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

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The Septic Tank

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

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

• Measurements for different tanks

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

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

• Selecting the right pump

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Pump Selection

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Pump Selection

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

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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

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

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

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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)

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

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

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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

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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)

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Timer Settings • Calculations ∼ Determine dose to drainfield

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

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

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

• Calculate “Off” Time ∼ Doses Per Day

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Timer Settings • Program panel ∼ Electromechanical ∼ PLC

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

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

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