InspectAPedia®   -   Search InspectApedia

Water saving toilet: toilet tank-sink combination (C) Daniel Friedman Greywater or Graywater Toilet Flush Systems
Water Conservation, Re-Use, Graywater Toilet Flushing

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.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Use of Graywater to Flush Toilets

Water saving toilet: toilet tank-sink combination (C) Daniel Friedman

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

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. We do not sell products nor services.

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

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

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

Suggested citation for this web page

GREYWATER FLUSH TOILETS found at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to SEPTIC SYSTEMS

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification
when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.
Our Comment Box is provided by Countable Web Productions countable.ca

Comment Form is loading comments...

Citations & References

In addition to any citations in the article above, a full list is available on request.



ADVERTISEMENT