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Using Gray Water in the Garden

We’ve been in situations where our area was suffering from drought conditions, with rules put in place that prohibited using city water to water our lawns, flowerbeds, or garden due to the lack of water supply. Although our lawn did have difficulties, people sometimes wondered how our garden and flowerbed flourished. There was no real secret. We used gray water.

What is meant by gray water

To understand how the use of gray water work, it is first necessary to understand what gray water is. Gray water is simply water that has been used and which would normally be poured down the drain. For example, water used for a shower or bath, washing dishes, or washing clothes is all gray water.

This water usually contains soap and possibly oils or dirt, sweat, skin flakes, hair, and so forth. It isn’t something you’d want to drink without purification and filtering. However, most plants have their own filtering system, built-in; the roots.

Using gray water

The idea behind the use of gray water is simple and straightforward. The gray water is reserved, rather than letting it flow down the drain. It is then taken out and poured around the plants in the flowerbeds or garden, after making sure that it has cooled to room temperature if it is initially hot.

There is really no more to it than this. The plants filter out what they can’t use and are able to use the water. The process is so good that it is a great way to conserve water even if drought conditions aren’t present.

Note: It isn’t legal to use gray water in all locations, so it is worthwhile to check with your town or county before trying it.

How gray water helps

It makes a lot of sense that this would be a great conservation measure that could save substantial water. The average American takes a bath or shower once per day. A shower uses around 17 gallons of water and a bath uses around 36 gallons of water. Washing dishes can account for several more gallons of water daily. The same is true for washing clothes. Just by saving all of this gray water, an average household of four could easily have 100 to 200 gallons of used water per day that could be applied to plants.

This is enough water to allow a small garden or several flowerbeds to prosper even during dry spells, all by using water that would normally be poured down the drain. In other words, it is normally wasted, though it could be used.

More water savings

A person can save even more water. Every time you boil pasta, vegetables, or what have you that would normally be drained in the sink, save that water. Once it has cooled down, it can also be used for plants. In fact, this water is even healthier for plants than tap water. It contains nutrients that the plants can use and the chlorine that is normally added to domestic water supplies is removed in the process of boiling.

A person could also use the fluid contained in cans of vegetables, which is normally poured down the drain, though care must be given in this case since it is common for salt to be added to canned vegetables and salt isn’t normally useful to plants.

What about the soap?

A person might think that soap would harm plants. However, most soap on the market breaks down into phosphates, which can be used by most plants. Phosphates are a common ingredient in fertilizers. The dead skin, sweat, and hair that comes from bathing don’t hurt, either, as it breaks down easily and furnishes nutrients for the plants.

It is quite possible to conserve water while keeping the garden, flowerbeds, and other plants watered, even during droughts. In fact, using gray water can be cost-effective, too, since you are getting a second use out of the water that you’d normally pay to replace. It is worthwhile to at least consider using gray water for your plants if you can.

This is inspired by a question by Andria Perry.


What do you think?

Written by Rex Trulove


    • I think that if I owned this place, I’d simply put in some valves in the sink drains, attached to flexible pipes leading outdoors, so I could simply switch the valve. In the winter, I’d have the valve open to use the regular sewer line. I could probably do it for all three sinks for less than $30 and I’d probably make that up in savings in less than a month.

  1. We do save some water from showers — the water we use waiting for it to get hot. I have two large wastebaskets in my shower to collect what I can as I wash, as well, but don’t have a great way to collect it all. Same in the kitchen. My sink isn’t deep enough to keep a collection basin in it when I’m rinsing dishes of washing veggies. I do use the water from boiling eggs on my plants, but I use leftover water from cooking veggies in soup.

    We also use gray water to flush toilets.

    • It sounds like you’ve given considerable thought to conserving water. That is a very good thing. Even people who live in areas that have abundant fresh water do well to conserve it. Gray water is just one means of doing it. There are many more. I really should write about how it was done in the Bible, using cisterns. It is quite fascinating, though it isn’t practical in many places today.

      • The two Republican primary candidates for California governor, neither of which probably has a chance to be elected, both want to build water storage or shore up existing dams, or both. The other party wants to tear down dams and ship water from the Sacramento Delta out to the sea to help a fish that’s not even endangered. That water would normally go to farmers. When it rains here, we do get enough water to be worth storing. I’m seriously thinking of getting some rain barrels for under the gutter spouts.

        • Just make sure that it is legal in your area. I know that in some places in California, rain is considered to be “owned” by the city, so it can’t be collected in rain barrels or otherwise used. That is absurd, of course, but some places do have laws in place about it.

    • You can usually put a stopper in the drain, then later scoop out the water. In our case, the shower and tub are one and the same, so this isn’t hard to do. For the last few years, we’ve also had a wet/dry shop-vac, too, which simplifies the scooping. lol

    • We usually have plenty of water here in Montana, too. I used this method mostly when I lived in south-central Oregon, right on the edge of the Oregon High Desert. Droughts were infrequent, but they did happen.