Flush toilets using graywater:

This article describes the use of greywater to flush toilets, reviewing the benefits of water conservation and the risks of soil or nearby water supply contamination, odor complaints, bacterial hazards.

We include citations of authoritative research on gray-water re-use for flush toilets and on graywater disposal into septic systems.

This article series defines and explains the disposition of greywater, a type of wastewater, as a water conservation measure and for re-use in watering plants, crops, or for other applications.

Use of Graywater to Flush Toilets

Our photo shows a toilet flush-tank or cistern top that incorporates a wash basin. This water-saving feature feeds fresh water, though not necessarily potable water, to the wash basin and drains the used water (from washing hands) into the toilet cistern to be used for the next toilet flush.

This toilet is installed at the Nirvana restaurant in Guanajuato, Mexico, near San Miguel de Allende.

Question: We want to use our soapy shower water to flush our toilets

Giesela said:

We want to use our soapy shower water to flush our toilets with, as we are in a drought stricken area. No other water goes into the septic tank.Will the soap have a bad influence on the conditions in the septic tank?

- 2017/08/01, this question and our reply were posted originally at SEPTIC TREATMENT FAQs

Reply:

Gisela,

Is it OK to use graywater exclusively to flush toilets & to send into the septic tank and drainfield?

For other readers, “Graywater” is defined (for example) by the California Graywater Standards in the California (US) Administrative Code, as “untreated household wastewater that has not come into contact with toilet waste. More practically, graywater is wastewater from bathubs, bathroom lav basins (sinks), showers, and clothes washers.

Watch out: wastewater from kitchen sinks and dishwashers as well as washing machine wastewater from laundering dirty diapers is heavily contaminated with various pathogens and should be sent to the septic system, nolt into the separate graywater system that would handle the graywater sources I listed just above.

For short term situations you can certainly dump by hand soapy water into a toilet tank to flush the toilet. Sending that limited volume of soapy sink water into a toilet tank and thence into a septic system should not make one iota of difference to a conventional septic tank/drainfield in systems where all of the building’s plumbing fixtures already drain into the septic tank and absorption field.

Watch out: longer-term use of un-treated graywater for flushing toilets can lead to odor complaints as well as to bacterial hazards in the toilet itself. (Jeppsen 1996) (Albrechtsen 2002). Use of graywater for toilet flushing might safe as much as 35% of drinking water, but additional treatment of the water for disposal will be needed. (Mourad 2011)

Generally using graywater (sink and tub or shower waste) to flush toilets is a water-conservation method that is used in areas where water conservation is important.

There are in fact toilets that incorporate a hand sink above the toilet tank specifically to aid that purpose. The example of a toilet top lavatory sink (shown above) is discussed

at TOILETS, WATERLESS ALTERNATIVES

Also see FILTERS SEPTIC & GREYWATER for graywater filters used to protect septic systems from debris in graywater, the first step in making graywater useful for watering grass, trees, plants, etc.

But there is more we should consider about proper handling of graywater when we start collecting all building graywater for disposal. Where should that wastewater go and how should it be best handled to protect the septic system and the evnironment?

Over a longer term there are concerns with sending all graywater-wastewater that's high in lint (from washing machines) or soap, and un-filtered, un-treated, into a septic system. Both of these ingredients can clog the drainfield (lint and soap film) and also because the chemistry of detergents high in phosphates (for example) may be harmful to local soils or to nearby wells or water sources. For those systems a graywater treatment system is what’s appropriate.

Home & Small Building Greywater Treatment Systems

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• CONDENSATE DISPOSAL REQUIREMENTS, California Building Code (2013) [PDF] retrieved 2017/07/17, original source: https://docs.vcrma.org/images/pdf/bs/ 2007_Adopted16A_Revised-1-20-2010.pdf as adopted by Ventura County in 2010
• NEW MEXICO GRAYWATER BILL [PDF] House Bill 711, (2005) retrieved 2017/08/02, original source: https://www.nmlegis.gov/Sessions/05%20Regular/bills/house/HB0711.pdf
• NSF/ANSI Standard 350 and 350-1: Onsite Water Reuse, available from http://www.nsf.org/ Tel: +1 734.827.6846 or email wastewater@nsf.org.
  Excerpt:
  
  NSF/ANSI 350 and 350-1 establish material, design, construction and performance requirements for onsite residential and commercial water reuse treatment systems. They also set water quality requirements for the reduction of chemical and microbiological contaminants for non-potable water use.
  
