Gray Water Harvest System


A Gray Water Harvest system that collects, re-uses and processes grey-water from the tiny-house to decrease tap water use, generate savings and decrease water waste. It would also dechlorinate and enrich tap water to avoid damaging soil life and therefore increase fertility. This system would also help in decreasing labor by eliminating the need for direct irrigation in some of our gardens.


This Survey uses the data from the Client Interview and the Site Survey.

Current site elements

As it can be seen on the Overall Site Survey and on the diagram below, the main building on this 0.5acre lot is a 35’ by 35’ concrete structure. This building is divided into 4 apartments which are rented short term. All drain pipes join on the back of the house (westernmost side) below the soil level. From this main drain pipe, only the last 2 feet are accessible. The rest runs under a concrete floor. All of the main building apartments’ gray water, drains at this point.

The detached building in the main diagram (Zone 0- Tiny House), is an 8’ x 20’ tiny house, which is occupied by one to two persons at a time. From this building, the kitchen and bathroom drain pipes come out through the western-outer wall of the house at a 2 to 3 feet height from the outside floor (See diagram below). At this residence, only Eco-friendly products are used.

Next to the tiny-house, two sections of the “Zone 1 Garden” are located, (Garden 1 and 2) as it can be seen in the diagram above. For more information on the Zone 1 Garden design, you can visit its design’s web page.

The open space to the west of the tiny house, which is around 13” by 7”, is roofed and is only occupied by our washer machine. A 4 feet tall concrete fence is located to the west of this area and marks the edge of the lot. To the west of this concrete fence, a small creek runs which is dry for most of the year.

Types of waste

Grey-water generated from the tiny house is controllable because this is my main residence and is used by Ms. Ortiz when I’m deployed to the U.S. All products used in this house are eco-friendly products which include Dr Bronners, for almost everything (Shower, Shampoo, dishwashing, etc.). For surface cleaning, we use vinegar and/or alcohol.

Dishes are pre-wiped so food scraps are never released down the drain because they are placed in the compost heap or the vermi-compost basin (5- Composting System and 6-Vermiculture System). Also, our main diet does not include fried foods or any animal products.

Needs and Wants related to this system

As it can be seen in the Client interview, the main purpose of this design is to lower water waste and the cost of our water bills, helping us “Obtain a yield” while “Producing no waste”. Water cost is not too expensive but still, we would prefer to save as much as possible due to our limited income.

We wish to also lower the need to water our gardens frequently. Though precipitation is frequent, as it can be seen in the Site Survey there have been small periods of drought in the past few years. Also, the heat and the sun are extreme and can easily dry up the soil.

The quality of our tap water is a big concern because our water company chlorinates all the water it processes. We prefer not to use tap water directly on our gardens or for compost tea brewing.


We have no control over the gray water released from the main house because most guests bring their own products, thus no safe gray water could be collected from it. Another reason for not collecting gray water from the main building is that only 2” of this drain pipe is accessible and it is located slightly above soil level. This would require us to dig below it and bury a reservoir with a pump to move the water to a reservoir on the roof.


  • Lifelong building skills in iron and galvalume structures and average experience in concrete and wood working.

  • The distance between the two sections of the Zone 1 Garden and the tiny house is minimal.

  • The location to the west of the tiny-house, where the drain pipe is located, is roofed.

  • There are electrical outlets available around the back of the house.

  • The washer machine is already located in this area of the site.


Permaculture Ethics- Guidelines within which this design should be completed

  • Earth Care- Lower the amount of water wasted by using it, from source to sink. Dechlorinate water before using it for irrigation or compost tea brewing to avoid harming soil life. Exclusively use eco-friendly products to avoid water and soil contamination. Make of this a low energy system by taking advantage of gravity and integrating it with our solar PV system once implemented. Use repurposed materials like my old air pump and water pump.

  • People Care- Generate savings in water bills and lower the amount of labor needed to water our gardens. Increase the amount and quality of our yields by watering with enriched un-chlorinated water.

  • Fair Share- Return enriched grey water to our soil to provide a healthier habitat for all soil life. This would consequently feed all the animals that interact with healthier plants. Share this system and its benefits with guests, and offer it as an example in workshops and PDCs. Provide an example of a design that has regenerative purposes which clients can recreate in their homes.

Key Functions

Out of the Client Interview process, we can discern some specific functions related to this design from which our goals were set:

  • Lower costs related to water and fertilizer

  • Lower maintenance labor related to watering our garden.

