in recycling greywater is to filter it. The two-part system ensures complete filtration before the water goes into a holding tank. It includes a pre-filter and an ultra-filtration membrane or secondary filter.

  • Pre-Filter:
    The pre-filter protects the ultra-filtration membrane by removing large particles like hair and lint that could clog it. This process also removes any suspended solids in the water that could settle and create odors in the storage tank.
  • Ultra-Filtration Membrane:
    The ultra-filtration membrane is a high-quality filter that removes 99.9% of all particles larger than 0.02 microns. This step is vital to protect downstream components like irrigation systems from being clogged by small particles. This membrane creates incredibly pure water.

3. Storage

Many options exist for storing greywater, from rain barrels to underground storage tanks. The size and type of storage tank you’ll need depends on how much greywater your facility produces and how you plan to use it. A common rule of thumb is that each person uses about 75 gallons of greywater daily. When used for flushing toilets, for example, a greywater system cistern can be quite small while still saving 100s of thousands of gallons a day because as soon as the water is made available from sinks and showers, it is just as quickly used to flush toilets. A storage tank that’s too small will fill up quickly and lead to overflows, while a tank that’s too large will be expensive offer a diminishing return on its size. Be sure also to consider future needs when working with your manufacturer and design partners to size a storage tank for your facility. When you schedule a free consultation, we can help you determine the best type of storage tank for your facility. We’ll also help you decide the size and quantity of storage tanks you’ll need to meet your greywater needs.

4. Sanitation and Pumping

Once the greywater is sanitized through an ultra-filtration membrane or other sanitizing technology, it is pumped to its designated use, such as irrigation nozzles, toilets, or in cooling towers. We must adequately size the pump to ensure that the greywater is delivered to its ultimate destination at the appropriate pressure and flow rate.

5. End Use for the water

The last step is to put the greywater to use. It can be used for irrigation, flushing toilets, or cooling towers.

  • Irrigation:
    Irrigation is one of the most common uses for greywater. It helps reduce water waste and provides clean water for plants.
  • Toilet Flushing:
    Flushing toilets is another everyday use for greywater. It’s a great way to reduce water waste and save money on your water bill. A typically residential building can provide 125% of its toilet flushing demand with greywater.
  • Cooling Towers:
    Cooling towers are a great way to use greywater. These systems use the cooling effect of evaporating water to supplement a building’s cooling. Cooling towers often use millions of gallons of water per year.

Greywater harvesting is a great way to reduce water consumption and save money on monthly bills. We can help you design a custom commercial greywater irrigation system that meets your needs.

We offer a free consultation and feasibility service to help determine the best design for your facility and how much water you can save. Once a design is finalized we build and furnish complete systems that we commission and warranty.

Contact us for a Free Estimate.


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