If someone knocks on your door claiming to be from the City of Calgary and wants to test your water, don't answer, the city says.

City officials say they've received more than a dozen reports through 311 and Enmax of people either representing home-service companies or claiming to be city employees.

"They'll test the water and say they need a home treatment system and recommend purchasing some of the products that their company is endorsing," said Natasha Kinloch, operations and maintenance leader for drinking water distribution with the city.

"This is a scam. It is not endorsed by the City of Calgary."

Reminder: we do not go door to door asking to test residents’ water. If someone comes to your home & identifies themselves as a City of Calgary employee, do not give them access to your home & call <a href="https://twitter.com/CalgaryPolice?ref_src=twsrc%5Etfw">@CalgaryPolice</a> at 403-266-1234 immediately. <a href="https://t.co/1DIzJ2gZHg">https://t.co/1DIzJ2gZHg</a> <a href="https://twitter.com/hashtag/yycwater?src=hash&ref_src=twsrc%5Etfw">#yycwater</a> <a href="https://t.co/8qxc6cpVZm">pic.twitter.com/8qxc6cpVZm</a> —@cityofcalgary

Kinloch said if city employees do for some reason need to test your water, they would typically call ahead and book an appointment, before showing up in a City of Calgary marked vehicle. She said all staff carry photo ID that identifies them as city employees.

So if someone shows up wanting to test your water and they aren't officially with the city, don't open the door she advised.

"We would recommend that Calgarians do not allow access to their home and call Calgary police immediately to report the activity," she said.

She also said not to worry, as Calgary's water is safe to drink.

"We have a team that closely monitors drinking water throughout the system on a daily basis. We take this commitment very seriously. And just want to make sure Calgarians are aware that our drinking water quality meets or performs better than all federal and provincial health guidelines."

If something was wrong with the city's water, it would be communicated through official channels, Kinloch said.

With files from Brooks DeCillia