Short answer: Paint-contaminated brush-washing water should not be poured into a sink, sewer or storm drain. Even water-based paint leaves paint residue in the wash water. Keep that water contained and follow the paint label, safety data sheet and your local waste authority’s instructions.
Why paint-brush wash water should not go down the sink
Many water-based paints use synthetic polymer binders. The European Commission reports that paints are, on average, 37% plastic-polymer-based and identifies paint as a significant source of microplastic releases. A Swedish Environmental Protection Agency report also cites an estimate that cleaning painting tools in private consumption may release around 240 tonnes of polymer material into Swedish wastewater each year, while explicitly noting uncertainty about how much meets the study’s microplastics definition.
Paint formulations differ. Depending on the product, wash water can also contain pigments, preservatives, surfactants and other additives. This is why the precise disposal instruction should come from the product label, its safety data sheet and the relevant local waste authority—not from the fact that a paint is described as water-based.
How much water does brush cleaning use?
In Lavabrush comparative testing, cleaning a brush under running water used 15–30 litres per brush. Lavabrush uses 1.5 litres of water per fill to clean 7–15 brushes, with each brush taking around 30 seconds. Under the tested comparison, this represents up to 99% less water. Actual results can vary with brush size, paint load, tap flow and cleaning technique.
At an estimated 200 litres per painter per week, 15,000 painters would use about 138 million litres of water per year for brush cleaning, based on 46 working weeks (200 × 15,000 × 46). This is an illustrative estimate based on those assumptions, not a measured national total.
Is water-based paint different?
Water-based paint is designed to be cleaned with water, but that does not make paint-contaminated wash water suitable for the drain. “Water-based” describes the carrier used in the paint; it does not mean that every ingredient in the resulting wash water is harmless or readily removed by wastewater treatment.
Is a small rinse acceptable?
A small rinse still transfers paint residue into the wastewater system. The practical rule is simple: minimise the paint left on the brush, avoid an open running tap and keep the wash water contained for appropriate handling.
How to clean paint brushes without using the sink
- Use the remaining paint. Work as much paint as possible from the brush onto the intended surface.
- Remove excess paint. Wipe or scrape the brush in accordance with the paint manufacturer’s instructions before washing.
- Use a contained cleaning system. Lavabrush is a professional paint brush cleaner designed for brushes used with water-based paint. It keeps the cleaning water in the unit instead of sending it directly down an open drain.
- Follow the operating guidance. See the Lavabrush instructions for setup, cleaning, water changes and maintenance.
- Handle used wash water correctly. Keep it contained and follow the paint label, safety data sheet and local rules. Commercial painting waste may be subject to different requirements from household waste.
For a practical alternative, follow our guide to cleaning paint brushes professionally. You can also see how much water conventional paint-brush cleaning can use.
The bottom line
Do not wash paint brushes directly in the sink. A contained process gives professional painters control over both water use and the resulting wash water. Lavabrush’s measurable performance claim is specific: 1.5 litres per fill for 7–15 brushes, around 30 seconds per brush and up to 99% less water under the tested comparison—not a general claim that the entire product has no environmental impact.
For more practical answers, read the professional paint brush cleaning FAQ or view the Lavabrush paint brush cleaner.
Sources and substantiation
- European Commission staff working document on unintentional microplastic releases
- Swedish Environmental Protection Agency, Report 6973: Mapping plastic flows in the construction sector
- Lavabrush water-use, capacity and cleaning-time figures are supported by Lavabrush controlled performance testing.