Bathwater, also known as greywater, can total an average of 25 gallons per bath – sometimes even more – which makes baths less eco-friendly than quick showers. But if you have a large tub or don’t have access to a shower, how can you make your bathing more environmentally friendly?
Recycling your bathwater is a great way to cut down on your water usage. You can reuse bathwater for washing your car, sharing it with someone else in your household, or watering your plants.
If you want to recycle your bathwater, make sure to use natural disinfectants, personal care products, and deodorants to cut down on synthetic chemicals.
What happens to bathwater after you’re done with your bath?
Once you’re out of the bath, the water flows down the drain and travels to the sewer, where it is then transported to a treatment plant where it can be cleaned, filtered, and chemically processed. Clean water is then recycled into the main water system or released into the environment.
That’s the basic version applicable to most countries.
In the UK, all water from baths, sinks, toilets, and washing machines are carried away by pipes into a sewage treatment center where it will be treated.
After treatment, the water is released into rivers and streams. The process is regulated by the Environmental Agency to make sure it’s as safe as possible.
During treatment, the water undergoes these processes:
- Large objects like nappies, face wipes, and sanitary products (none of which should be flushed down toilets!) are removed
- Settlement tanks allow other waste to sink to the bottom, so the water is separated from solids
- As much waste is removed as possible
- Air is pumped into the tanks to allow bacteria to break down harmful bacteria
- The remaining bacteria is removed
- Then the water is released back into the environment
Different US states treat water differently, though most are regulated by the Environmental Protection Agency and state agencies.
According to the Clean Water Act, wastewater is treated by:
- Removing coarse solids
- Screened to remove floating objects like rags, bottles, sticks, and cans
- Put through a grit chamber so sand, grit, cinders, and small stones settle at the bottom
- Sedimentation tanks slow down the wastewater so floating particles sink
- Secondary treatment processes like attached growth and suspended growth treatments remove 90% of the organic matter using biological treatment processes
- The wastewater then goes into a man-made lagoon where algae, bacteria, and oxygen improve water quality
All wastewater treatments use a combination of biological and chemical treatments, though these can vary across treatment centers. Common chemical treatments include disinfecting with chlorine, ozone, or ultraviolet radiation.
Does bath water get reused?
Whether your bathwater is treated and then released into the environment or treated and cycled back into drinking water, the good news is that it will be reused!
However, the treated wastewater undergoes can be potentially damaging to the environment, because chlorine, ozone, and ultraviolet radiation levels in water can hurt marine life.
Why should you recycle your bathwater?
The chemicals used at municipal wastewater treatment plants can be harmful to organisms and humans.
A 2003 study in Poland found that the chemical and biological hazards found in wastewater treatment plants affected the health of its workers.
They included heavy metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, volatile organic matter, hydrogen sulfide, endotoxins, glucans, bacteria, viruses, and fungi.
Sludge, which is made up of the sedimented small particles in wastewater, is often disposed of on land, and it potentially contains “different types of pathogens and heavy metals which can [cause] pollution of surface and ground waters, soils and spread diseases“.
Across the world, around 80% of wastewater is released into the environment without adequate treatment.
When wastewater isn’t properly disposed of, wastewater discharge can pollute rivers which potentially causes “an increase in biological oxygen demand, chemical oxygen demand, total dissolved solids, and total suspended solids”.
This includes toxic metals like cadmium, chromium, nickel, and lead – making the water unsafe for drinking, irrigation, aquatic life, and even human health.
While you’d hope your bathwater doesn’t contain any of the above chemicals, it’s possible for small amounts to be contained.
As for other chemicals, chlorine is already present in your bathwater due to treatment facilities.
Recycling your greywater from a bath is a great way of reducing the amount of pollutants in the environment’s water systems. It also helps you be aware of exactly what your greywater might contain, so you can make an informed decision on how to recycle it.
Can you recycle and reuse bathwater?
Recycling your bathwater can be as easy as using a bucket. Even a bucket of greywater can help reduce your water usage – like using it for watering your plants.
Instead of pouring fresh water from a tap, using greywater can reduce how much water you use without actually cutting down on anything.
