A Complete Guide to Grey Water Reusal Systems
As you know, water is a precious resource. Thus, we should do our share in minimizing our use of water. One of the best ways to recycle water is through a system called the grey water reusal system. You can apply this system in your home and contribute to the water conservation efforts. Read on to find out more about this.
What is Grey Water?
So you must be wondering what grey water is. This basically refers to the used water coming from our bathroom sinks, tubs, washing machines, showers, etc. It should be noted that the water that can be used for this recycling system is “gently used” and has not gotten into contact with any fecal matter and other dangerous substances.
In case you didn’t know, almost a third of the water that we use daily goes to toilets, which gets into contact with the human wastes and is known as the black water. On the other hand, grey water is much easier to filter and recycle. Unlike the black water, it does not contain any fecal matter, as well as other bacteria and disease causing substances.
Grey water is dirty. It could contain traces of food, grease, dirt, hair and cleaning products. And although the water looks really dirty, it is safe and can be used for irrigation in your garden or yard. When it goes into lakes, rivers and seas, they end up as pollutants. But if you use them in irrigating your plants, they could serve as valuable fertilizer.
When it comes to this method of recycling, it is important to use products that are plant friendly. It should not contain salt, chlorine bleach and boron. The accumulation of boron and salts into the soil could end up damaging your plants. You must also be careful with using beauty products in the shower since some of these have harmful chemicals in them. If these chemicals will get into the grey water, they could end up causing harm to your plants during irrigation.
Aside from the benefit of minimizing the use of water, the grey water system can also help to lessen the volume of water that goes into your septic system, thus, reducing the risk of polluting the nearby water bodies. Using the system for irrigation also helps urban residents in minimizing the use of water for their backyard gardens.
There are various approaches when applying this system for irrigation but the best approach is to directly pipe it outside and feed to the fruit trees and ornamental plants. It can also be used safely in irrigating vegetable gardens, for as long as it will not get into contact with the part of the plants that will be eaten.
Aside from irrigation system, the recycled water can also be used for other purposes. It can also be used to wash clothes, flush the toilet and many more.
Grey Water Recycling
As mentioned above, this is the process of using wastewater from showers, baths, laundry and sink to feed plants or flush the toilet. However, it is important to remember that the water is definitely not safe for drinking, even if it has been treated. It can only be used for feeding the plants, washing clothes and flushing the toilets.
There are so many ways on how the grey water is treated, from the simplest method to the most complicated automated methods. The manner in which it will be treated will mainly depend on how you want the water to be used for.
- Using it to feed the plants – you can use the water directly without treating. But you should use it quickly because the bacteria that are present in water could feed from the organic matters present. Hence, they will end up multiplying fast. When the bacteria will use all the oxygen up, it will produce a foul smell and could end up harming your plants.
Using the grey water for plant feeding is pretty easy. You can directly syphon it from the sink or bath, or perhaps, you can install a valve into the external waste pipe to direct water towards the flowerbed.
- Biological systems that include food debris – grey water that contains food debris must be anaerobically treated with the use of a septic tank. The water that will go out of the end of the tank can be treated using soil box filter.
- Biological systems without any food debris – the initial process of filtering water that does not have any food debris is through sand filter, a process that will take out any large particles present. The grey water will then go towards the sand filter and will travel into the sand by means of gravity. The sand on the other hand, will take out any of the sizeable particles present.
- Mechanical filters for flushing toilets – the process of filtering the grey water for use in the toilet is easy. All you need is to undo the U-bend that’s below your sink in order to capture the wastewater from a bucket. You can then manually pour this towards the cistern. Although this method might be practical, this is quite time consuming.
If you do not want to go through the manual process of reusing water for toilet, you can purchase a device that will pump water away from various sources. This would include showers, sinks and tubs. When the water goes into the pump unit, it will pump water vertically to where it is needed. After which, the water will be treated in a tank before it will be sent into the cistern.
There are also several other mechanical filters that are a bit more expensive. One of these is the use of microfiltration systems that make use of membranes. If you have the budget for one, it can prove to be worth the additional investment.
What Can It Be Used For?
Two factors could affect the manner in which it can be used and these are the amount of water collected and its quality. Garden irrigation and toilet flushing are the most common ways the water is used although it can be used for several other things too.
