Should you wash paint rollers or throw them out?

There has been some discussion lately, whether to wash paint rollers or throw them out after a paint job. Being an eco-friendly painting company, we deal with this question often. But simply comparing the environmental impact of paint water waste, versus solid waste of a dried up roller is not an accurate comparison. As a painting contractor, we need to replace every thrown out roller with a new one. What is really the ecological footprint created by the process of manufacturing and distributing a new roller? There are raw materials to be created, transported and used, manufacturing waste, water usage, logistics and transportation for distribution etc. This discussion is about the waste water and what happens to it when it goes down the sink and treated in a water treatment facility. At the end of this discussion, what do we think is an environmentally responsible practice?

Steps in Water Treatment (by Alexandra Beek)

Water treatment plant

1. Preliminary Treatment

Preliminary Treatment is to filter out chunks so that machinery further down the line won’t get damaged. The water that is left still has a great deal of suspended solids.

2. Primary Sedimentation

The remaining sewage water is put into a sedimentation tank. Here the water has a low flow rate giving the suspended solids a chance to settle to the bottom of the tank. The removal of suspended solids in this tank are between 40% to 70%. The solids are now a sludge that is removed by a pipe at the bottom of the tank.

3. Biological Treatment

There are many different method of biological treatment, but they all revolve around a core idea. That idea is to use bacteria to eat our waste and metabolize it to less harmful products. The waste water is put into another tank along with bacteria necessary to process it. The bacteria breaks down chemicals that we pour down the sink at home, work or that industrial companies discharge into the system. Some industrial companies are food processing companies, their waste feeds the bacteria so they can take care of the hazardous waste. It’s simpler to think of bacteria as people. Biological waste is their home and for the majority of their life, their job is to work in a factory breaking down chemicals. These chemicals could be simple or very complex. The “employer wants their workers” to be working at their optimum level, so they keep the facility at a comfy temperature, open windows to let fresh air in and let their employees pig out on whatever food they want. And the final products of these chemicals are easily manageable or harmless. This step also helps the next sedimentation by coagulating the suspended solids so they settle more easily.

4. Secondary Sedimentation

Just like Primary Sedimentation but more is removed. A portion of sludge from this process is returned to the biological treatment stage to make sure the qualified bacteria keep doing the job.

5. Disinfection

Again there are a few processes that can disinfect the water but they still revolve around an idea. Kill bacteria; although bacteria was very helpful in the biological treatment stage, they are also very harmful if released into natural waterways. After disinfection the water is ready to be released into the waterways.

But what about the Sludge?

The sludge is where all the stuff is after being taken out of the water and it gets it’s own treatment. After the sludge has been removed from the primary clarifier it goes through it’s own biological treatment, sludge stabilization, to again, convert harmful compounds into less or harmless compounds. After it is stabilized the sludge has any excess water removed from it. From there it is either used in land application or is sent to a landfill (a practice not commonly utilized).

Landfill Leachate

When something is sent to the landfill, over time rain will percolate through the landfill and be collected by the leachate barriers. The leachate is collected and there will either be an onsite water treatment facility or the leachate is sent to a water treatment plant.


  • It has been common practice by some painters to wash and rinse rollers outside. By doing that, none of the water gets to go through the above treatment process.
  • Even though paint water waste is treated by many municipalities, it’s still a good idea to use as little water as possible by washing tools in containers or buckets.
  • This discussion is about washing paint rollers or not washing them, but most of this applies to washing paint brushes or other painting equipment.

Ecopainting is a painting contractor servicing the Greater Toronto Area (GTA). Contact us online for any information about our services.

Leave a Comment