Older booster systems ran pumps at full capacity part of the time and completely off the other part. Chlorinating pumps were set to run at a set rate in gallons per day, anytime the main booster pump was running. These chlorinating pumps inject chlorine into the water line prior to the flow entering a storage tank. The size of the storage tank and the rate of usage determine the amount of time the chlorine is in contact with the water before being used. The condition of the water determines the length of time chlorine must remain in contact to do the job.
Hydro pneumatic tanks have been used in the past to control the pumps as well as for contact time for chlorine. These large hydro tanks have very little draw down or usable water between pump cycles. Depending on the operating pressure a 10,000 gallon hydro tank may only have 1,200 gallons draw down. 1,200 gallons from a 10,000 gallon tank is usually not enough storage to keep pumps from cycling frequently and allows barely 1/10th of the tanks actual size to be used for chlorine contact time.
These chlorinated systems can benefit from pumping stations controlled by Cycle Stop Valves. When using Cycle Stop Valves the large hydro tanks are no longer needed. If 1,200 gallons of storage is needed for chlorine contact time then a 1,200 gallon contact tank is all that is needed. Unlike a pressure tank or hydro tank a contact tank is vented and contains no air. A 10,000 gallon hydro tank only holds 1,200 gallons of water. The remainder of the tank is either air or wasted space. A 1,200 gallon contact tank holds 1,200 gallons of water and gives that amount of contact time.
When the pump is controlled by a Cycle Stop Valve, the chlorine injector needs to be of the variable flow design. Normally a flow meter is used to measure the amount of flow produced by the pump station. This measurement controls the amount of chlorine injected. Variable flow chlorinating equipment is available for liquid or gas chlorine.
Some systems use their Cycle Stop Valve controlled pump stations to pump a chlorinated supply of water. If the water supply is chlorinated before the pump station, variable flow chlorination may not be required.