A lot of people would use it for irrigating their trees, lawns, food crops and ornamentals. Although the method of irrigation in greenhouses will differ from the method of irrigating outdoors, similar guidelines can be followed in both situations.
- Apply into the soil directly instead of using a sprinkler or other methods that will expose the water into the outside elements.
- Do not use it for irrigating root crops and other plants that are often eaten uncooked.
- Do not use it to water plants that thrive in acid soil only.
- Use the water on plants that have already established and not on young plants and seedlings.
- Disperse the water into a large land area. Alternate in between fresh water to keep the sodium salts from building up.
When using the grey water to irrigate outdoors, it should only be applied on flat areas where runoff will not likely to happen. A cloth bag can be attached at the tip of the hose in order to help in the distribution of water, which will also act as additional filter. The filter must be removed and cleaned regularly which is ideally after every 3 – 4 days.
When used for flushing a toilet, a considerable amount of grey water can be possibly used. In fact, it accounts for as much as 50 percent of overall indoor water usage. If used for flushing toilets, poor quality of water is not going to be an issue. This is because it will go directly into the sewer and towards the septic tank.
It should be pumped directly into the toilet to be used for flushing the bowl. It should not be placed into the tank of the toilet because this could cause the flushing mechanism to get damaged. There is also a possibility that it will be back-siphoned to the supply of fresh water once the water pressure will suddenly decrease, which could affect the quality of your fresh water.
Grey water can also be added into ponds and lagoons to help grow the algae that can then be fed into the fishes on another pond. The algae can also be used as food for waterfowl and docks. The algae might have to be removed in order to keep it aerobic and to prevent bad odors.
The pond is then lined with stone, concrete or plastic in order to prevent the leakage of water. The system is an inexpensive and easy way of recycling water, although it may need the assistance of an expert to check the site before the lagoon is constructed.
The water can also be used in washing clothes through an automatic clothes washer and can be saved for the next batch of washing. When reusing the water for irrigation, avoid using fabric softener or detergent as these products may have harmful chemicals that could kill your plants. If the laundry includes soiled diapers, the water should not be reused for irrigation or for other purposes. Moreover, those that contain gasoline and diesel must only be reused for toilet flushing and not for irrigation or other purposes.
Difference Between Grey Water Vs. Black Water
We cannot go on with life without water. We need it to quench our thirst, prepare our food, clean ourselves, and many more. We basically need water in order to survive. The water that we use in our everyday activities ends up as wastewater. When washing dishes or taking a shower, the wastewater that’s produced gets collected into septic tanks.
The wastewater is divided in two categories – grey water and black water. These waters are kept in two separate tanks since they have different contamination levels and must therefore be treated and filtered differently. The wastewater can be recycled for use on irrigating plants, flushing toilets and washing clothes. The process of recycling consists of filtering, composting, distilling and other biological and mechanical treatment systems.
The black water is a type of wastewater that came from toilets and bathrooms and contains feces and urine. Also known as the brown water or sewage, the black water carries bacteria that could trigger diseases and is therefore harmful to our health. The black water can also refer to the water from flood, which is usually produced as a result of the overflowing of the bodies of water due to hurricane, heavy rain, typhoon, etc. This water combines with the sewage, and thus, it’s laded with bacteria.
When recycling the black water for fertilizer, it’s very important that it is processed well and decomposed properly in order to kill all the bacteria in it. During composting, heat is often used in order to kill the bacteria found in black water. These days, there are composting toilets available for use. In fact, several companies are already using them to help recycle their black water.
On the other hand, grey water is the kind of wastewater that comes from washing machines, sinks and tubs. They have much lesser contaminants compared to black water and therefore, they are much easier to treat, filter and process.
Grey water can in fact be used directly for irrigation on gardens, for as long as they do not have any harmful chemicals in them, such as detergents and soap that could possibly harm the soil. The recycled grey water is not only used for irrigation, but on wetlands as well. If it came from the sink, the food particles that go along with it could help to nourish the plants. The water can also be used for flushing toilets.
During the times of drought, recycling grey water is really useful. In fact, the water flowing from the sink and clothes washer can be heated for use again in bathing. Although there are those who though that recycling both grey water and black water could entice people to use more than conserve them, recycling wastewater is still good. This is especially true for those places where there is often a scarcity of water.
The public should be well educated and informed about the proper use of water and they must also be taught how to conserve and recycle it.
