Boosting from One Pump Station to Another
Boosting water from one place to another can be easily controlled using Cycle Stop Valves. Following are a few examples of how to pump in series using Cycle Stop Valves.
A rural water system as an example has 170 miles of pipelines and supplies only 140 connections scattered throughout this distance. Two water wells supply a total of 700 GPM to feed the system. The wells pump a short distance to a storage tank then a duplex pump system draws from this storage and boost to 90 PSI. This booster sends water about 10 miles to another storage tank and booster pump. The second booster sends water another 10 miles to a third storage tank and booster pump system. The process is repeated over and over fourteen times. All along the 170 miles of pipelines there are houses randomly tapped into the line.
An old system used probes to control the level of the storage tanks. When a storage tank was full, a signal would be sent 10 miles upstream to shut off the booster pump. A low probe would send a signal to start the booster. Storage tanks would continually drain and be refilled. A major problem occurs when the booster pumps start or stop. No matter how slow you start the pump or open a control valve, the pressure would spike. Trying to get a ten mile long line of water started could not be done slowly enough to prevent pressure spikes and main line breaks. Then when the storage tank was full, turning off the booster pump would cause a dip in pressure that was followed by another water hammer. These pressure spikes were causing 300 major line breaks each year. Not just a little leak but, ripping out a forty foot section of 8" pipe and a roadway.
The Cycle Stop Valve solution was to keep the flow moving. Equipping all pumps with a Cycle Stop Valve means that the usage in the system is continuously matched. The inlet of each storage tanks was also equipped with a special low pressure Cycle Stop Valve. The Cycle Stop Valves on the inlet of the storage tanks close down to a minimum of 5 GPM and are set at 10 PSI. This keeps a constant level of 23' in each storage tank as long as there is a demand for at least 5 GPM. If the system accidently ever went to zero flow, the storage tanks would overflow at the rate of 5 GPM, but the flow would continue to move. The wells now only supply as much water as the entire system is using. Each booster pump now supplies only the amount of flow being used downstream of that booster system. The flow in the system never stops, as the flow rate used in the system is continually matched by the Cycle Stop Valves. Flow rates in the system can vary from as little as 5 GPM to as much as 700 GPM without ever stopping the flow in any of the lines. Taps can be installed anywhere in the system from the discharge of the Cycle Stop Valves on the well pumps to the furthest line past the last booster pump. This continuous matching of the flow completely eliminates the line breaks that occur from frequent starting and stopping of the pumps.
The same system as above can be done without using the storage tanks. Each booster system can draw water directly from the end of the ten-mile water line coming from the last booster or well. Simply pick up the water at 20 PSI and boost it back up to 90 PSI sending it on down the next ten miles of pipeline. Each booster system should be fitted with a low suction pressure cut off switch. If there is not at least 10 PSI of pressure feeding the booster then that booster will not be allowed to run. This means of control eliminates the need for the storage tanks that normally feed each booster system. These tanks are not usually large enough to be of any good for storage and are only used as a buffer between the old type booster system controls. Eliminating these tanks will save on purchase cost as well as energy. The pressure feeding each booster pump is the pressure left over from the last ten miles of boosting. Depending on the usage between boosters and the friction loss at least 10 PSI and possible 50 PSI could be left over to feed the next booster pump. Boosting this water from 50 PSI to 90 PSI instead of from atmospheric pressure to 90 PSI saves considerable energy on pumping cost.
Note: Because these type systems run continuously, different size pumps are needed at each booster system to make the system efficient. A small pump can efficiently handle the small demands then a larger pump is only started when needed.