Gray Water 101 – Your Guide To Reusing Household Water

Gray Water 101 - Your Guide To Reusing Household Water

You’ve probably heard about gray water and how you can use it around the home.

It has many benefits, such as making you more sustainable because you can decrease how much water you waste.

It’s shocking to consider that every day the average person in the U.S. uses 88 gallons of water, as the Environmental Protection Agency reports, which is the equivalent of approximately 333 liters!

What, exactly, is gray water?

Gray water is water that’s been used in showers, tubs, washing machines, and bathroom sinks but hasn’t come into contact with human waste. It can, however, contain traces of food, household cleaning products, and other substances.

The above description might make you wrinkle your nose at the thought of using gray water for other purposes.

But it shouldn’t because gray water can do many great things – mainly, instead of being wasted, this gently used water can be put to more good use.

With that in mind, let’s explore gray water in greater detail.

How To Use Gray Water

Using Gray Water In Garden

If you want to start making use of the gray water your home produces, you might be wondering where to start.

One of the best ways to use your gray water is in the yard.

While the pollutants in gray water could be harmful to large bodies of water, such as lakes or rivers, these are perfectly safe for use in your garden.

And, by using them in this way, you prevent them from entering those large bodies of water, so it’s a much more eco-friendly choice

To use gray water, you first have to collect it. If you’re using gray water in your garden, you can easily do so by running a pipe that collects water directly outside.

This will be an easy way for you to use gray water to hydrate your ornamental plants.

Other Ways To Use Gray Water

Of course, you don’t just have to use gray water in your yard. You can use it for other purposes, such as the following:

  • Use it to flush your toilet. This is a really easy way to get started with using gray water. You can collect water from basins and bathtubs with buckets and then use it to flush your toilet.
  • Use it to water your houseplants. If you collect water in the same way as mentioned above, with the use of buckets, you can quickly and easily water your houseplants with it so that the water doesn’t get thrown away. 

Pro tip: Another way in which you can collect water from the bathroom basin instead of collecting it with buckets is to remove the J-trap from underneath the basin and then replacing it with a bucket. Just make sure you always keep an eye on it so that water doesn’t overflow!

  • Pump out your bathtub or shower water. A bit of plumbing is all you need to ensure you can pump water from these areas in the home into the sewer line or into a gray water system. You’ll need a three-way valve for this purpose.
  • Use water from the washing machine. You can make use of water that’s been used to wash your clothes by removing the machine’s discharge house from the house drain. Then, you can connect it to a hose that will be able to reach, and water, your garden. This is a fantastic way to make use of gray water, but you have to ensure that you don’t use chemicals in your laundry detergents otherwise these will pollute the water.

How To Set Up A Gray Water System In Your Home

The ways in which to use gray water that we outlined earlier are great for keeping things simple and easy, especially if you’re just starting out with using gray water and want to get a feel for doing so.

But, there are also gray water systems that you can set up in your home with a bit of DIY expertise or (preferably) with the help of a professional.

You can set up a system that makes use of pipes which divert the water from your drains, bathroom sinks, washing machine, or bathtubs.

Just find out where the pipes coming from these sources are located, and then see the locations where you can access them before they will join the main pipes or stacks that come from the toilet, as Sciencing reports.

To do that, you’ll have to cut (or unscrew) your drain pipes and install plugs on any lower pipes.

Your new pipes will have to be connected to the upper pipes so that they will be able to collect your gray water.

Then, drilling holes will enable you to run the pipes inside the walls. You will need to fasten the pipes onto wooden supports in the walls.

You can link the pipes to a common drain pipe in your crawl space or basement. But you should install a storage tank if you’d like to make your irrigation extend over longer periods of time.

The main gray water drain pipe will then go to the storage tank. Install another pipe from the storage tank into the main drain and the sewers, or septic tank.

How Does A Gray Water System Work?

Based on the above, it’s clear to see that when water in the house comes from showers or basins, it enters pipes that lead it to the grey water tank.

It’s then stored there until it’s discharged for use, such as for irrigation or even to be put into a treatment system.

A pump is usually used to divert this water. In some cases, the use of a system that’s based on gravity can work.

In this system, there obviously has to be enough gravity (or fall) from the drains to the tank.

Taking A Closer Look At Two Types Of Gray Water Systems

Gray Water In Glass Tanks

Let’s look at two ways in which you can install a gray water system in your home: the first one is by tweaking your household plumbing so that you can divert gray water into the garden and the other one works by collecting sink water so it can be used to flush your toilet.

Gray Water System Example 1: Diverting Gray Water Into The Garden

An easy way to achieve the goal of diverting gray water into the garden is via your washing machine. This is because its pipes will be visible in your home, usually on an exterior wall.

However, you can also divert water directly from the shower or bathtub if they have accessible sink drains and pipes.

It’s easy for someone who’s interested in DIY to set up this system, mainly because the pipes are visible and/or accessible.

It does cost a bit to set up this grey water system, though – you’re looking at a price tag of approximately $300 per drain.

Gray Water System 2: Using Sink Water To Flush Toilets

If you want to use the water that goes down the sink drain in order to flush your toilet, this type of setup can be a bit expensive. That said, you can find DIY variations.

If you get this system done, you’ll need to integrate your home’s plumbing. You’ll need to maintain how the system collects and stores water, which can make it feel a bit high-maintenance.