Systems for Homes
So as you know by now, grey water is basically a wastewater from your household that does not have any dangerous contaminants and can therefore be diverted safely for reuse, ether for landscape irrigation, toilet flushing, etc.
There are various advantages that come with using the residential grey water reusal system. First, you will have peace of mind at the thought that you will be reducing your footprint on Earth by minimizing your water consumption, as well as lessening the volume of water that will be municipally treated. Ideally, grey water is being used to irrigate plants. They are being treated separate from the black water, which contains harmful organisms. If you have an effective grey water system at home, you can help to significantly reduce your water use and end up saving hundreds on your utility bills each year.
There are two different configurations to choose from when it comes to the grey water systems for homes. The most effective water reuse for households is in watering trees and plants in the garden and landscape. Although there are now others who would use grey water indoors, it’s not highly advisable since the wastewater could trigger an excessive wear on your fixtures, such as your toilets. In addition, the use of grey water indoor is being subjected to the rigorous regulation of the government and the cost of permits, as well as the initial installation might just put off budget savvy homeowners.
Here are two of the grey water systems for home use that you may want to consider installing:
- Gravity Fed Grey Water Irrigation System – this type of system works by capturing the wastewater from your shower, sink or dishwasher. It will then filter it and send the water outdoors for irrigation. The trees and plants that will be watered for this system has to be at least three inches lower than the pipe used. This system does not require any plumbing modifications although it can also be possibly modified according to your preferences. In those states that allow for the reuse of grey water, a permit is no longer needed in order to operate the pump.
- Grey Water Irrigation Pump System – for watering landscapes and gardens that have different elevations or those with complicated layouts and have an extensive amount of space, the grey water irrigation pump system can be used. It is available in different surge configurations and pumping capacity. It can be directly plumbed to catch the wastewater coming from your sink, shower and washing machine. The wastewater is then filtered by the filter system of the pump before it goes out to be used for drip irrigation in the garden.
If you are going to use most of the grey water for irrigating the plants in your garden or landscape, it is therefore important that you avoid using products that could harm your plants. When showering, avoid using detergents, shampoo and soap that contain harmful chemicals and bleach. Most of the plantings could survive in water with some soap, but this is not the case for smaller plantings and seedlings.
Grey Water Systems Cost
The overall cost of getting the grey water reusal systems installed will greatly vary depending on how simple or complicated its plumbing mechanisms are. Other factors that could affect the cost would be the size of the yard for irrigation and who will perform the installation.
Much of the work required for the simple installation of a grey water reusal system is digging. This will include digging the trenches and the mulch basins where the pipes are to be buried. If you are trying to save money and you think you are capable of digging using your own tools, then you can go ahead and dig yourself. This will save you money on the labor cost. Another option is to ask friends and family to help out with the digging. That way, the labor cost for your grey water system installation will somehow be lessened.
Below is a rough estimate of the cost of grey water systems. Again, the cost will greatly vary depending on the complexity of the installation and how big the site is:
Wastewater from laundry to landscape irrigation:
- Materials – $100 to $250
- Full installation – $700 to $2,000
Branched drain system:
- Materials – $200 to $400
- Full installation – $800 to $3,000
Pumped system installation:
- Materials – $400 to $600
- Full installation – $1,000 to $4,000
Installation of automated pumped system for use on landscape drip irritation:
- High-end residential installation – $5,000 to $20,000
The figures mentioned are only for the initial installation costs. There are several other factors that must be taken into consideration in the overall cost of using the grey water reusal system at home. A new system may also include several operating costs, like the service contracts with the providers and manufacturers, energy costs, as well as the cost of asset maintenance, such as the repair and replacement of pumps, etc.
Depending on the system you have chosen to install, the cost of installation might cost you some serious money. But the savings and convenience that you get to enjoy once the system starts operating is definitely worth it. Savings include the sewer and water rate savings that are often based on your local agency charges, the incentives from government and utility agencies, as well as tax deductions.
If the main sewer line in your local area is capable of accommodating your new system and that there is no longer a need to upsize or do any infrastructure upgrade, there will surely be great savings that you can get out of the installation of a grey water reusal system. Of course, there’s also the green factor benefit that could result in the minimal use of natural resources for operating your house, as well as the decrease in utility costs.
