RESIDENTIAL SEPTIC PUMP

SPREADSHEETSMatt Gavelek, PE

St. Joseph County Health Department

February 19th, 2014

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SpreadsheetFacts Example Benefits Going

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DESIGN POINT

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OPERATING POINT

Pump does not perform at the design point

2 Methods of Pump Selection

Two Methods Spreadsheet Facts Example Benefits Going Forward

DESIGN POINT

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OPERATING POINT

• Only need 1 calculation• Approximation• Open to interpretation• Code checks are a guess

• Many calculations• Precise• Non-debatable• Code checks are precise

Before Personal ComputersExcel Spreadsheet = No Calculations

2 Methods of Pump Selection

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• Operating Point = actual performance of system • Operating Point is the intersection of the system curve and

pump curve• The pump only operates at the Operating Point, not the

Design Point

Operating Point Method

Two Methods Spreadsheet Facts Example Benefits Going Forward

• System Curve = the pressure (head) the pump needs to push against at various flow rates.

• System Curve = graph showing the Total Head (aka System Head) for many flow rates. – Hard by hand, easy with computers

• Total Head has 3 parts:• Elevation difference• Friction loss• Desired pressure (pressurized distribution)

System Curve

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• Pump Curve = the height the pump can lift a column of liquid at certain flow rates.

• Pump Curve is specific to each pump’s design• Pump speed, motor, impeller size & shape, volute size and

shape, etc.• Pump curves are available from pump manufacturers.

Pump Curve

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Spreadsheet Facts• 3 Excel Workbooks (spreadsheets)

• Flood Dose• Pressure Trench• Elevated Sand Mound

• Takes 2-4 Minutes to input data• Requires little understanding of Excel (ver. 2007 and up)• Pre-programmed & user defined pump data

• The spreadsheet takes 7 data points from a pump curve and creates a pump curve

• Verify the Pump Curve• The curve is current with pump manufacturer’s website• Make sure the curve isn’t wavy• The R2 value should be above 0.97

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Spreadsheet Facts• 4 Worksheets (tabs)

1. “Read Me First”• User agreement & brief instructions

2. “Design Check”• Input, Analysis & Checks• Fill out tan colored cells• IAC 6-8.3• General engineering

3. “Help”• Very detailed explanation of everything!

4. Calculations• not for users

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Spreadsheet Facts• Inline Residual Head (lateral pressure)

• In Total Head equation - commonly thought of automatic 3’ of head

• Not automatic 3’, based on geometry & operating point• Actually based on three factors:

• Perforation discharge rate = Operating flow rate (gpm) / # of holes

• Hole size• Inline Residual Head is not an input for spreadsheet• The spreadsheet uses the # of holes, hole size and operating

flow rate to determine the Inline Residual Head

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Flood Dose Example• A very experienced installer submitted a Design Point Method

• 4 Bedroom - Designer picked 60 gpm from IAC Table VII range of 30-60 gpm

• Designer used 3” force main because they like larger lines for larger # of bedrooms

• Picked a pump that’s “above” the design point

Does this comply with IAC 6-8.3?

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Flood Dose Example• Input design data into Flood Dose Spreadsheet

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Flood Dose Example• Automatic Analysis

Design Point

Operating Point

Terrible Design

• Reduces pump’s life span & very inefficient

Pump’sSweet Spot

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Flood Dose Example• Automatic Code Check

• Fails IAC 6-8.3’s requirement for flow rate (Table VII).• Fails 2 general engineering checks• System curve is flat – look into a smaller force main. Try 2”

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Flood Dose Example• Use Spreadsheet, change force main size to 2”

Pump’sSweet Spot

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Flood Dose Example• Automatic Code Check = GOOD!

• Explained problem to designer/installer.

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Flood Dose ExampleOriginal Submittal Submitted Revision

• Not code compliant• Terrible design

• Reduced longevity of pump• Very inefficient

• Code compliant• Better design

• Better pump longevity• More efficient

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Benefits of Spreadsheets

• Produce Better Designs by:• Giving the spreadsheets to your contractors!

• Saves them time by eliminating re-submittals• Utilizing the operating point method – more precise• Including general engineering checks that are not in code:

• Operating point placement• Sweet spot (middle 1/2-1/3) increases life span &

efficiency as explained by Alice at IEHA’s Fall 13 Conf.• Pump run time (short run times reduce longevity)• Lateral and manifold sizing checks

• Calculating effluent velocity• Helps to keep force mains clean if velocity is above 2 ft/s• Watches out for large velocities

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Benefits of Spreadsheets

• Saves TIME! The spreadsheets:• Requires 2-4 minutes of input• Perform ALL calculations, instantly• Perform ALL checks to IAC code, instantly

• Flood Dose = 5 checks• Pressure Trench = 8 checks• Elevated Sand Mound = 14 checks

• Recommends solutions (“Tips”) when code is not met

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Benefits of Spreadsheets

• Education• Gives users a working knowledge of pump hydraulics.• Help page is HELPFUL! Here are excerpts:

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Going Forward

• Consider using the spreadsheets in your county• These spreadsheets are free and for the public• Recommend distribution to contractors• ISDH will email the spreadsheets to LHDs• Spreadsheets & videos will be posted here:

http://www.stjosephcountyindiana.com/departments/sjchd/spreadsheets.htm• For spreadsheet questions, see the “Help” tab• 99% of questions will be answered by the “Help” tab• Otherwise, contact Alice Quinn (alquinn@isdh.in.gov)

• The Sump & Sewage Pump Manufacturers Association (SSPMA) provided comments which were implemented into the spreadsheets.

• Special THANKS to Marc Nelson (St. Joe Env. Director), Dr. Don Jones & Alice Quinn

Two Methods Spreadsheet Facts Example Benefits Going Forward

QUESTIONS or COMMENTS ??