Backwash Pump Control
Backwash Pump Control
(OP)
We are designing for backwash control of a dual media rapid sand filter (18" anthracite/12" sand). We are proposing to utilize a constant speed, 7,500 gpm vertical turbine/lineshaft pump drawing from Clearwell for backwash. Backwash header will have a rate of flow controller (integral venturi/butterfly) to control backwash rate. Also proposing a blow-off on backwash header to prevent media lifting. Do we need a pump control valve on backwash pump (such as ball or cone)? What would be the advantages or alternatives?





RE: Backwash Pump Control
If you meant by "blow off" and air vent at the top of the vessel to vent of any air that may get into the unit prior to or at the same time as starting backwash then your proposal is a good one.
Gary Schreiber, CWS VI
The Purolite Co.
RE: Backwash Pump Control
Pump control valves are used where your pump is starting/stopping against a pressure head. If flow reverses through the pump, damage to pump may occur.
It is doubtful that you need a blow-off on the backwash header either. Again, the pressures that you are talking about on a filter are normally low. The design pressure of the piping system will be higher than the discharge pressures that are normally encountered.