The city of Gatineau imposed a ban on external use of water on Wednesday in response to both lower reservoir levels and increased usage. (CBC)

The City of Gatineau has banned residents from using water outside for their homes or businesses after increased demand during the current heat wave.

City officials said on Wednesday a lack of rain and higher temperatures have led to unusually low water levels in the city reservoirs.

Weekend temperatures that climbed above 30 C led to an overflow of consumption, and the city's water treatment plants have struggled to keep reservoirs at an acceptable level.

City of Gatineau spokesman Alain d'Entremont said the ban covers any external use of water, including filling pools, outdoor cleaning and watering gardens or lawns.

Homeowners caught breaking the ban face fines starting at $250, while businesses face fines beginning at $500.

D'Entremont said the city is also asking residents to curb indoor usage if possible and "take a quick shower instead of a bath."

The city said residents used over 110 million litres of water on Tuesday alone. That number is high for this time of year but low compared to peak summer levels, when Gatineau residents use from 660 to 880 litres per person, or close to 200 million litres in total.

Hull faces water supply issue

Meanwhile, the federal government sent more than 10,000 workers in the Hull sector of Gatineau home early on Wednesday afternoon because of a water supply issue.

Officials say a city worker was trying reroute water in an attempt to address the low levels of water in city reservoirs, and accidentally added air to the water pipes.

The water shortage meant the air conditioning units in the Place du Portage complex weren't operable. The federal government has a policy of shutting its offices if it can't keep them within a certain temperature range, so it shut down the offices and sent the workers home.

Workers are being asked to phone in early Thursday morning to find out whether the offices will be open.

Officials at the Collège Saint-Joseph de Hull, just a few kilometres away, also closed the private all-girl's high school on Wednesday after discovering brown water in their taps.

The school reported it to the city, which recommended the school shut its doors for the day.

Officials are asking Gatineau residents to run their water for a few minutes if it looks or tastes strange.

The problems came as the temperature in Gatineau reached 34 C on Wednesday, with the humidex making it feel closer to 40.