Some systems will cost around $500, while others can cost over $1,000.

If that sounds like a hefty cost, you might just want to resort to using your own way of collecting gray water, such as by following the steps we outlined earlier.

An example includes using buckets to store gray water from basins so that you can use it to flush your toilets. It’s really simple and you don’t have to worry about burning a hole in your pocket!

But… Is Gray Water Safe?

Water Tap

Safety is one of the biggest concerns you might have when it comes to using gray water.

Even though we’ve outlined ways in which you can collect your own gray water or have it done with the use of a professional system, these concerns are still valid.

To prevent problems down the line, there are important things to bear in mind and mistakes to avoid when using gray water.

  • When setting up a gray water system, you need to ensure that you use a different plumbing system for your gray water so that you don’t risk it becoming contaminated by black water – this is the water that contains waste products. The use of a gray water pump is therefore required to remove any contaminants from black water. If done in this way, it can be safely recycled back into the home or garden.
  • Never use your untreated gray water in your lawn sprinklers. This could cause the spread of dangerous and airborne bacteria, as the International Association Of Certified Home Inspectors reports.
  • Be mindful of what you’re putting into the water, as this could affect your gray water in a negative way. For example, always make sure that you don’t use chemical detergents to clean clothing as that can make your gray water unsafe for use in the garden. Similarly, if you’re collecting gray water from the kitchen drain, you need to install a mesh strainer on it that will block food particles before they can enter the drain. Also wipe away greasy food residue from cookware and plates before you wash these in the sink. This residue doesn’t just make your gray water less hygienic, but it can block your plumbing, so it’s best avoided! 
  • Even if you’re pretty good with plumbing and DIY, you should always enlist the help of a licensed plumbing if you’re diverting your pipes to make use of gray water. This will prevent the possible cross-contamination of pipes.
  • You want to prevent any unpleasant odors that can result during the process of using gray water. A hotspot in the house where this is likely to occur is the toilet tank. If you’re putting untreated gray water into the tank of the toilet, this could lead to bad odors so it should be avoided. To be safer, put the gray water into the toilet bowl before flushing.

What About RV Gray Water?

Installing Gray Water Tank

If you have an RV, you might wonder if you can use your gray water in the same way that you would at your home.

Let’s take a look at how RV grey water and waste systems work.

In RVs, your waste doesn’t enter a city sewer treatment plant – the water enters a holding tank.

RVs have a system that’s made up of three tanks: a freshwater tank that stores water you need with which to cook and bath; a gray water tank; and a black water tank that stores your solid waste.

The first tank is the water that comes out of your taps. The gray water tank is used water from the shower and kitchen sink. Then, there’s the black water tank, which is where your human waste is stored.

Before you start toying with the idea of using your RV grey water, make sure your RV has a gray water tank!

Some RVs don’t have a tank for storing gray water and so all the dirty water from the RV will enter the black water tank. You definitely don’t want to use that water as it can contain harmful pathogens.

If you don’t drain gray water, it will become black water within a day or less, so it’s very important to drain it.

This happens as a result of bacteria setting in and it will happen faster if the weather is hot.

When draining your gray water, you can do so in various ways, such as by letting it out on the ground in a free camp, but always be considerate of people in the vicinity.

Similarly, you could be allowed to drain gray water at a caravan park, but always check with reception.

If it’s very hot or the location of the caravan park is undergoing a drought, it might be suitable to let the gray water into the gardens to hydrate the ground.

Based On The Above, Should You Recycle Your RV Gray Water?

Gray Water Holding Tank

Maybe you think it’s best not to reuse your RV’s gray water because it can be smelly, and that can be as a result of what’s been stored in it or a problem with the tank, such as a blocked vent.

However, there are ways in which you can make that gray water useful, such as for flushing your toilet.

  • First things first, you’d have to use a secondary pump that doesn’t obstruct your freshwater pump, and make use of a carbon-wrapped filter to remove particles that can release unpleasant odors in your gray water tank, as reported by RV Life.
  • There are DIY systems available that make use of a second pump to pull water from the kitchen and shower, put it in a tank, and then move it through a filtration system so that it can end up in your toilet where it can be used for flushing purposes.

RV Life provides the following steps that can help to improve your RV gray water so it can be used.

  • Make use of mesh drain strainers.. These will prevent food particles and residue from entering the drain where they can cause smelly situations.
  • Wipe down food debris from cookware and plates with a paper towel before you wash them.

Related Questions

Can you store gray water your household produces?

You can store your gray water, but not for longer than 24 hours. This is because bacteria will set in, which will lead to bad odors.

What nutrients are in gray water?

Gray water can contain nitrogen and phosphorus which can help to keep plants healthy.

Can you use gray water on grass?

You can use your gray water on grass, but as is the case with using it on your plants, you should always ensure your water doesn’t contain chemicals that are toxic to your garden.  


It’s wonderful to live more sustainably, and if you’re worried about your household’s water usage and wastage you’ll love the idea of recycling water in your home.

As we’ve seen in this article, gray water has many benefits and you can make use of it in many different ways – you don’t have to install expensive systems or play around with the plumbing if you don’t want to.

When using gray water, make sure you follow the correct safety precautions to keep yourself and your family healthy!

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