Just recently the pressure of our water in the house surges when we turn a faucet on, and the city water company verified that our pressure in the house when we open a faucet is higher than the pressure in the lines in the street, and after the water runs is at a normal pressure (meaning their pressure valve is working properly). We are also seeing a significant amount of water coming through the pressure relief valve on the hot water heater. The city water person said we could buy a surge tank to put on the hot water heater to take care of the situation. When I Google "surge tank" I do not find anything that looks correct. Is there something wrong with the hot water tank? What is a surge tank, or does it have a different name?