  Treated wastewater (i.e. treated effluent) can be used for restricted indoor water use, such as toilet and urinal flushing, and outdoor unrestricted water use, such as lawn irrigation.
• NSF/ANSI Standard Aesthetic Effects & NSF/ANSI Standard 53, Health Effects of Drinking Water Treatment Units, [PDF] retrieved 2017/08/02, original source: https://www.nsf.org/newsroom_pdf/water_42_53_insert.pdf
  NSF International, 789 N. Dixboro Road, Ann Arbor MI 48105 USA, email: americas@nsf.org or asia@nsf.org
  
  Excerpts:
  NSF/ANSI 42 is one of two main NSF standards that set the benchmark for evaluating safety and integrity of residential water filters.
  
  NSF/ANSI 42 establishes the minimum requirements for the certification of POU/POE filtration systems designed to reduce specific aesthetic or non-health-related contaminants (chlorine, taste, odor and particulates) that may be present in public or private drinking water.
  
  The scope of this standard includes material safety, structural integrity and aesthetic, structural integrity and aesthetic claims. The most common reduction claims addressed by this standard are chlorine, chloramines, iron, manganese, hydrogen sulfide, pH neutralization and zinc reduction.
  
  In addition, products certified only as components are found under NSF/ANSI 42 and are evaluated for material safety and, if pressure bearing, structural integrity.
  
  NSF/ANSI 53 is the second NSF benchmark standard that addresses reduction claims for residential water filters.
  
  This standard establishes the minimum requirements for the certification of POU/POE filtration systems designed to reduce specific health-related contaminants, such as Cryptosporidium, lead, volatile organic chemicals (VOCs) and asbestos that may be present in public or private drinking water.
  
  The scope of this standard also includes material safety, structural integrity and other health-related contaminant reduction performance claims. The most common reduction claims verified by this standard are heavy metals, inorganics and volatile organic chemicals.
• Australia: Aquacell Water Recycling, 64 Alexander St Crows Nest NSW 2065 Australia Phone: +61 2 4721 0545 Website: http://aquacell.com.au/
  Website excerpt:
  The Aquacell G Series provides a simple modular solution for on-site greywater recycling. The system features a controlled, robust and comprehensive treatment process that combines physical, microbiological and oxidative treatments in one efficient package.
• Australia: Nubian Water Systems 25-27 Whiting Street Artarmon NSW 2064 Australia Tel: 1-800-682426 or 02 9438 5522 Website: http://www.nubian.com.au/ provide greywater recycling equipment, rainwater re-use, wastewater recycling, and drinking water purification systems.
  
  The company provides an OASIS Domestic Greywater Treatment System (GT600) reported to save close to 400 litres of drinking water each day for a typcial family of four. ($AUD about 7,500) Website promotional page excerpt:
  
  The Oasis Greywater System uses a chemical free process in treating household greywater. Designed and built as a compact, modern appliance, the Oasis Greywater System is a high performance system which can produce treated water suitable for irrigation, washing paths, cars and garden, toilet flushing and even for clothes washing!
  
  This innovative system will accept water from the laundry, shower, bath and hand basins and is fully automatic with little involvement by the user. To provide a high level of confidence that the system's performance is always at its best, the Oasis Greywater System can be remotely monitored by Nubian Water Systems.
  
