Inspectors have been called out to 20 incidents of water pollution caused by lockdown DIY in recent weeks.
Staff from the Northern Ireland Environment Agency have investigated incidents caused by waste water linked to painting and decorating being disposed of incorrectly.
It is believed the bulk of the problems occur when people use the wrong drain to get rid of material.
There have been a number affecting the River Lagan at Dromore, County Down.
The plumes of pollution are particularly hard to trace back to their origin as they are short-lived in nature.
"The pollution we've observed is most likely the result of the wastewater associated with painting, decorating, cleaning, plastering or doing something similar, being washed into the wrong drain and straight into the nearest river," according to Environment Minister Edwin Poots.
Drains outside people's homes are known as storm drains and are designed to take rainwater and flow straight to rivers.
If people dispose of DIY or gardening waste into them, they will cause pollution.
Waste materials such as water used to clean paint brushes should be disposed of in sinks in the home.
The water from them passes through treatment works before being discharged to rivers.
Leftover paint should not be put into either drain system, but left at council recycling centres.
"I know people are taking this time to catch up on jobs around the house but please make sure disposing of the waste water associated with these DIY jobs doesn't damage your local river." Mr Poots added.
"It's important we continue to protect and respect our environment during this time and these simple measures will help do just that."