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Can you use bathwater to water plants? Experts reveal how it can work wonders on your greenery

 A white bathtub filled with bubbles in a green-tiled bathroom.
A white bathtub filled with bubbles in a green-tiled bathroom.

In the midst of the cost of living crisis, every resource is precious and any opportunity to save money is welcome. So when we came across the possibility of using bathwater to water our plants, we were excited but also a little suspicious. Can you use bathwater to water plants, considering all the dirt and soap residue mixed in it?

The simple answer is – yes, you can. Despite some exceptions and precautions one should take that we’ll get into in a bit, this is one of the ways to use greywater in the garden, greywater being another name for bathwater and any other wastewater from non-toilet plumbing systems.

But to further explain why it’s safe to use bathwater on your plants, we’ve enlisted the expert help and advice of our gardening experts. Here’s what they had to say.

A blooming and growing garden with the sun shining
A blooming and growing garden with the sun shining

Can you use bathwater to water plants?

There are several benefits to using bathwater to water your plants. Firstly, it’s a way to save water and help with water supply during the summer in times of drought, water bans and shortages. And secondly, the traces of skin cells and soap can actually feed the plants, just like a natural plant fertiliser.

‘Bathwater can be good for garden plants due to its nutrient content,’ says Lucie Bradley, gardening expert at Two Wests & Elliott collaborating with Victorian Plumbing. ‘When you bathe, your water often contains traces of soap, skin cells, and even some natural oils. These elements can serve as a mild fertiliser for your plants, providing them with essential nutrients like nitrogen, phosphorus, and potassium.’

Petar Ivanov, Fantastic Gardeners' gardening expert, adds, ‘Soap and detergent can also act as wetting agents and allow water to penetrate the soil around your plants more easily by breaking up surface tension.’

Just make sure you use your bathwater within 24 hours. ‘As bacteria grows quickly, it’s wise to reuse your bathwater within 24 hours,’ says Fiona Jenkins, gardening expert at MyJobQuote.co.uk.

A white bathtub filled with bubbles in a green-tiled bathroom
A white bathtub filled with bubbles in a green-tiled bathroom

What should you be careful with?

While natural and mild soaps can be beneficial to plants due to their phosphate content also found in many fertilisers, harsh chemicals like bubble baths and synthetic soaps can be detrimental.

‘When it comes to soap and bubble baths, moderation is key,’ Lucie advises. ‘While a small amount of soap won't harm most plants, excessive use can be detrimental. Harsh chemicals in some soaps can disrupt the pH balance of the soil or coat the leaves, interfering with their ability to photosynthesize.’

Fiona then goes on to say that bathwater shouldn’t necessarily be used constantly but rather in moderation. ‘Chemicals from soaps, shampoos and bubble baths can collect in the soil, harming its microorganisms and preventing it from retaining moisture. And the salts found in bath products can stress your plants if you use bathwater over a long period of time.’

All in all, moderation is the name of the game.

A multi-leveled garden with a path and a shed
A multi-leveled garden with a path and a shed

What plants you shouldn’t use bathwater on

While most plants will react well to being watered by bathwater, there are a few that you should avoid. Including bathwater in your watering routine is not how to grow blueberries, for example.

‘While bathwater can be beneficial for most plants, there are a few exceptions. Plants with delicate foliage, such as ferns or African violets, may be more sensitive to soap residues. Additionally, plants that prefer acidic soil, like azaleas or blueberries, may not appreciate the slight alkalinity that soap can introduce,’ Lucie warns.

Additionally, Petar discourages from using bathwater on edible plants due to potential contamination and bacteria that might be harmful if eaten. ‘It's also recommended that you don't water edible plants, such as tomatoes, herbs, beans and potatoes, with your bath water.’

A blueberry bush
A blueberry bush

Can you use bathwater to water houseplants?

‘Bathwater can be used for both houseplants and garden plants alike,’ Lucie says. ‘Whether you're nurturing an indoor plant or outdoor garden, your plants can benefit from the nutrients present in bathwater. Just be mindful of the soap content and adjust accordingly.’

But due to the fact that houseplants are grown in more compact environments within a pot with a little soil, they feel the residues found in bathwater more intensely. That’s why Fiona wouldn’t recommend making a habit out of using bathwater on your houseplants.

A hallway with an open door and two large houseplants
A hallway with an open door and two large houseplants

‘As houseplants are typically contained within a small pot of soil, they will feel the effects of bathwater more acutely. So, it’s best not to water them this way. If you’re looking to save water, you could collect the cold water that runs from your shower as you wait for it to warm up.’

It turns out there are several ways how to reuse water for your plants.