  • Soil improvement- Have a source of nutrient rich, unchlorinated water to use on the garden, nursery and food forest (Law of Return- Mollison)

Secondary functions (functions that are not directly associated with a particular need, but that can support the system, therefore, solutions to the client’s needs and wants are successfully achieved) are:

  • Double as a system that aerates gray water for brewing compost tea. (Functional Relationship between components- Mollison)

  • Serve as an example of an eco-regenerative system that can be recreated by our guests and serve as an example of the “Produce no Waste” principle.

  • Serve as one of the example elements on PDC’s and workshops.

Options and Decision

There are a few options for gray water harvest systems that may work for this small project. Based on my experience with different trials and my research, the following list, shows what I have tried and what seems convenient:

Bucket under the sink (1) – This simple system has been tested for about a year or so. It involved just placing a bucket at the drain pipe and emptying it when full. Problems with it included:

  • Water turning stale because I would frequently forget about it.

  • Animals falling and dying in the bucket

  • My neighbor’s dog getting sick after drinking from the bucket

  • Having to constantly come out to empty the bucket

  • Having gray water constantly fall on the ground next to the house attracting insects.

Direct irrigation after use (2) - This system would involve a simple pipe extended from the drain pipe to the garden. A separate pipe would drain the washer machine on a separate section of the garden.

  • This system’s convenience comes from its simplicity and automation. If there was a need to stop the system due to overwatering, one could simply remove the pipe and use buckets for the water to be discarded.

  • The main problem with this system is that water goes straight to the soil without de-chlorinating, harming soil bacteria.

Automatic system with water pump (3), air-pump and reservoir.

  • Due to the low position of the drain pipe, the system cannot fill a large reservoir without using a water pump. Instead, water would fall in a 5 gallon bucket with a water pump inside to transport it to the reservoir. From this reservoir, I could install a spigot from which I can fill buckets to hand water the garden. Water would be dechlorinated using an air-pump.

  • This system does not eliminate the labour involved in watering our gardens.

  • This system would be inconvenient if all elements had to be purchased but I already had them from other projects and can be repurposed.

Automatic system (4) with water pump, air-pump, irrigation line, 2 hose-end timers and reservoir.

  • An alteration to system #3 but with the addition of a simple set of pipes that would transport the de-chlorinated gray water directly to 2 of the gardens on Zone 1.

  • An inconvenience of this system is that it involves the purchase of 2 hose-end timers so water remains on the reservoir long enough to be de-chlorinated. Each hose-end timer would control watering to each of our 2 adjacent gardens.

  • This system is convenient because it automatizes the whole process of collecting water and irrigation.

Function / System / Element

This system will need to perform the following functions:

  • Transport grey water to a reservoir

  • Aerate the water on the reservoir for its de-chlorination

  • A control system that releases water for specific intervals so it waters the gardens

3 simple systems can be integrated to fully perform this functions:

Gray water collector- Element and its function

    • Bucket- Collects graywater and can be used to irrigate by hand if the system fails.

    • Water Pump- Transports water to the reservoir once it reaches a certain level on the bucket.

    • Reservoir- Holds gray water from the house and washer machine in a single place.

    • Metal Base- Lifts the reservoir to a higher level to take advantage of gravity pressure.

Gray water aeration- Element and its function

    • Air Pump- Aerates water inside the reservoir. Extra air stones can be used to aerate compost tea separately.

    • Timer- Activates the air pump for 15 minutes intervals to avoid damage.

Irrigation system- Element and its function

    • Pipes- Transport aerated gray water to the garden

    • Hose-end timer- Controls irrigation to specific intervals to avoid overwatering and to allow time for gray water to be de-chlorinated by the air-pump.

I already own most of these items and they can be repurposed. This includes an air-pump which I used on my trials with hydroponics and a water-pump which we had as a safety measure in case of floods.

The Function / System / Element analysis, helps us seek for elements or systems that perform at least two functions or that have a symbiotic connection to other systems or elements. Out of this analysis, we can apply the “Recognize functional relationships between elements” principle, by adding a 4th system by using the extra air-stones I already have.

  • Compost tea brewing- would cover the needs stated on the Client Interview, of generating savings in fertilizer.

    • Element and its function

      1. Air Pump- Extra air-stones are already available (“Use Onsite Resources” principle) and can be plugged to unused air outlets. Separate buckets could be used to brew compost tea separately from the reservoir.

      2. Timer- Activates the air pump for 15 minutes intervals to avoid pump damage.

To this point, system 4 appears to be the most convenient. To confirm this, I used the following tool called SWOC (Strengths, Weaknesses, Opportunities and Constraints):

  • Strengths- Most elements are available on site (Water /Air Pumps, Timer and Hose end timer), elements that have proven to be very reliable. The system is fully automatic.