Ultimately, the more water you end up recycling, the shorter the return on investment on your grey water system will be. This method of recycling water has become such a desirable investment in the market now because of its effective water conservation efforts, as well as its potential to offset the increase of future water rates. Although the grey water system for water reuse may not be applicable for all households, they should definitely be given serious consideration since it could potentially lead to a long-term savings on utility.
Grey Water Filter
The government has been serious about its effort in conserving water. Thus, water conservation has become a growing concern all over the world these days. If you want to contribute in your own ways, consider building a grey water filter. The process is easy and will not cost you a lot of money.
Before you begin, you must first prepare the materials needed. You will need a 5-gallon bucket or any capacity that you prefer. Next, you will need pea gravel, terry cloths, charcoal, lint-free cloth, dish detergent, pipe connectors, pond filter, sand, electric drill, sponge and another bucket for collecting water. Once you have all the materials ready, you can now begin with the task.
- Clean your bucket prior to using – pour several drops of dishwashing detergent into the bucket and run warm water until halfway up. Grab a sponge and dip it into the soapy water. Use it to clean the sides of the bucket and rinse it well with water. Make sure there are no remaining suds and leave it to dry completely. You can also choose to wipe it dry using a lint-free piece of cloth.
- Create holes on the bucket – drill about 1 1/2-inch of holes at the bottom of the bucket. You will use a pipe connector for the drainage port. However, it must first be modified before attaching. So drill several holes at one end of the connector. Insert it into the hole of the bucket, with the drilled area facing up.
- Create the filter system – now that the bucket and drainage system is ready, you can go ahead and start creating your grey water filter. Wash thoroughly the pea gravel in order to rinse any residue off and all other dirt in it. Dry the gravel before using. Once dry, fill the bottom part of the bucket with as much gravel as you can, or until such time that it is leveled with the pipe connector.
- Place a cloth above the gravel – to provide extra filtration, place terry cloth on top of the gravel. This also helps in the easy cleaning of the filter. Then grab the pond filters and cut it in the same size as that of the bucket. Place it inside the bucket and grab another terry cloth and place it above the filter. The extra cloth will help to prevent the gravel from getting inside the filter.
- Add more sand – add up to four inches thick of sand into the bucket. Place another cloth above the sand and then place the pond filter right above the cloth. Place another cloth above the filter thereafter.
- Add charcoal – for those who wanted to produce drinkable water, consider adding two layers of crushed charcoal. Place the first layer of the charcoal above the gravel and then the second layer should be played on top of the sand.
So now that you are done with building your grey water filter, you can go ahead and start using it. Simply pour wastewater into the bucket. Wait for a few moments until such time that the water will be able to pass through the various layers and get filtered. With the use of the collector bucket, catch the water that goes out of the filter. You can then boil the water for use in washing the dishes and clothes.
As you can see, the process of creating your own filter at home is easy. Sure, it might require a lot of time, but once you start using it, you will realize that all your time and effort will be well worth it.
Portable Grey Water Tanks
If you are fond of camping using your RV or recreational vehicle, then you sure know that you will end up generating plenty of wastewater at the campsite. Disposing the wastewater can be such a pain. If you will camp on those camping grounds that have sewer hookups, then disposing the wastewater should not be a problem. However, if you will camp on other places, then you might have to make use of a portable water tank to collect the water.
As you already know by now, there are two kinds of wastewater. One is the black water and another is the grey water. Black water, as you know, is a type of sewage that contains lots of harmful bacteria. On the other hand, grey water is the wastewater that’s gently used and often comes from the shower, tub, sinks and laundry, provided that biodegradable soaps are used.
In some places, wastewater that have come from the sink where food is being cleared off the pots, plates, utensils and pans before wash, belongs to the grey water category. There are places however that have strict regulations where any water coming from the kitchen sink is not considered grey, but black.
In some camping grounds, disposal of the grey water to the ground is permitted, as long as the area is far from the shrubs, trees, plants, etc. Most places however will prohibit the disposal of grey water into the ground. In this case, you need to make use of the tank system in collecting your wastewater.
There are several different types of tank systems that you can use for the collection of the grey water. Recreational vehicles, large trailers, motor homes and campers would make use of three different types of tanks for their wastewater disposal, and these are the following:
- Fresh water tank
- Grey water tank – water coming from the kitchen sink
- Black water tank – water from the toilet
Most of the tent trailers will only carry with them fresh water tank. Bigger units will have self-contained water tank for black water, while a few of them have built-in grey water tank.