  Nubian Water Systems' proprietary, high intensity biological process, coupled with UV disinfection, allowed for the development of a compact greywater appliance which is different to most greywater systems in the market.
• RainHarvest Systems, LLC 4475 Alicia Lane Cumming, GA 30028 USA Tel: 770-889-2533, Tel: 800-654-9283, Aqua2Use, greywater recycling system, recycles laundry, shower, bath water, processes it through a filter, then diverts the water to an irrigation system. Small size, compact, (About $2000. USD). Website: http://www.rainharvest.com/aqua2use-greywater-recycling-system.asp
  
  AQUA2USE INSTALLATION & OPERATION MANUAL [PDF] retrieved 2017/08/01,original source: http://www.rainharvest.com/info/aqua2use/Aqua2use-GWDD-Instruction-Manual.pdf
• U.S. The ReFlow, 1234 Santa Monica Blvd Beverly Hills, CA 90210 USA, produces the ReFlow graywater recycling system similar to the Nubian system above but apparently more-compact such that it can fit inside of a residential bathroom.
  
  This is a lower-volume unit producing enough recycled lav or tub or shower water for about 5 toilet flushes per day. Status: "Developing Prototype in Vancouver, BC, Canada. Securing patents ."

Research on Use of Graywater for Flushing Toilets

and Research on impact of soap and graywater on septic systems & on detergents in & escaping the septic system

• Albrechtsen, H-J. "Microbiological investigations of rainwater and graywater collected for toilet flushing." Water Science and Technology 46, no. 6-7 (2002): 311-316.
  Abstract:
  
  Seven Danish rainwater systems were investigated with respect to the microbial water quality. The general microbiological quality (total numbers of bacteria (AODC)), and heterotrophic plate counts on R2A and Plate Count Agar in the toilets supplied with rainwater were approximately the same as in the reference toilets supplied with drinking water.
  
  However, in 12 of the 27 analysed samples one or more pathogens were observed (Aeromonas sp., Pseudomonas aeruginosa, Legionella non-pneumophila, Campylobacter jejuni, Mycobacterium avium, and Cryptosporidium sp.).
  
  These pathogens were not found in any of the reference toilets (32 toilets).
  
  This means that the use of rainwater introduced new, potentially pathogenic micro-organisms into the households which would normally not occur in toilets supplied with water from waterworks. Furthermore, four graywater systems were investigated where water from the shower and hand wash basin was reused.
  
  The graywater systems gave more problems in terms of bad smell and substantially higher numbers of E. coli and Enterococcus in some toilet bowls supplied with graywater.
• Alhajjar, Bashar J., John M. Harkin, and Gordon Chesters. "Detergent formula and characteristics of wastewater in septic tanks." Journal (Water Pollution Control Federation) (1989): 605-613.
  
  Abstract:
  Septic system treatment of wastewater containing phosphate (PO₄)-built or carbonate (CO₃)-built detergents was evaluated.
  
  For 2 years monthly effluent sampes were taken from 17 household septic systems adn were analyzed fo rphysical, chemical, and biological parameters.
  
  Wastewater loads to each septic system were measured and detergent use and laundering activity records were kept. Results showed surfactants were degraded in the septic tanks.
  
  Alkalinity, temperature, sodium, potassium, calcium, magnesium, chloride, sodium adsoprtion ratio, electrical conductivity, solids, biological oxygen demand [BOD], and counts of indicator bacteria were higher in wastewater with PO₄-built detergent use.
  
  The use of PO₄-built detergent significantly increased the total phosphorous load in effluents. However, better removal of total nitrogen was achieved with the use of PO₄-built detergent.
  
  The CO₃-built detergent increased the buffer capacity of wastewater; no significant differences in pH were found in the two types of wastewaters resulting from detergent use. J. Water Pollut. Control Fed., 61, 605 (1989)
• Christova-Boal, Diana, Robert E. Eden, and Scott McFarlane. "An investigation into greywater reuse for urban residential properties." Desalination 106, no. 1-3 (1996): 391-397.
  Abstract:
  
  Continuing moves towards full cost recovery for potable water and the impending privatization of water supplies in the Melbourne area have enhanced public interest in the reuse of wastewater, and particularly the domestic use of greywater. V
  
  ictoria University of Technology, together with support from Melbourne Water and the Department of Health and Community Services, has been investigating the practicalities, costs and social attitudes of using greywater in and around the home.
  
