SWAMPSCOTT – The combined water/sewer rates for the current fiscal year have increased by approximately 5 percent from last year even though residents are using less water.Town Accountant Dave Castellarin explained water consumption in town has decreased, but rates are increasing because the water/sewer is an enterprise fund and must be self-supporting.Selectmen voted unanimously earlier this month to set the water rate at $6.40 per 100 cubic feet and to set the sewer rate at $4.99 per 100 cubic feet, which is a combined increase of 5.07 percent over last year. One hundred cubic feet of water is roughly 748 gallons.Castellarin explained rising operational costs are a factor in the rate increases for both water and sewer.He said the town receives its water from the MWRA and its sewer is pumped to Lynn.”The MWRA raised its rate for water by 3.4 percent,” Castellarin said. “Lynn Water and Sewer Commission increased the cost of handling our sewage by 6 percent.”Last year selectmen set the water rate at $6.02 per 100 cubic feet and the sewer rate at $4.82 per 100 cubic feet, which Castellarin said was an increase of approximately 13.2 percent from the previous year. He added the average annual increase in the combined water and sewer rates from FY’04 to FY’11 was an increase of 5.64 percent.A couple of years ago, the selectmen voted to impose a quarterly base fee of $19.75 for each home in town, which remains in effect. According to Castellarin, a base fee distributes the cost of operating the system more equitably because there are some residents who do not use the service for a portion of the year, which means those using the service during any given quarter bear the costs of operating the system.