  • Weaknesses- It depends on electricity. In the case of a power failure, water can be collected in buckets and hand watered. “Redundancy” Principle

  • Opportunities- It could be integrated with my off-grid PV system because of its low energy consumption.

  • Constraints- If the air-pump fails it will not prevent chlorine from reaching the soil. Water buckets can be left under the sun to de-chlorinate naturally. “Redundancy” Principle

As a result of this process, I decided to use the fourth option.


For this design, the focus point will be the drain pipe which is a fixed point. This drain pipe combines the bathroom and kitchen sinks. There are not many options for the placement of this system due to this. The convenience of this area is that it is roofed which is necessary because it involves electric equipment.

This area is also located right next to our kitchen and bathroom’s window. Although, this is a system that requires little maintenance, it is convenient for it to be close enough so we can notice any failures. This area is also convenient because it also holds the washer machine which could easily drain into the reservoir.

Following the principle of “Relative Location” the main elements of this system should be located close to each other as to avoid strain of the pumps and to be easily understood as a single system for students and visitors.

Waste water amounts

(Average amounts based on Table 2.2:Example of Wastewater amounts, Page 11 of Creating an Oasis with greywater). There is no data on the specific monthly use because the utility company has been estimating the same consumption amount for the past 7 years.

  • Washer: 1 load per week x 32 gal/ load= 32 gpw

  • Kitchen Sink: 3 gal. a day per person x 1 person x 7 days= 21 gpw

  • Bathroom Sink: 2 gal. a day per person x 1 person x 7 days= 14 gpw

Applicable Permaculture principles

  • Catch and Store Energy- Take advantage of our water energy, from source to sink, by reusing it for our gardens and compost tea.

  • Obtain a Yield- Increase the yields of our garden through proper watering with enriched un-chlorinated water.

  • Apply Self-Regulation and Accept Feedback- Take into consideration my experience with my “bucket under the sink” design to make better decisions.

  • Produce no Waste / Law of Return (Mollison)- Decrease water waste from this residence by taking advantage of it at many levels until it reaches the soil.

  • Functional Relationship between components (Mollison)- Integrate a separate system for compost tea brewing. Take advantage of the location of the washer machine to use another source of gray water.

  • Relative Location / Make the least change for the greatest possible effect (Mollison)- Take advantage of the area where the fixed point is, the drain pipe, to place all elements near to each other in an area that is already roofed and where the washer is already located.


The following illustrations show the outcomes of the survey and analysis process and helps structure its implementation. No CAD program was used for this design.

The system above, shows the drain pipe from which, all gray water used on the tiny-house drains from. All water will fall into a 5 gallon bucket which will be holding an automatic water pump which activates once water reaches certain level inside the bucket. At that moment, the water in the bucket gets transported into the reservoir using an old hose (upgraded into repurposed pvc pipes). There is also a pipe that goes from the washer machine into the reservoir for additional collection.

Inside the reservoir are two air-stones, connected to an air-pump next to the reservoir. This air-pump is connected to a timer which turns it on, every 15 minutes. Two separate air-stones are available for compost-tea brewing. These air-stones not only de-chlorinate but also limit the proliferation of anaerobic bacteria in the reservoir.

A spigot is installed on the reservoir to facilitate access to gray water for compost tea brewing and hand watering.

From the bottom of the reservoir, an old repurposed PVC pipe will be connected which will transport water to the hose-end timers. These timers activate twice a day, opening for a set time, depending on precipitation. Water gets transported from the timer through PVC pipes to each of two adjacent gardens. Grey water is released directly to the soil under the mulch. No root crops should by planted on these gardens. (See: Zone 1 Garden design for specific plants chosen)

Irrigation- To avoid clogging, the system is kept simple by only using PVC tee fittings all along the irrigation pipe. This pipe is attached to the fence with brackets only and no part is glued to allow for adjustment and even distribution of water.

The diagram also shows the placement for each of the elements behind the tiny-house next to the concrete fence (South-westernmost side of the site). This area has the main fixed point, the drain pipe, from which the system feeds. This area is also where the washer machine is already located and two of the three Zone 1 gardens are near this area.


2014: Late- My first attempts at grey water harvesting involved using a simple 5 gallon bucket as a collector. This system immediately showed problems when I noticed the dogs drinking the water and animals falling in the bucket and dying. Other problem came up from water becoming stale when I was away from the home for a few days or forgot about it.

  • 2016: March 12- Partial implementation of the “Zone 1 Garden” planting areas. (Integrated design)

  • 2016: April- Read the book: Create an Oasis with Greywater. Used as a general guide for this design.