  Four “typical” Melbourne homes were selected and plumbed to utilize greywater for toilet flushing and garden irrigation. Social surveys were conducted by mail and phone to homeowners to determine perceived attitudes towards greywater reuse.
  
  Greywater from baths, showers, laundry troughs and washing machines is being examined for physical, chemical and microbiological parameters to determine the potential health and environmental risks associated with reuse.
  
  Soil tests were also undertaken on gardens to determine any long-term detrimental effects that might occur as a result of using greywater. This paper describes the greywater testing, results of filtration and filter designs, appropriate disinfectants, and physical findings to date. The two-year project is due for completion early in 1995.
• Deluty, Jerome. "Synthetic detergents in well water." Public Health Reports75, no. 1 (1960): 75.
  Abstract excerpts:
  
  Septic system treatement of wastewaters containing phosphate (PO4)-built or carbonate (CO3)-built detergetns was evaluated. For 2 yars monthly effluent samples were taken from 17 household septic systems and were analyzed for physical, chemical, and biological parameters. …
  
  The use of PO4-built detergents significantly increased the total phosphorous load in effluent. However, better removal of total nitrogen was achieved with the use of PO4-built detergents.
  
  The CO3-built detergent increased the buffer capacity of wastewater; no significant differences in pH were found in the two types of wastewaters resulting from detergent use. J. Water Pollut. Control Fed., 61, 605 (1989)
• Dixon, A., D. Butler, and A. Fewkes. "Water saving potential of domestic water reuse systems using greywater and rainwater in combination." Water science and technology 39, no. 5 (1999): 25-32.
  Abstract:
  
  For a sustainable urban future, society must move towards the goal of efficient and appropriate water use. Reuse of domestic greywater and rainwater has a significant role to play in this task. In this study, rainfall time series have been used in conjunction with estimates of domestic water appliance usage generated by the Monte-Carlo simulation technique to predict long term system performance.
  
  Model results show that changes in the attributes of household occupancy, roof area, appliance type and storage volume affect the water saving efftciency of a single store reuse system. Considering greywater and rainwater in combination, the greatest rate of increase of efficiency with storage size occurs in the range 0–100 litres.
  
  Further analysis of small volume storage and reuse indicates that savings of up to 80% of the WC flush water can be made with less than 50 litres storage.
  
  However, the collection of rainwater in addition to greywater in a single store reuse system offers little improvement in water saving efficiency.
  
  Small volume domestic water reuse systems lend themselves to application in the urban housing environment and therefore offer potential in the move towards a more sustainable city.
• Jeppesen, B. "Domestic greywater re-use: Australia's challenge for the future." Desalination 106, no. 1-3 (1996): 311-315.
  
  Abstract:
  Under a grant from the Urban Water Research Association of Australia, the Brisbane City Council has advanced Australian research into domestic greywater re-use. This hard work has established that domestic greywater does contain chemicals and microorganisms that can be harmful to public health and the environment.
  
  Greywater can even emit noxious odours. However, if domestic greywater could be re-used to water lawns and ornamental gardens, the average household potable water usage could be reduced by between 30–50%. Public acceptance of the principle is high, but this must be balanced against the incorrect perception that greywater is innocuous. The challenge now facing Australian Water Authorities is how to fully utilize this valuable resource without: compromising public health, causing detrimental impact to the environment or down grading the livability of our residential areas.
  
  Only through total management and public awareness of the issues is this possible. To help achieve these goals the Brisbane City Council is presently developing guidelines for the application of domestic greywater re-use for sewered areas in Australia. This paper provides a brief overview of this research and an insight into the direction of these proposed guidelines.
• Lazarova, V., S. Hills, and R. Birks. "Using recycled water for non-potable, urban uses: a review with particular reference to toilet flushing." Water Science and Technology: Water Supply 3, no. 4 (2003): 69-77.
  
