Grey water — the water from your sink and shower — is one of the least discussed but most important parts of campervan plumbing. Filtering it keeps your tank clean, reduces smells, and helps you dispose of it legally and responsibly.
Verdict
Every van should have at least an inline mesh filter (£8) and a sink strainer. This prevents food solids from entering the grey water tank and stops smells. Add a carbon filter if you want odour control (£15). Use biodegradable soap to reduce environmental impact. The only legal disposal is at a designated grey water point.
What Is Grey Water?
Grey water is wastewater from your kitchen sink, bathroom sink, and shower. It contains soap, food particles, grease, and skin cells. It is not black water (toilet waste) — it is far less harmful — but it still contains bacteria and organic matter that decomposes and smells. In the UK, discharging grey water onto the ground or into drains without permission is technically illegal under the Environmental Protection Act 1990 and the Water Resources Act 1991. The reality is that most van lifers do it discreetly, but filtering your grey water makes it cleaner and reduces the environmental impact.
Types of Grey Water Filters
1. Inline Mesh Filter (Basic)
A simple mesh filter fitted to the sink drain pipe. It catches food particles, rice grains, tea leaves, and other solids before they enter the grey water tank. These are the same filters used in boat and caravan sinks. Best: Whale inline sink strainer (£8, from any caravan shop). It fits 28mm and 32mm pipe. Unscrew it to empty the mesh basket. Effectiveness: Catches 90% of solids. Does nothing for soap, oil, or dissolved organic matter.
2. Sink Strainer + Bowl Filter
A two-stage system: a mesh strainer in the sink plug hole catches large debris, followed by a fine mesh filter in the grey water tank inlet pipe. The fine filter catches particles down to 0.5mm. Best: Fiamma Grey Water Filter Kit (£25). Uses a 0.5mm stainless mesh. Clean it every 2-3 weeks. Effectiveness: Catches 98% of solids. The grey water tank stays nearly dry of sludge.
3. Activated Carbon Filter
An inline carbon filter that removes odours and absorbs dissolved organic compounds. These are common on boats and narrowboats. The water passes through activated carbon granules, which trap odour molecules and some chemicals. Best: SureCal Carbon Filter (£15, 10mm barb fittings). Fits inline before the grey water tank. Effectiveness: Reduces smell by 70% but does not filter solids (it clogs if solids reach it). Must be used in combination with a mesh pre-filter.
4. Full Gravity Separation System
The top-tier solution. A grey water tank with a baffle system that separates oils and grease from the water. Oil floats to the top, solids sink to the bottom, and the middle layer of relatively clean water can be discharged. Best: DIY baffle tank. A 20L water container with a vertical baffle wall (aluminium sheet sealed with Sikaflex). The inlet feeds one side, the outlet draws from the other side, and the baffle prevents oil and solids from reaching the outlet. Cost: £30-50 for materials. Fits under the van or in a storage compartment.
Installation Guide
| System | Installation Time | Difficulty | Tools Needed |
|---|---|---|---|
| Inline mesh filter | 15 minutes | Easy | Screwdriver, pipe cutter |
| Inline carbon filter | 20 minutes | Easy | Pipe cutter, jubilee clips |
| Sink strainer | 5 minutes | Very easy | None (push-fit) |
| Baffle tank | 2 hours | Medium | Drill, Sikaflex, saw |
The Legality Question
UK law is unclear on campervan grey water:
- On public land: Discharging grey water onto the ground is fly-tipping under the Environmental Protection Act. Fines can be £400-£5,000.
- On private land: Discharging grey water into a drain or onto the ground requires permission from the landowner and potentially the Environment Agency.
- At service points: Most CAMC sites, caravan parks, and motorhome service points have grey water disposal points. These are the only legal option. The filtered water argument: Filtered grey water is cleaner than unfiltered, but still contains dissolved soap and organic compounds. It is not legally clean enough to discharge without permission. The filter is about reducing your environmental impact, not getting around the law.
Eco-Friendly Options
- Biodegradable soap: Use EcoLeaf, Ecover, or Bio-D washing up liquid and soap. These contain plant-based surfactants that break down faster in the environment. They do not make grey water legal to discharge but they reduce the harm.
- Filter and carry: The most responsible approach: filter your grey water through a mesh filter into a 10L tank. When the tank is full, carry it to a service point or a household drain. Use the filtered water for flushing a cassette toilet or watering plants (if using biodegradable soap).
- The oil trap: Never pour cooking oil or grease down the sink. It solidifies in the grey water tank and turns into a solid block. Wipe pans with kitchen roll and put it in the general waste bin.
Choosing a System
| Budget | System | Cost | Maintenance |
|---|---|---|---|
| £10 | Whale inline mesh filter + sink strainer | £12 | Empty mesh every 2 weeks |
| £25 | Fiamma filter kit | £25 | Clean filter every 3 weeks |
| £40 | Mesh + carbon inline (combination) | £40 | Replace carbon every 3 months |
| £50 | DIY baffle tank | £35-50 | Drain and clean every 6 months |