  • 2016: May 16- Performed testing in Compost tea brewing using cheesecloth bags on 5 gallon buckets.

  • 2016: May 17- Purchased a 50 gallon reservoir for $35.

  • 2016: May 19- Built a raised metal structure for the 50-gallon reservoir. Installed a spigot at the bottom of the reservoir’s side.

  • 2016: May 23- Installed a customized PVC adapter with a pressure gasket to the bottom of the reservoir, for a connection to the irrigation system. Also, cut open an access door to the top for cleaning and for the air stones. Drilled a hole for an additional PVC pipe at a lower level than the access door to prevent overflowing. Connected two pipes to the top for access from the water pump and the other for the washer machine.

  • 2016: May 25- Adapted a 5-gallon bucket to collect gray water directly from the drain pipe. Inside I placed an automatic water pump which I connected to the reservoir using an old hose which I then replaced with old PVC pipes running under the soil.

  • 2016: May 27- Started building a very simple irrigation system with additional access points using old pvc pipes.

  • 2016: June 1 - Started making compost tea directly in the reservoir but I noticed that sediment could clog the system. First trial with an old hose-end timer showed it did not work unless it had enough water pressure. Ordered two low pressure hose end timers.

  • 2016: June 10- Finished the irrigation pipeline to the first section of the “Zone 1 Garden” using one low-pressure hose-end timer.

  • 2016: June 12- Integrated a very simple compost tea brewing system by placing 5 gallon buckets near, and using two extra air-stones connected to the same air-pump that feeds the inside of the reservoir.

  • 2016: June 20- Started working the second section of the “Zone 1 Garden’s” irrigation pipes.

  • 2016: July 15- Completed and activated the Grey Water Harvester after finishing all trials.

Cost Summary

5 Gallon Bucket- Donation

50 Gallon Reservoir- $35

Air Pump with air stones- repurposed from hydroponic trials

Water Pump- Repurposed (Previously purchased years ago for other purposes)

PVC System and hoses- Repurposed

2 Hose-end Timers- $80

Raised metal structure for reservoir- Repurposed galvalume.

Framework used: Gobradime

Maintenance and Monitoring

  • A light clean-up of the bucket, water pump, air stones and the inside of the reservoir should be made every 7 -15 days. This can be done with just a hose with regular tap pressure.

  • Every 3 months, a light soap and a brush can be used to eliminate any persistent sediment.

  • In the case of failure, if unable to repair, the broken element should be replace by an equivalent machine of the same size.

  • Leaks should be repaired by tightening or adjusting fittings


What went well:

Having most of the elements already on site was advantageous. The main elements, air-pump and the water pump have been used frequently for years showing they are extremely reliable. Once this system was activated, it did not require any maintenance for months, fulfilling the “need” of lowering maintenance labor. Also, almost all of the gray water generated on the tiny house was used in the garden and for compost tea, achieving the goal of saving in water cost and enriching the soil with de-chlorinated water (Produce no waste / Obtain a yield).

What I would have done differently:

I started collecting grey water way before having this design in mind which led me to several failures. The main error was, holding the water in an open bucket and forgetting about it. This caused dogs to get sick from drinking the water, lizards falling in it and drowning and water going stale. This serves as an example of the value of designing before implementing.

The use of old hoses caused some strain in the pumps when they bended. Most of it was replaced with repurposed PVC pipes.

Learning Pathway Reflections:

This system has showed me that with little effort, I can significantly reduce my use of such a valuable resource as water helping us to “Produce no waste”, while also returning it into the soil in a better state, to feed my plants and soil life. It has also shined a spotlight into what I consume and what the repercussions are for the environment if I don’t consume consciously and don’t take the whole cycle into consideration.

How this design helps me apply permaculture in my life:

This design has certainly shown me that I can multiply the benefits of my efforts through the integration of different designs like it was done when I combined the compost tea brewing system with this one, “Integrate rather than segregate”. It also has taught me that, with minimal effort, (simple bucket under the sink) or a moderate effort (automatic system) I can significantly reduce my impact on the planet.

How this design helps me apply permaculture in my works and projects:

Consultancy and Development- My experience after implementing and using this design, gives me the confidence to offer it to potential clients that are interested in having any of the benefits of a Gray Water Harvester. The system itself can serve as a live example to potential clients who wish to visit my site.

Education- This design and all its parts are easily accessible so they can become part of a PDC class. This would be a living example so the learning experience is richer compared to showing just pictures and diagrams.

Principle 7: Design from patterns to details

By stepping back, we can observe patterns in nature and society. These can form the backbone of our designs, with the details filled in as we go.

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