  Abstract:
  This paper summarises the current non-potable, urban use of reclaimed water with particular reference to toilet flushing. It compares water quality standards for reclaimed water, the volumes of water required for toilet flushing and the qualities of greywater and domestic sewage that have previously been used for reuse.
  
  Worldwide examples of reuse schemes are presented with particular detail to two key European sites where greywater has been used for toilet flushing, the Millennium Dome in the UK and a residential block of flats in Annecy, France. It was demonstrated that the interest in water reuse is growing steadily, not only in acknowledged water deficient areas, but also in countries which have not historically appeared to have a water supply problem.
  
  The latter include Northern European States such as Belgium, France, the UK and Germany, as well as in tourist coastal areas and islands. This situation affords great opportunities for the creation of urban water recycling schemes.
• March, J. G., M. Gual, and F. Orozco. "Experiences on greywater re-use for toilet flushing in a hotel (Mallorca Island, Spain)." Desalination 164, no. 3 (2004): 241-247.
  
  Abstract
  An indoor greywater recycling system to flush the toilets in a hotel is described. The system is based on filtration, sedimentation and disinfection treatments using hypochlorite as the disinfecting agent. An average amount of water of 5.2 m3/d−1 was re-used, which represents 23% of the total water consumption of the hotel.
  
  A moderate hypochlorite dose (75 mg chlorine l−1) and a controlled residence time (<48 h) led to a residual chlorine concentration at cistern toilets higher than 1 mg l−1. Under such conditions, all samples were negative for total coliform bacteria. A maintenance program was proposed and an economics assessment was also reported.
  
  Customer acceptance was clearly satisfactory. This is the first paper reporting data on greywater reuse for toilet flushing in a hotel.
• Mourad, Khaldoon A., Justyna C. Berndtsson, and Ronny Berndtsson. "Potential fresh water saving using greywater in toilet flushing in Syria." Journal of environmental management 92, no. 10 (2011): 2447-2453.
  
  Abstract:
  Greywater reuse is becoming an increasingly important factor for potable water saving in many countries. Syria is one of the most water scarce countries in the Middle East. However, greywater reuse is still not common in the country. Regulations and standards for greywater reuse are not available. Recently, however, several stakeholders have started to plan for greywater reuse.
  
  The main objective of this paper is to evaluate the potential for potable water saving by using greywater for toilet flushing in a typical Syrian city. The Sweida city in the southern part of Syria was chosen for this purpose. Interviews were made in order to reflect the social acceptance, water consumption, and the percentage of different indoor water uses.
  
  An artificial wetland (AW) and a commercial bio filter (CBF) were proposed to treat the greywater, and an economic analysis was performed for the treatment system. Results show that using treated greywater for toilet flushing would save about 35% of the drinking water.
  
  The economic analyses of the two proposed systems showed that, in the current water tariff, the payback period for AW and CBF in block systems is 7 and 52 years, respectively. However, this period will reduce to 3 and 21 years, respectively, if full water costs are paid by beneficiaries. Hence, introducing artificial wetlands in order to make greywater use efficient appears to be a viable alternative to save potable water.
• Nolde, Erwin. "Greywater reuse systems for toilet flushing in multi-storey buildings–over ten years experience in Berlin." Urban water 1, no. 4 (2000): 275-284.
  
  Abstract
  Water reuse in Germany has gained in significance in the last 10 years. Several greywater systems, built according to guidelines introduced in 1995, operate today with no public health risk.
  
  Two greywater treatment systems are described in this paper: a rotary biological contactor (RBC) built in 1989 for 70 persons, and a fluidized-bed reactor for a one-family household built in 1995 as the biological stage for the treatment of household greywater for use in toilet flushing. Both systems were optimized in the following years with consideration of a minimal energy and maintenance demand.
  
