Reusing Grey Water in the UK: A Practical Guide for Gardeners Facing Drought

Reusing Grey Water in the UK: A Practical Guide for Gardeners Facing Drought

Posted by Celtic Water on 28th Jul 2025

This summer, we’ve received a growing number of enquiries about how to reuse bath water in the garden—especially from those facing another round of hosepipe bans due to the prolonged heatwave across the UK.

If you’re in Yorkshire, the Southeast or another drought-prone area, and you're trying to keep your fruit trees, borders, or lawn alive without relying on mains water, grey water reuse could be a game-changer.

Let’s take a closer look at how to divert grey water from your bathroom, the pros and cons, and how a product like the 3P Filter Collector can help if you want to set up a simple, affordable grey water system in your garden.

What is Grey Water?

Possible design solution to filtering and diverting grey water from bathroom pipes.using the 3P Filter Collector Universal

Grey water refers to relatively clean wastewater from:

  • Baths
  • Showers
  • Bathroom sinks
  • (Occasionally) Kitchen sinks

This water can be reused safely on non-edible plants if filtered properly and used quickly, preferably near immediately and always within 24 hours.

Why Reuse Grey Water in the Garden?

Key Benefits:

  1. Water Conservation - Reduce pressure on mains supplies and lower your utility bill.
  2. Nutrient Content - Grey water often contains small amounts of nitrogen, phosphorus, and potassium—great for plants.
  3. Less Wastewater - Diverting grey water reduces the load on sewage systems and septic tanks.
  4. Eco-Friendly Gardening - A great option for those practising sustainable or permaculture gardening.

Long-Term Benefits:

  • Save hundreds of litres of water per week
  • Stay compliant with hosepipe bans
  • Reduce environmental impact
  • Keep fruit trees and ornamental gardens thriving

Grey Water Drawbacks to Keep in Mind

  1. Chemical Contamination - Non-biodegradable soaps, oils, or detergents can harm soil life and plants.
  2. Health Risks - If not handled properly, grey water can harbour and grow high concentrations of bacteria and pathogens, particularly from kitchen waters.
  3. Salt Build-Up - Some soaps and shampoos contain salts that may accumulate in the soil over time
  4. Short Storage Life - Grey water turns foul quickly—ideally use it within 6–24 hours.

How Long Can You Store Grey Water?

  • Best practice: Use immediately or within a few hours
  • Maximum: 24 hours (never more than 48)
  • After that: It becomes “black water”, unsuitable for garden use

To safely store grey water, keep it cool, sealed, and out of direct sunlight. Never store kitchen grey water unless it’s been thoroughly treated—it degrades far faster due to food waste and fats.

Why Filter Grey Water?

Even relatively clean bath or shower water contains:

  • Hair and skin particles
  • Soap scum
  • Lint and other solids

If you plan to use grey water immediately, a coarse filter is usually sufficient. But without filtration, you risk:

  • Clogging hoses or irrigation systems
  • Soil degradation

Unpleasant odours from storage tanks

The 3P Filter Collector: A Simple Grey Water Filtration Option

3P Filter Collector in BlackAlthough originally designed for rainwater harvesting, the 3P Filter Collector works well as a first-stage filter for grey water. It's ideal for those reusing low-soap bath water, especially for watering fruit trees and ornamental plants.

Features include:

  • 0.7 mm stainless-steel mesh to trap hair and debris
  • Easy-clean filter insert (important for removing soap scum and buildup)
  • Flow diverter switch to pause collection during wetter months or when required
  • Simple hose connection to water butts or tanks
  • Fits most UK downpipes (it has to be installed on a vertical pipe)

While it won’t remove bacteria or dissolve soaps, it’s an excellent coarse filter—especially for families reusing children’s bathwater, which typically contains minimal residue.

How much bath water could you expect to use?

It depends on the strength of the flow and how frequently the stainless-steel mesh filter is cleaned. The 3P Filter Collector has only been tested for rainfall from roofs. In those tests it was found that, under normal rainfall, it enables 85 to 95% of rain to be collected. The remaining water helps the debris to continue down the downpipe to your drain.

Real-World Setup Example

One customer told us:

“We’re in the Southeast and facing another likely hosepipe ban. My children bathe daily with very little soap. Right now, the water exits via a small pipe that feeds into a 70 mm pipe going to the drain. I'd love to redirect that to a water butt for my fruit trees—it’s just about figuring out the logistics.”

If your system is similar, a setup using diverter filter like the 3P Filter Collector, and a gravity-fed hose into a sealed water butt is entirely doable (or directly to the plants if you have turned the filter to the "open" position prior to emptying the bath and are very organised!)—with minimal plumbing and maximum savings.

Grey Water Safety Tips

  • Use biodegradable, plant-safe soaps
  • Don’t water edible leaves or root vegetables
  • Apply grey water at soil level, not on foliage
  • Use mulch basins to spread the water evenly
  • Rotate where you irrigate to avoid salt buildup

Did You Know?

Dick Strawbridge used a 3P Filter Collector on the BBC’s It’s Not Easy Being Green in the early 2000s to divert grey water from his bathroom into the garden. His verdict?

“It was just fine—but it did collect a lot of hair.”

Ready to Start Reusing Grey Water?

If you're looking for a UK compatible, low-maintenance solution to divert bath or shower water to your garden, the 3P Filter Collector is a smart and affordable first step. While you’ll need to clean it more frequently than when used for rainwater, it’s perfectly adaptable for grey water reuse in a garden setting.

Order the 3P Filter Collector now and start building a garden that's more resilient, sustainable, and drought-proof. it comes with 30cm of hose as standard. If you need a longer length of hose, simply order a filter collector in either Black, Grey or Brown, and a long link kit in a length of your choice up to 5m (longer lengths will need to be supported).

Note: Image shows a possible solution to filtering grey water using the 3P Filter Collector. Hoses should be supported along the wall with appropriate brackets etc if the Filter Collector is installed at any height. If in doubt consult a tradesperson or contact us with your queries.

It is highly advisable to turn the Filter Collector to the "off" position to stop diverting grey water when it's not required.