Regardless of the type of tank you will use and your strategy for the water disposal, it’s important to keep in mind that one gallon of water is equivalent to 8.33 pounds. Thus, if you are going to use a water tank that has a capacity of 10 gallons, then you can expect for it to weigh more than 80 pounds. And remember, it will not take that long for your 10-gallon tank to be filled especially if you have to shower often.
Most of the camping grounds that do not have any sewer hook-ups will usually have a sanitary dump near the place. Thus, a lot of trailer owners will end up using those grey water totes that they can wheel into the nearby dump station as soon as they get full. This tote could accommodate as much as 30 gallons of water and comes with a handle that can be easily hooked up into the trailer.
When looking for grey water tanks, make sure that you choose something durable. It should be made from first grade plastic material and comes with warranty. There are several tanks that you can find in the market. Aside from being used as grey water storage, these tanks are also used for other purposes, such as rainwater harvesting, temporary storage of contaminated water, and many more.
Grey Water Disposal
By now, you have already understood the concept of grey water and the importance of reusing wastewater. As you know, there are various means in which you can dispose the water in order to be reused at home. According to the EPA, or the Environmental Protection Agency of the US, a typical American family is said to be using as much as 400 galloons of water every single day. Thus, if you will choose to repurpose the water that goes to waste each day, then you sure could save a lot of money in your utility bills.A typical American family is said to be using as much as 400 galloons of water every single day Click To Tweet
Again, you can dispose the wastewater in different ways. First is the simple solution:
- Get in touch with your local city department and inquire about the regulations concerning the disposal of grey water. This is because these local ordinances might limit your means of disposing the wastewater.
- Next, think of how much you can afford for the grey water disposal. Although most solutions are not that expensive to implement, it will be to your advantage if you can decide ahead of time how much you can actually afford for this system. Depending on the method you will use, you might have to pay a professional for the consultation and installation and this could add up to the overall cost as well.
- To begin with, grab a bucket and place it in your bathroom to collect the wastewater from your shower, tub, laundry and sink.
- Use the accumulated wastewater in feeding the plants in your garden or lawn. For as long as you will immediately use the water on that same day that you have collected them, you should not have any issues with it. The water should still be free from any harmful bacteria.
- Do not ever leave the water to stay longer in the bucket because the bacteria and other germs could eventually grow in it.
Another method of disposing the grey water would be to dispose it from your laundry room then into the garden:
- Consider the installation of a grey water reusal system that will automatically divert water from your laundry area directly into your outdoor landscaping. The process will require drilling a hole at the exterior wall of your house, on the area that’s beside your laundry room in order to accommodate the drainage pipe. The pipe usually comes attached with a hose that will be used in watering your garden. You can also install a three-way valve in order to control the flow of water.
- Next, bury the hose under the soil or mulch in order for it not to be exposed in your garden. This is also to provide for the safer delivery of the wastewater towards your plants. You can also choose to hide the hose underneath the paving stones, if you have them in your lawn. The amount of space and the type of cover that you will be using should also be based on your local government’s regulations.
- Make sure that you examine the laundry products that you will use for washing clothes before you decide to divert the wastewater into your landscaping or garden. Some of these products may have bleach and sodium in them that are harmful to the plants. You can use liquid detergent instead of powder in order to avoid the accumulation of sodium in water.
Another method is to collect water from your sinks towards your plant irrigation in the garden:
- Build a household solution that will capture all the grey water that goes out of your lavatory sinks. This method will require the assistance of a professional in order to avoid any health issues that are associated with the contaminants found in the grey water.
- Use a filtration system that can filter the sediments and debris from the wastewater. You may add a treatment solution to make this process even more effective.
- Again, make sure that you closely examine the products you use in your sinks as these may have some harmful chemicals in them, making them not suitable for use in your garden irrigation.
DIY Grey Water Systems
It is a common knowledge that reusing water can greatly save energy. The grey water system is the best way to recycle water for household use. Aside from saving money on your utilities, the system can also help to lessen the pressure on the scarcity of water resources especially on the drier areas of the country, where several households are often faced with the scarcity of water supply. To give you an idea, here are some DIY grey water systems that you can follow at home.