  As numerous investigations have shown, biological treatment of the greywater is indispensable in order to guarantee a risk-free service water for reuse applications other than potable water.
• Surendran, S., and A. D. Wheatley. "Grey‐water reclamation for non‐potable re‐use." Water and Environment Journal 12, no. 6 (1998): 406-413.
  
  Abstract:
  Direct water recycling has become an important part of water conservation in the dry areas of the world and is now being seriously considered for the UK.
  
  This paper reviews current demands in large buildings and balances these against non-potable re-use. Work is also described on the development of a sustainable low running cost treatment unit.
  
  Results are presented from a 751/day prototype biological process operated with a synthetic sewage, which achieved a near potable standard at a cost of 25 p/m3. The design, performance and costings of a 40 ‘population equivalent’demonstration unit are also given.

Keywords: Domestic greywater,domestic graywater,greywater re-use,graywater re-use,graywater for flushing toilets,water re-use,australia,U.K.,Syria,Mallorca,Spain,toilet flushing,hypochlorite,greywater,

Also see

• HOOT Aerobic Systems Drip Disposal Design & Installation Guide [PDF]
• "Guidance For Design, Installation And Operation OF SUBSURFACE DRIP DISTRIBUTION SYSTEMS As A Replacement For Conventional Title 5 Soil Absorption Systems For Disposal Of Septic Tank Effluent", [PDF] Massachusetts Department of Environmental Protection (2006) refrencing MA regulations 310 CMR 15.240, 15.242, 15.247, and 15.280-15.289

Question: Does Washington State prohibit graywater systems?

I am having issues with my septic system and the service that has started my job is telling me that in Washington State it is a state law that we cannot use Grey Water systems. Do you happen to know anything about that? I am very interested in adding a system like yours for my home. Please let me know. Thank you - D.W. 5/15/2014

Reply:

Washington State does not prohibit graywater re-use but does specify guidelines and the state allows local jurisdictions to enforce more strict regulation. Indeed the state has published various studies and guidelines.
Quoting from your state's own publications

Chapter 246-274 WAC sets requirements for using greywater for subsurface irrigation. The rule took effect on July 31, 2011. Local health jurisdictions (LHJs) have three years to implement it. (LHJs may adopt more stringent requirements than those in the state rule.)

However, if they are unable to adjust resources to implement and enforce this chapter, the provisions of chapter 246-272A WAC shall continue to apply to greywater reuse for subsurface irrigation. Check with your LHJ to learn if greywater reuse under chapter 246-274 WAC is allowed or ask them how to support that effort if it is not allowed yet.

Watch out: Washington State authorities (and the WA law), in discussing the re-use of graywater and the design of graywater systems does make clear that installing a graywater re-use sysem does not exclude septic systems (onsite wastewater disposal systems or soakawy beds or soakpits depending on where you live) from meeting other state requirements for those systems.

In other words, if your septic system needs a new drainfield, it will still need one after installing a graywater re-use system. However on occasion one can extend the life of a septic drainfield by reducing the water load on it by routing graywater elsewhere.

...

Continue reading  at GREYWATER SYSTEMS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• ALTERNATIVE & WATERLESS TOILETS
• CISTERN & RAINWATER COLLECTION SYSTEMSa combination of rainwater collection and graywater collection, diversion, re-use on a home built in an area of water scarcity
• GREYWATER SYSTEMS - home
• DEFINITION of GRAYWATER SYSTEMS
• FILTERS SEPTIC & GREYWATER
• TYPES of GRAYWATER SYTEMS PRODUCTS
• USE GRAYWATER to REDUCE SEPTIC LOAD
• GREYWATER DISINFECTION BEFORE RE-USE
• GREYWATER FREEZE PROTECTION
• GREYWATER CODES & REGULATIONS
• GREYWATER FLUSH TOILETS
• GREYWATER RE-USE & RAINWATER COLLECTION SYSTEMS
• GREYWATER SYSTEM PRODUCTS, SUPPLIERS
• WASHING MACHINES & SEPTIC SYSTEMS
• WATER CONSERVATION MEASURE

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