MIAMI (Reuters) - Florida scam artists told elderly victims the government had changed the laws regulating toilet paper and that their septic tanks would be ruined unless they bought specially formulated rolls, court documents said.

"Through this scheme, some elderly customers were defrauded into purchasing more than 70 years worth of toilet paper," federal prosecutors in Miami said in a news release.

Three defendants pleaded guilty this week to charges of conspiring to commit wire fraud, part of what prosecutors said was a $1 million scheme to sell unnecessary septic tank products.

Mary Moore, Joseph Nouerand and Christopher Lincoln, all residents of Palm Beach County, were sales representatives for FBK Products LLC. They could face up to 20 years in prison at a sentencing set for February 10, but are likely to get shorter terms in exchange for helping prosecute three other alleged co-conspirators.

They admitted that in phone calls targeting elderly people with septic tanks, they falsely claimed their company was the only one licensed by the Environmental Protection Agency to sell a $199 "Septic Remedy" that would eliminate septic sludge and make it unnecessary to pump out the tanks.

Those who bought the product were placed on an "idiot list" for follow-up sales, court documents said.

Later, they were falsely told the laws regulating toilet paper, soap and detergent formulas had changed and that they needed to buy a new version of the septic tank treatment, as well as special toilet paper, court documents said.

If they did not, they were told, their septic tanks would not pass federal inspection and they would have to spend "beaucoup thousands to get the system up to standard."

In fact, the EPA does not license septic tank treatments or regulate septic tank products, prosecutors noted.

At least 15 people from around the United States fell victim to the fraud, court documents said.

The case is No 9:11-cr-80172-KLR.

(Reporting by Jane Sutton, editing by Jackie Frank)