How Our Water System Operates

Our water system operates in a fairly simple manner but in a way that may not be how you would expect. A very simplistic view of our water system would have the wells at the bottom of the system, with a water main leading to a water storage tank (essentially a big bucket at a high elevation with a loose fitting cover). Off the water main are small pipes that lead to peoples homes, these pipes end with a faucet. The well pumps water out of the ground through the pipes into the storage tank. Once the water in the water tank reaches a certain level a signal is sent to the well to stop pumping (if you didn't tell the well to stop pumping, the water would come out the top of the tank and in fact if there is a problem with the telemetering system that is exactly what happens in our system).

When someone opens their faucet in their home, the water is forced out because of the weight of the water in the storage tank sitting on top of the hill (it is the water in the storage tanks that provides the water pressure in our system). As people use water from their faucets, the water level in the storage tank drops. Once the water in the tank reaches a certain level in the tank, a signal is sent to the wells to start pumping again. Because it is the weight of the water above your faucet in your home that provides the pressure forcing the water out, the greater the elevation difference between the storage tank and your faucet, the more pressure you have (for our simplistic explanation we will ignore the effect of friction in a long run of pipe). So the homes in East Walpole (the lowest elevation in town) have the highest water pressure, and the homes next to the water tanks (the higher elevations in town), have the lowest water pressure.

Our system, is more complicated than this simplistic view but it describes the fundamental principal that it operates on. In real life, water demand is lowest in the middle of the night, picks up when everyone wakes up, levels off, then picks up again later in the day, then drops off again as people go to sleep. Our well system is set up so that we end the day with our water storage tanks completely full and our wells shut off (we actually run the Mine Brook wells continuously to avoid having to start and stop the water treatment plant, but the Washington St. wells actually shut off during the night). As people start waking and using water, the level of water in the water tanks start to drop and a signal goes out to one well to start pumping, as more people wake and water usage increase, additional wells are signaled to start pumping. At peak hours, the usage actually exceeds our ability to pump water into the system and the water level in the storage tanks slowly drops (in addition to providing the pressure to force the water out when you open a faucet, the water storage tanks provide a reserve for those short periods when the wells can't pump the water out of the ground fast enough to meet demand). Once the day draws to a close, water demand drops and one after another the wells get a signal to stop pumping.

Our water distribution system is made up of 5 pressure zones. The wells all pump water into what is known as the Central Pressure Zone (or the low pressure zone). This zone is served by the water tanks that can be seen off of High Plain St. and the Duffy tank off of Old Post Rd (this was the only pressure zone the town had until 1975). From the Central Pressure Zone, there are 4 booster pumps that force water into what are known as the High Pressure Zones.  The South High Pressure Zone (the South Walpole water tank off Summer St. serves this zone), the Old Post Rd. High Pressure Zone (the tall water tank off Old Post Rd. serves this zone), the North High Pressure Zone (the North Walpole water tank off Wagon Rd. serves this zone), and what is known as the 'Texaco' pressure zone (named because a gasoline leak at a Texaco station in Dover cause the expansion of the water system into this area which previously had been serviced by private wells). The 'Texaco' pressure zone does not have a water storage tank but has its water pressure provided by the booster station off of North St. (it is expected that at some time this situation may change and a water tank will be built in that area).