- Use of dishpan or bucket – the simplest method is to collect the accumulated wastewater into a dishpan or bucket. The water could come from the hand washed dishes and clothes. After you have collected enough water, simply toss the wastewater directly into your flowerbed and fruit trees. This is the easiest and the most inexpensive way to reuse grey water for irrigation. It does not require much effort and will definitely not cost you anything.
- Laundry to landscape system – another easy and popular system to reuse water is the landscape direct system, which diverts the grey water from the washing machine directly into your garden or landscape. The water can first be collected in a mulch basin surrounding the bushes and trees. This system will capture the accumulated grey water from the washing machine’s hose and then send it directly into your plants through the tubing that’s about an inch in diameter. This is a great system since it will not require the need to alter any of the existing plumbing in your laundry. For a horizontal axis washing machine, you can expect to harvest up to 25 gallons for every load of washing. If you have a vertical axis washing machine, you could collect as much as 40 gallons.
- Use diverter valve – you can also install a diverter valve into your washing machine in order to easily divert water. You can then strategically position and attach the hose, then dig a mulch basin for your vegetation. The mulch basin will provide for enough room for the grey water to be able to spread out all over the plants while also preventing any runoff of water. This also helps to prevent pools of water where mosquitoes could breed. Furthermore, the mulch also prevents the soap and grease from clogging your garden soil. This system should cost you less than $200 only, which is way cheaper than hiring professionals for the installation. In fact, you can spend as much as $2,000 for the professional installation of a grey water system. This can work well in irrigating bushes, trees, perennials and large annuals.
There are several other grey water system options that you can build by yourself. These systems should be easy for you if you are knowledgeable with basic landscaping and plumbing. There are also plumbers who are familiar with the use of grey water system for irrigation and can help you out. They can also install diverter valve for you for a minimal fee. Otherwise, consider hiring a professional landscape that has wide experience in the grey water system for irrigation.
How to Build a Grey Water Pit
The process of treating grey water is really easy. Perhaps, what’s difficult is in configuring the plumbing in order for the pipe to be able to carry water to the place where you want it to be. If you are building a pit for your grey water, here are the steps to guide you through.
- You will be using a kiddie pool for this DIY project. So begin by setting the pool at the ground. Use a garden hose in tracing the shape of the pool. An 8-foot kiddie pool should be enough to provide you with enough supply of grey water for your daily consumption.
- Next, dig a hole that’s similar to the shape and size of the kiddie pool. Basically, the pool should be able to sit flatly into the ground, within the hole.
- Grab a hacksaw and cut a notch that’s about 2 by 2 inches on the area of the pool where you want the water to be able to flow through.
- Use the hacksaw to cut the bottom of a five-gallon bucket. Cut a hole in the bucket, that’s also about 2 by 2 inches in size. The pipe that will be carrying the grey water towards your garden or landscape is going to be mounted into this notch.
- Next, cut another notch that’s about 3 by 3 inches in size at the top rim of the bucket and then set the bucket into the pool, where the rim side down is on the opposite side from where the notch has been cut. These holes can help the grey water to be able to freely flow out into the bottom.
- Inside the pool, place equal layers of cobblestones, coarse gravel, fine gravel, pebbles and coarse grit. The finest substance should be placed above the progressively bigger rocks down below. On the other hand, the bucket should be surrounded completely with stones, where only the top few inches is sticking up. However, it should not end up having any stones right within it.
- Position the outlet of the pipe of the grey water into the upper notch of the bucket and then place a piece of flagstone right above the bucket. It will act as a lid.
- You can now plant your wetland species into the pebbles at the surface of the pool, making sure that they are spaced out a foot apart from each other.
- Dig about 8 inches deep of trench that’s also about 20 feet long and fill it with as many wooden chips as you can in order to soak the water that has flown out. The wooden chips will decompose slowly and can be used as soil amendment and must be replaced at least once a year.
- If preferred, the flagstones can be placed at the edge of the pool in order to conceal the pool’s plastic rim.
Your grey water pit is now ready to receive wastewater. After about two days of use, the water will begin overflowing off the hole that was cut right at the rim of the kiddie pool. Another option is to place a second pool below the hole that has been left free from gravel and is used as water feature. The good thing about installing another pool is that it can serve as holding area of the grey water that you will use for irrigating your landscape or garden. This would still need to have a trench filled with mulch that can overflow into the downhill side.