Like all gardeners, you will need access to water to keep your plants healthy and strong and a great way to conserve water is by collecting it when it rains. If you live in the UK you will have access to plenty of rainwater which you can collect and to do this, you may have bought a water butt. A water butt is a great way to collect all that free rainwater, meaning that you will always have a supply of water at hand in the garden but what do we do when the water is stagnant? Is stagnant water bad for plants? Or will the water be just fine?

Stagnant Pond
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Is Stagnant Water Bad for Plants?

When water is stagnant, it can often become very smelly and can harbour all sorts of nasties, some you can see and others that you cannot but, in general terms, watering your plants with stagnant water will not do them any harm at all although there are a few things to think about for before you use it. Where you live, where the water has come from and how much light the water gets can all factor in whether the stagnated water is safe to use on your plants.

Stagnant water can often be polluted or be a haven for breeding pests and have lots of microorganisms living in it.

Water Source

The water source is an important thing to consider before using water on your plants. If you have collected rainwater in a secure water butt with a lid that allows no natural light to enter, the chance of it harbouring any nasty organisms is greatly reduced. However, if the water is being collected from an old, stagnated wildlife pond, there is a much higher risk of transmitting harmful fungi and organisms that have been bred in the pond. Old pond water may also contain excess fertiliser run-off from your or your neighbour’s garden.

Where You Live

Where you live may be an important factor as to whether the stagnant water will be good for use in your garden. If you live near a heavy industrial plant or source of pollution, the water could well become contaminated with chemicals or other pollutants.


Does your water butt have a lid? You may not necessarily need one if you are cycling through water extremely quickly and the water is not sitting for any length of time. Ensuring that there is no light getting to your water can prevent the build-up of life inside meaning the water will remain cleaner. Blocking out all light will stop the growth of algae and other phytoplankton which need light to grow and survive.

By keeping the algae growth down, you are also limiting a food source for many of the other organisms or bacteria that may be lurking in your water.

Filling a Watering Can From a Water Butt
Filling a Watering Can From a Water Butt

What is Stagnant Water?

Many people think that a characteristic of stagnant water is that it is smelly and bad. This is not quite true as in fact, the term ‘stagnant water’ just means that the water is still and not flowing and there are many types of stagnant water that are perfectly safe. Bottled water is one example of stagnant water and although it has been through a filtration process making it perfectly safe to drink, it is still stagnant water (that does not mean you should start drinking water from your water butt!).

How to Stop Water from Becoming Stagnant?

There is only 1 way to ensure that water does not become stagnant and that is to keep it flowing. Any kind of constant movement whether natural like a river or artificial like a pond filtration system will keep the water from being still and therefore stagnant.

Water Butt with No Lid
Water Butt with No Lid

How to Keep Water in a Water Butt Clean?

All contained still water is stagnant water and that includes the water butt at the bottom of your garden that you are using to collect rainfall. Although stagnant water is a haven for nasties, if you employ good practice, you can keep the water reasonably clean which makes it perfect for watering your prized carrots.

Use a Lid

One of the primary ingredients of life is light. A still open water source that has plenty of light is sure to be a breeding ground for all sorts of things that you do not want. Not only is light a problem but when leaves and other organic matter get into the water and sink to the bottom, it will start to be broken down by anaerobic bacteria which can make the water become smelly.

Using a lid is very important when trying to keep water in a water butt clean.

Use a Filter

Using a filter (Amazon link – opens in a new tab) is a great way to keep the water clean. Not only will it filter out some of the organic matter to prevent it from building up it will also aerate the water and keep the water flowing.

Water that has movement or water that is being run through a filter makes the conditions less favourable to breeding organisms and insects.

Gutter-mate Filter

The award-winning gutter-mate filter (Amazon link – opens in a new tab) is a fantastic tool to add to your water collection arsenal. The gutter-mate will filter out any organic mate in the gutter before it gets a chance to reach your water butt.


Generally, people seem to think that stagnant water means that it is bad and smelly, but that is not necessarily true although people still wonder “Is stagnant water bad for plants?” Well no, all stagnant water is not bad for plants and all still water by its very definition is stagnant. What is actually bad for plants is what is contained in the water. Water that is not managed or kept clean can harbour fungi, pests and diseases that may affect the health of your plants. It is good practice to ensure that you keep your water butt clean and where possible, you should use a lid. We also recommend that you do not use water that may have been contaminated with any kind of chemicals as this is also likely to damage your plants.

Things to Consider When Collecting Water from Plants Infographic

Garden Doctor Tips

“When using a water butt, it is a good idea to keep it enclosed with a lid to prevent light and debris from getting to the water!”

“When using water from a water butt, water around your plants and not directly at the roots. By doing this, the soil will also act as a filter and remove some of the bacteria!”

“An annual clean of your water butt will prevent any build-up of organic matter, therefore, keeping down the harmful bacteria!”

“Use a gutter-mate filter to prevent any organic matter from reaching your water butt!”

Frequently Asked Questions

Is dirty water bad for plants?

This depends on what the ‘dirt’ is in the water. Water that is dirty per se is not bad for plants but if it is contaminated with chemicals then it should be disposed of. Contaminated water is very bad for your plants and when it is absorbed into the plants, it is dispersed throughout.

How long before water becomes stagnant?

All ‘still’ water is stagnant by its very definition. How long it takes to become still will depend on the water source.

If you mean, how long does it take water to become bad and smelly? There is no immediate answer, it will depend on the insects, organic debris and bacteria that may be in the water.

Can stagnant water make you sick?

All ‘still’ water is stagnant by its very definition. Water that has been bottled for consumption is an example of stagnant water but won’t make you sick. Stagnant water itself will not make you sick, what makes you sick is the harmful bacteria and organisms that will be living in the water.


Trevor Wright is not just a seasoned horticulturist; he’s the esteemed Garden Doctor. With a BSc in Horticulture and years of hands-on experience in the soil, Trevor has become a trusted mentor for all things gardening. As the founder of Garden Doctor, he’s committed to clarifying the intricacies of gardening, offering straightforward advice that’s rooted in years of practice. His writing is a garden of how-tos, savvy insights, and comprehensive guides that enable individuals to nurture and grow their garden dreams. When he’s not knee-deep in garden beds, Trevor is at his keyboard passing on his green-thumbed wisdom to budding gardeners, ensuring that the legacy of sustainable and joyful gardening blossoms far and wide.

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