Why sink-washing paint brushes is a problem
A single brush washed under running water can waste 15–30 litres of fresh water — and along with it, a mix of:
- Microplastics from the paint's polymer binders (paint is now recognized as one of the largest sources of ocean microplastics — larger than plastic bottles and bags combined, according to a widely cited 2022 study).
- Heavy metals like lead, cadmium, and chromium, present in some pigments.
- VOCs (volatile organic compounds), which can evaporate into air or dissolve into water, both harmful to aquatic life.
- Biocides and surfactants, added to paint to prevent microbial growth and improve spreadability — toxic to fish in even small concentrations.
Water treatment facilities are built to handle sewage, not paint chemicals. Most of what goes down the drain during brush-washing passes straight through and ends up in waterways.
Is it different for water-based (latex) paint?
Slightly — but not enough to make it safe. Water-based paints are generally less toxic than oil-based paints, meaning the immediate handling risk is lower. But they still contain the same microplastic-forming polymers and pigments. "Water-based" describes the solvent, not the environmental impact of what's suspended in it.
Is it OK to rinse a little paint off in the sink?
Even a light rinse adds up. If every painter rinses "just a little" after every brush, that's still tens of thousands of litres of contaminated water per city, per year. A Swedish painter cleaning brushes weekly is estimated to send around 200 litres of contaminated water down the drain — and with roughly 15,000 professional painters in Sweden alone, that's over 100 million litres a year from one country.
What to do instead
- Use up the paint first. Before cleaning, apply as much paint as possible to the project rather than leaving it on the brush.
- Wipe, don't rinse. Remove excess paint with a rag or paper towel before any water touches the brush.
- Use a closed cleaning system. A paint brush washer — like Lavabrush — cleans brushes in a sealed container instead of under running water. This is the biggest single change: it turns an open, uncontrolled process into a closed one where the wastewater can be collected and disposed of properly, instead of going straight down the drain. Lavabrush cleans up to 15 brushes with just 1.5 litres of water total (compared to 15–30 litres per brush under a tap), and the used water stays contained until you drain and recycle it correctly.
- Dispose of wash water properly. Let paint particles settle, then take the sludge/solvent to a household hazardous waste facility rather than pouring it anywhere — sink, sewer, or yard.
- For oil-based paint specifically, always use a solvent-based cleaner in a sealed container, never water, and always dispose of the used solvent at a hazardous waste facility.
The bottom line
Washing paint brushes in the sink — even briefly, even with water-based paint — sends microplastics and paint chemicals into the water system where treatment plants can't fully catch them. The fix isn't to stop cleaning your brushes properly; it's to stop doing it under an open tap. A closed-system brush cleaner like Lavabrush gets brushes just as clean (often in under 30 seconds) while keeping the wastewater contained and disposal responsible.