Berkeley Lake resident Frank Way was surprised to get a letter from the county the other day telling him he was going to have to pay $20 more each month in sewer charges.

Unless Way could prove he wasn't plugged in to the county system, the letter said, he'd need to start paying by May 1.

But wait a minute: Wouldn't the county already know whether he was hooked up to the sewer system?

Not necessarily, says Lynn Smarr, deputy director of Water Resources for the county.

"These are a small group of customers that could have the ability to hook up," Smarr said, "and we're just checking with them. If they have septic, that's fine. If they're not sure, we'll be glad to come out and help them. We're just doing some extra checking."

But wait: Sewer service isn't like cable, is it? Someone can't just hack into the system without anyone knowing.

Actually, Smarr said, they can. It's not a huge problem, but it has happened.

Bottom line is there's a gap in the records.

It's especially notable in some subdivisions, said Peter Frank, deputy director of systems. Say there's 15 homes, but only 13 are paying sewer bills —what happened to the other two?

The Water Resources department is trying to clean accounts up with the help of some new tools. Satellite-based GIS maps have pinpointed the county's 111 miles of sewer lines. By comparing them to customers listed in its new integrated SAP billing system, the county hopes to locate any who've slipped through the cracks.

About 6,000-7,000 letters are being sent out, said Frank, on a staggered schedule.

"We want to make sure that people who are using the system are actually paying," Frank said.

Just how many new customers the county picks up won't be clear until July, Frank said. So far, the Water Resources department has mostly heard back from folks who are on septic systems.

Until about 2001, about 58 percent of Gwinnett's single family homes were on septic systems, said Vernon Goins, spokesman for the East Metro Health District —which enforces water regulations at state, county and municipal levels. That's dropped to about 39 percent.

Way, who got his letter two days ago, said he finds the whole thing mystifying.

Last year, while installing a swimming pool in his backyard, Way considered moving from septic to sewer, he said, since a newer subdivision behind his house was on the county's system.

Turned out he couldn't.

"I had to get plats of the land, to figure out where all the properties were —and they were the ones who figured out I'd have to get an easement," Way said. "I thought it was really odd when I got a letter from them saying I could get county sewer— when it really wasn't the case for me."