In the last year, Guy Campinha, the director of the Water Pollution Control Facility, has led something of an "EDU audit" to make sure businesses and residents are paying the correct amount for waste water treatment.

He found that some businesses were paying far less than what they should according to town regulations, reigniting the discussion on revamping the way people pay for sewer usage in Wareham.

"The system didn't grow as things changed,"Selectman Alan Slavin said.

Currently, residents pay the same flat fee of $596 per property per year, according to the number of EDUs (equivalent dwelling units) assessed to a property. For example, a single-family home would be charged one EDU, while a duplex would generally be charged two EDUs.

The concept is similar for businesses. When the business grows, so too should its bill.

But according to Campinha, that hasn't been the case. He said one restaurant he checked opened years ago with five tables and today 30, meaning their EDU rating changed and the establishment should have been paying a higher bill for years.

"As these businesses increased and gained revenue, the town didn't gain revenue equally with them," Campinha said.

Selectman Patrick Tropeano presented a letter at Tuesday's Selectmen's meeting from the owner of an auto body shop whose sewer bill in 2012-13 was $1,490. He just received a bill this year for $4,768, a 320 percent increase.

The owner added two service bays to his shop ten years ago and under the EDU rate, should have been paying this increased bill since then.

"The town has been subsidizing this business for ten years," Selectman Steve Holmes said.

But Tropeano said this increase was unfair because the shop owner's water usage was likely well under the minimum, but he had to pay this high amount because of the flat fee system and other oddities in the EDU rate formula.

"Ultimately to me, we've got to change the way we do this. This system doesn't work. It's inequitable for everybody," Tropeano said.

The selectmen passed a motion to meet exclusively as the Board of Sewer Commissioners on the third selectmen meeting each month for a temporary period of time. They will only discuss sewer business and emergency selectmen agenda items at these meetings.

Only 11 percent of Massachusetts municipalities still use the flat fee system to assess waste water usage, according to Tighe and Bond, a Pocasset-based engineering and environmental consulting firm.

"We're just saying going forward let's apply the policy fairly to everybody and if we're going to change it we'll change it as time progresses," Campinha said. "But everybody is treated equally and that's what we've been doing for the last year and a half and we're doing it fairly for everybody."

Selectmen commissioned Tighe and Bond to conduct a town sewer study last May. The company's next presentation to the public will be on March 17 at 10 a.m. in the Town Hall cafeteria.

In a phone interview, Wareham Fire District Water Department Superintendent Michael Martin said the Water Department and the town have passed information back and forth for the 14 years he has been superintendent.

"We work very cooperatively and quietly with the Town," he said.

Martin added that the department provided Tighe and Bond with all the information that was asked of them as part of the consulting firm's ongoing sewer study.

"It's a two way street," Martin said. "We remain committed to assisting the Town just as they assist us when necessary."