There are five main methods of collecting your greywater to be reused.
- First, the bucket method. It’s cheap and easy, but it’s also very manual. Simply get a bucket or container you already own and scoop out as much tub water as you can.
- A pond pump is another method, where you use a pond pump attached to a garden hose to remove the water from your bathtub. This might be a bit tricky if your bathtub is up some stairs though!
- A diverter valve in the pipeline can redirect your bathwater to where you want to store it. Make sure to use a plumber! Alternatively, you can insert a diverter valve and air pump in the pipeline.
- The most expensive method is the best for households who run a lot of baths or have a large garden. A greywater tank can drain bathwater into a separate tank, filter it, treat it, and then diverts the water for reuse.
- There are also greywater systems you can have installed which recycle greywater for flushing toilets.
You should investigate all your options and plan how exactly you want to use your greywater before making a commitment.
While recycling bathwater is ideal for reducing water usage and being more sustainable, planning will save you time, effort, and money by allowing you to know exactly what kind of system you need.
You can also collect water from your shower if you leave it on to warm up!
Can you filter and reuse bathwater?
A basic filter can catch small debris that might be in the water like hair and dirt. This can make it cleaner for your plants.
While you can filter your bathwater, I wouldn’t advise using it as drinking water. Bathwater already contains chlorine, which can be filtered by water conditioning systems or shower filters.
Greywater systems usually contain filters to remove debris like hair and grease, but it might not filter chlorine. It’s best to be clear with your suppliers or plumber to ensure you’re getting the filter you want.
Vitamin C can neutralize chlorine in water. By adding a quarter of a teaspoon of sodium ascorbate into the bathwater 5 minutes before bathing, you can neutralize the chlorine and chloramine.
You can also buy faucet filters to use on your bathtub taps to remove as many chemicals as possible. You can then use an ordinary water filter to remove bacteria, chemicals, and metals.
How do you recycle bathwater?
Remember to always be careful about what hygiene, beauty, and cleaning products you use. Swap to natural products to reduce the amount of potentially toxic synthetic chemicals and metals introduced into your bathwater.
Disinfecting your bathtub with water and vinegar or a homemade scouring powder will ensure you use natural ingredients.
Once you’ve figured out how to collect your bathwater – or maybe you’re trying the bucket method out first – make sure to filter it to catch as much debris and bacteria as possible. Then it’s time to use it!
The most common uses of greywater are for:
- Washing cars
- Watering your garden
Some US states have standards or laws to regulate greywater use and systems, so make sure of the laws in your area.
Can I use bathwater to water my garden?
The Royal Horticultural Society experimented with greywater for several weeks and found that using greywater for up to 6 weeks with no tap water didn’t “significantly affect plant function”. Rinsing with tap water occasionally is good to avoid salt stress in plants.
Can you use bathwater on your vegetable garden?
Greywater can be used for your vegetable garden provided you make sure that you’re not introducing any harmful chemicals to the plants or soil.
If you use any synthetic chemicals and they make it into the water, you could damage your plants or even give yourself food poisoning!
Make sure to test your plants’ tolerance to bathwater before committing to a system, or consult a professional garden.
Can you reuse bathwater to flush the toilet?
You can pour bathwater down your toilet bowl to flush it instead of using fresh water from the tank.
This means the water will still go down to be treated, but it saves already treated water from being wasted.
Is it safe to share bathwater?
Reusing bathwater should be okay provided nobody using the water has any contagious diseases or skin conditions and only natural hygiene products are used.
It’s not the most hygienic due to skin cells and dirt collecting in the tub, but the water dilutes it and most dirt remains on you until you dry off with a towel.
Essentially, compare it to sitting in a Jacuzzi with other people. If you’re comfortable with sharing your bathwater, why not?
Are there any other ways you can reuse bathwater?
If your bathwater is clean enough, you could use it to manually clean clothes, bedding, or other fabrics.
Cleaning fabrics in colder water releases fewer microfibers from your clothes.
You definitely shouldn’t try to reuse your greywater for watering plants or you might introduce microfibers into your garden!