Update: CBC tried to contact Ontario Safety Standards prior to the publication of this story, but did not receive a response. CBC has since been contacted by Ontario Safety Standards. The company maintains that Tom Gowe was not misled by its salespeople.

Every month for the next decade, Tom Gowe will get a costly reminder to be wary of door-to-door salespeople.

The 74-year-old Ottawa man is on the hook for monthly $65 payments for the next 10 years after signing up for what he thought was a free, government supplied water purifier.

"[I'm] very disappointed in humanity," Gowe said. "That people are still out there trying to take the seniors, and take advantage of them."

Last month, a man from an organization called Ontario Safety Standards knocked on Gowe's door and warned him there might be a problem with his tap water.

Gowe invited the man downstairs to look at his home's water tank.

When the salesperson showed him brown sediment at the bottom of the tank and told him he needed a purifier, Gowe believed him, not realizing some brown sediment was normal.

Gowe signed a contract for what he thought was a free, government-supplied purifier.

Salesperson offered same-day service

"He had called his office to see if I qualified, and of course the reply was yes, I qualified," Gowe said.

Ottawa police say once residents sign a contract, there is little they can do to help. (Stu Mills, CBC News)

The company brought a system to Gowe's home the same day.

He realized he had fallen victim to a scam two weeks later, when the first $65 bill arrived in the mail, he said.

"I was very upset. I was ready to throw [the system] out."

Gowe phoned the company to have them remove the system, but said he was hung up on the only time he got through. In addition to receiving bills, he's learned the system in his home isn't even a water purifier, but a water softener.

Tom Gowe reads over the contract he signed with Ontario Safety Standards for what he thought was a free water purifier. (Stu Mills/CBC News)

At $65 a month for 10 years, he could end up paying nearly $8,000.

"I'm upset," Gowe said. "The government should step in and do something about these door-to-door salesmen."

Think before you sign, police warn

Water, furnace, air conditioning and driveway re-sealing scams are some of the most common fraud cases, according to Ottawa police.

"Those kinds of big money decisions shouldn't be made at the door in the first place," said Sgt. Stephanie Burns.

There's little police can do once someone signs a contract, Burns said.

Waiting to think a contract over can be the best defence against pushy salespeople, she added.