pump systems for septic tanks - oregon state university

January 8, 2013 #1 Pump Systems

Pump Systems for Septic Tanks

Float Settings, Timer Settings, Pumps, and Troubleshooting

Pumps Systems January 8, 2013 #2

The Septic Tank


Common Tank Types • 1,000 gal tank • 1,500 gal tank • 1,500 gal two-compartment ∼ Spill-over or baffled ∼ Flow through


Volume Measurements • Gallons per inch ∼ 1,000 gal tank ∼ 1,500 gal tank

• Measurements for different tanks


Pump Selection • Typical application types for residential systems ∼ Pump to “d-box” ∼ Pump to pressurized system


Pump Selection • System hydraulics ∼ Head loss ∼ Gallons per minute

• Selecting the right pump


Pump Selection


Pump Selection • Select right pump for application • Note minimum liquid level


Float Switches • Operation ∼ Normally Opened vs. Normally Closed

• Types ∼ A: Normally Open, 1/8” Differential, Mercury ∼ T: Normally Closed, 1/8” Differential, Mercury

∼ B: Normally Open, 4” Differential (Typ.), Mechanical


Flow Modulation • Gravity septic tank • Demand dose vs. timed dose


Float Functions (Demand Dose) • High Water Alarm • Pump On or Pump On/Off • Pump Off • Redundant Off


Float Settings (Demand Dose) • Invert of inlet vs. outside top of tank • High Level Float • Pump On • Pump Off • Redundant Off • Pump Minimum Liquid Level • Local regulations (Oregon DEQ)


Timed Dose Advantages • Aerobic, unsaturated conditions ∼ Sand filters vs. drainfield ∼ Allows oxygen to move freely through media ∼ Complete control of dose


Float Functions (Timed Dose) • High-Level Water Alarm • Timer Override • Timer On/Off • Redundant Off


Float Settings (Timed Dose) • Surge Volume ∼ Determine daily flows from house ∼ Determine needed volume to accommodate ∼ Calculate “inches” in selected tank to match needed

surge volume


Float Settings (Timed Dose) • Invert of inlet vs. outside top of tank • High Water Alarm • Override Timer • Surge Volume • Timer On/Off • Redundant Off • Pump Minimum Liquid Level • Local Regulations (Oregon DEQ)


Timer Settings • Calculations ∼ Determine dose to drainfield

• Consult regulation • Be careful of “minimums” and “maximums”

∼ Determine flow rate of pump • Pump curve • Drawdown test


Timer Settings • Calculate “On” Time ∼ Dose vs. Flow Rate

• Calculate “Off” Time ∼ Doses Per Day


Timer Settings • Program panel ∼ Electromechanical ∼ PLC


Troubleshooting (Demand Dose) • Frequent alarms • Floats • Pump • Filter


Troubleshooting (Timed Dose) • Frequent alarms • Floats • Pump • Filter • Surge Volume


Conclusion • Successful systems must be set up correctly from start-up. • Timed dose systems work well if set up appropriately.

pump systems for septic tanks - oregon state university

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