Occasionally after using our water, the lines seem to get over pressurized and starts to drip out of the sink faucet. I'll hear it dripping and open the valve, then the flow rate is really high for a few seconds and tapers off to normal pressure. I'm assuming it comes from the cold water side because it also happens when I use our refrigerators water dispenser. The over pressure has been happening for the last year or so but the dripping from the faucet started about a month ago so I'm worried that it's getting worse. I'm on city water in the US, house was built in 1968, the only shit off is at the meter. Any idea what the problem might be? Do I need a plumber or call the water service?