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Chlorinating with Variable Flow Systems
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 determines 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.
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