A booster pump using a Cycle Stop Valve can take the 25 PSI coming from your too short water tower and boost pressure to the 50 PSI or more if needed. Follow the scenario below.
Example with supply coming from a well field:
Two 1,000 GPM supply wells and a water tower, all in different locations, on a common or looped system feed 1,000 connections. Pressure in the system is limited by the height of the tower. Some parts of the city only receive 25 PSI. The two well pumps could be turned up to supply as much pressure as needed but the tower would overflow.
At the bottom of the water tower we attach a pump system and a manifold. This manifold includes a solenoid valve with pressure sustain to let water into the tower. This solenoid valve is controlled by the level probes in the tower or SCADA. A check valve is on a separate line that will always allow water out of the tower if, the pressure in the tower ever becomes more than the pressure in the system. The third line in the manifold contains a booster pump with a Cycle Stop Valve. This pump will boost water from the tower to a higher pressure and then into the distribution, increasing the system pressure without increasing the height of the tower. The flow from this pump is controlled by a Cycle Stop Valve, and a pressure switch attached to a 44 gallon bladder tank turns the pump on or off. The two 1,000 GPM well pumps are also both fitted with their own Cycle Stop Valves, small bladder tanks, and pressure switches.
The booster pump should supply about twice the average demand or in this case about 100 GPM. The Cycle Stop Valve on this booster pump will supply 60 PSI constantly to the distribution system, even as flow needed changes from about 3 GPM to 100 GPM. If flow needed increases above 100 GPM, the booster pump will no longer be able to keep the pressure at 60 PSI. When the system pressure drops to 55 PSI a pressure switch on one of the supply wells starts the well pump. The Cycle Stop Valve on this well pump will maintain 55 PSI on the system, adding only what extra flow is needed over what the booster pump is already supplying. If the booster pump is already supplying 100 GPM , and 120 GPM is being used in the city, then the Cycle Stop Valve will make the well pump supply only the extra 20 GPM. With both the booster pump and first well pump running a total of 1100 GPM could be used at 55 PSI. If more than 1100 GPM is needed the pressure will drop to 50 PSI and the second well pump is started. The Cycle stop Valve on the second well pump will maintain 50 PSI on the system while demand increases from 1105 GPM to 2100 GPM. When demand again decreases below 1100 GPM the Cycle Stop Valve on the first well pump will bring the system pressure up to 55 PSI, triggering a pressure switch, which is located at the second well pump, to shut the second well pump off. When the demand in the system drops below 100 GPM, the Cycle Stop Valve on the booster pump will bring the system pressure up to 60 PSI, and the other well pump will be shut off. With this many connections the booster pump should always be running, supplying from 3 GPM to 100 GPM to the system at a constant 60 PSI. Only if the system requires zero flow will the booster pump fill the 44 gallon tank to 70 PSI and be shut off.
Anytime during the operation of any or all pumps the water tower could become low. At this point the probes in the tank will signal the solenoid valve at the base of the tower to open, and also shut down the booster pump. With the tower filling and the booster pump off, the pressure will drop to 55 PSI and the first well pump will be started. If the pressure sustain feature on the solenoid valve is set to hold 54 PSI the first well pump will run at max flow until the tower is refilled. If the pressure sustain feature is set at 49 PSI, both well pumps will be running at max flow, supplying the use in the city while refilling the tower. When the tower is again full, the probes will signal the solenoid valve to close and also restart the booster pump. If demand on the system is less than 100 GPM, the Cycle Stop Valve on the booster pump will bring the system pressure up to 60 PSI, and both well pumps will be shut off.
During a power out condition, the water in the tower would still be available for emergency use, through the one-way check valve leaving the tower.
This same type set up would work with a ground storage tank instead of a water tower. The only difference being that water for emergency use during a power outage, would need to be pumped from the ground storage tank with a pump running on alternate power. A diesel powered pump or a back up generator for the electric pump could make emergency water from a ground storage tank dependable and much less expensive than an elevated tank.
If chlorination is required, use variable flow chlorine injectors at the discharge of each well pump.
Example with supply coming from a high-pressure supply line:
This type system will also work if the supply water is coming in from a high-pressure line instead of supply wells. A pressure-reducing valve on the high-pressure line can be turned up to the pressure needed in the city. Normally this higher pressure would overflow the water tower. However, in this case we will be filling the water tower through a solenoid valve. When the tower is full, a level control in the tower will open a switch, which closes the solenoid valve and stops the tower from filling any further. The city is then getting the pressure they need directly off the high-pressure line. The tower is really no longer needed except for times when the power is off. However, we need to keep the water that is in the tower from becoming stale. A small booster pump is attached to the bottom of the tower and once per day this booster pump comes on. A Cycle Stop Valve on this booster pump is set at a pressure slightly higher than the pressure of the high-pressure supply line. The booster pump lowers the level in the tower until a low level probe is reached which opens the solenoid valve to refill the tower. At the same time the low level probe opens the solenoid valve it also turns off the booster pump. This allows the city to again operate directly from the high-pressure supply line. This system will increase the pressure supplied to the city without having to increase the height of the tower. This system also keeps the tower full so if there is a power out condition, you still have a tower full of water that is supplied directly to the city through a one-way check valve. With the power off, you will still have a tower full of water to use but, it will be at a lower pressure which is dependent on the height of the tower.
