When pulling water from a lake, stream or well a pump must be used to transport the water to our faucets and appliances. Mandatory for the pump is to be able to deliver sufficient pressure for enjoyable household use. The first step in designing a water system from a non-pressurized source, also called a static supply, is to size the pump properly based on the specific house in question.
Tanks make sense in both municipal and homeowner systems because without a tank, our pump will have to operate 24/7 365. It would be silly and problematic to switch on a pump every time we were going to use water. A properly designed tank and pump combination allow the pump to only come on when the tank needs filled. This saves electricity, decreases wear and tear on the pump and allows us great dependability in our water system.
Municipalities use water towers. They pump water up to the tank to fill it, and then let gravity deliver pressure when we open our faucets. Home well systems commonly use a small pressure tank with a rubber bladder inside. Instead of using gravity to deliver pressure, the pump pushes water into the bladder tank, this causes the bladder to be squeezed. Pressure builds up until a sensor shuts the pump off. Then when a faucet is opened, pressurized water is immediately available.
- A submersible pump inside the well sends water under pressure to the house.
- At the entry to the house a “T” is inserted that allows unused water to return to the well
- Right before water returns to the well it travels through something called a pressure relief valve (PRV). The PRV stays closed and does not let water return to the well until a certain pressure is achieved. This creates a backpressure in the line thereby creating line pressure inside the house.
To create adequate backpressure, it is critical that the pump be sized significantly larger than the maximum theoretical household water usage is. For example is the home can potentially use 18 gallons per minute the pump should be sized at something like 30 gpm. It is the excess capacity that allows backpressure to build. If the pump can only match maximum usage then pressure at the faucets would be very low. The downside of this system is that the pump has to run constantly.