We want to design a greywater system for bathrooms we're renovating. Can you help?

Asked by Brian McDonald, Providence, RI

We're rehabbing a campground and looking for greener ways to do things. I saw a Planet Green show where they rehabbed a bathroom and used greywater to flush the toilet. Is there a way we can do this? The amount of water waste is incredible—I would love to reclaim some or all of it.


Jesse Terzi

Answered by Jesse Terzi

Inwood, NY

New Eco, Inc.

April 23, 2009

Your toilets are a great way to recycle grey water.  In most cases the water collected for greywater comes from showering or bathing, but greywater can also be collected from vanity sinks, washing machines, AC condensate drains, and rainwater. The water then goes to a secondary use such as toilets or irrigation systems.

One of the easiest ways to incorporate greywater use into your home is to:

  • collect the water directly from the bathroom sink,
  • store and treat it in a small tank kept in the vanity, and
  • pipe it directly to the toilet's flush tank.

Greywater systems

You can build a simple greywater system yourself (and there are links below to sites that explain how), but I do not recommend it unless you have a broad knowledge of plumbing and greywater. An improperly designed greywater system can lead to a myriad of problems.

I recommend purchasing a system and having it professionally installed.

  • One of the small systems our company uses is the Aqus from WaterSaver Technologies. This system works great, is moderately priced at around $300, and will not cost much to install if you have a good plumber.
  • For large projects, we use Brac Systems, which is a high-tech system that easily collects water from multiple sources and treats, stores, and distributes it to toilets or other greywater applications. This system also has a freshwater backup that kicks in if not enough greywater is being generated, so you're not left with dry toilets.
  • It is important to properly size out your system because greywater stored for more than 24 hours is considered "black water"—it produces a foul smell and cannot be used. If you size your system too big, you will collect much more greywater than you will be using, forcing the system to discharge most of it to the sewer. And if you are using much more water than you are collecting, the system will have to supplement the demand with fresh water.

Retrofit vs new construction

It is a little more costly to retrofit greywater plumbing, as opposed to doing it in new construction, but is still not that big of a deal.

For new construction, if you're interested in transitioning to greywater in the future but not ready to build a system yet, have your plumber run piping that can easily be converted for greywater. It will make it much less expensive when you decide to switch to greywater later.

Using every drop of water you can

With a campground, I imagine you want to collect and use every drop of water you can.

  • If you want to start using greywater collected from more than one fixture or source, I recommend a professionally designed system that is connected to the plumbing. 
  • Greywater coding can be tricky. It varies from state to state and is mainly contingent on your local officials and inspectors. 
  • We highly recommend having a greywater system designed, built, and installed by a professional who can help you handle the coding issues prior to installation.

For your campground, you should also consider using greywater and rainwater for irrigation and maybe designing outdoor systems such as bioretention basins and constructed wetlands to maximize water conservation. Using these systems will let you collect all the water that touches the property. Keep in mind, however, that you should never discharge greywater directly into natural waterways. And when using greywater to water fruits or vegetables, it is best not to water the edible parts of the plant.

Be careful with what goes down the drain

Once the greywater system is in use, you will need to be careful what you pour down the drain.


For more information:

Read Randy Potter's Q&A "Is it feasible to reuse greywater as irrigation water?"

Oasis Design has a great website that should answer almost any question you have about greywater. They have loads of information, including a state-by-state policy guide. They also sell some really great books for building greywater systems.

Another of my favorite sites about greywater is The Greywater Guerrillas. This site has a lot of DIY building information if you want to get your hands dirty.

Tagged In: water saving, greywater

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