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Any type of pressure system can be designed using our latest GTO Engineering Spreadsheets.

The pump choice is determined in only a few minutes using our spreadsheets. 


Introduction to the Use of GTO Septic Design

 Engineering Spreadsheets


image of the GTO Spreadsheet used to calculate friction losses of all the pipes and lines in a pressurized septic systemWelcome: Designing every septic system containing a pump requires some way of calculating the demands of your system to determine which of the hundreds of pumps out there will work best for you. Some pump manufacturers offer free programs to calculate which of their pumps would work for your system, but it only works with their brand of pumps.  

The GTO (Generic Treatment Option) spreadsheets will work with everyone's pumps. GTO spreadsheets are ideal for all single-family homes, small lakefront cottages, commercial buildings and larger systems for apartments, condominiums and churches. The calculations are also required by local health departments to accompany your plans when applying for a permit to construct a pressurized septic system.

The GTO spreadsheets come in the format, Windows Excel currently in use everywhere. Any reasonably current spreadsheet program will be able to import and use them.

By inserting the details of your system's information into all the pale yellow boxes, you will be able to determine what pump is needed for your job plus other system details. Once you have inserted your data, the two darker grey boxes near the middle bottom of Page 2 shown here, give you the pump characteristics you must have to operate your system.

All pumps have only two main characteristics that must match your system. These are the output volume in gallons per minute (GPM) and the output pressure expressed as total dynamic head (TDH.)

Head Loss is based on Lateral Design: First open and fill out the pale yellow boxes in the �Head Loss� spreadsheet. The details of the lateral design include lateral pipe type, pipe diameter, orifice diameter, orifice spacing and orifice number. These details of the lateral design are required on your plans to be approved by the local health department. This will yield the output characteristics for the lateral in GPM (gallons per minute.) Multiplying the lateral output by the number of laterals will yield the total system output in GPM.  Examine the Badger Lateral Design below.

illustration of a typical lateral design from a plan set

Friction and Other Losses: The second spreadsheet is filled in to predict the total dynamic head of your system. The second sheet involves three losses. First the losses from the friction of the water moving through the pipes, secondly the losses from lifting the effluent up to the drainfield plus thirdly, the excess head or squirt height. Your plans must show the elevation of the low water in the pump chamber and the elevation of the highest lateral in scale. The datum point elevation must be shown (usually 0 and the top of the pump chamber), the pump-off elevation and the elevation of the laterals are all required for inputting on Page 2 of the spreadsheets.

Check out this typical cross-section below from the Badger system.

image of a septic system cross section showing all the relevent system components

If this is your first time working with spreadsheets, don't worry. Just follow our detailed instructions. Fill in the blanks and let the spreadsheet do all the work. The instructions are very clear. From the results of the calculations you can pick the perfect pump to run your system. By accurately measuring all of your losses with the spreadsheets, you will be able to ensure a long life for the pump and perhaps recognition over time of a good design.

Advanced users of the spreadsheets can solve for designs using compound transport lines. By combining two different diameters over the total length of the line, you can reach almost any backpressure. Pumps work best when the head pressure generally matches the published output of the pump.

Advanced users will also be able to design systems using duplex, triplex and quad pumping systems. The spreadsheets allow breaking down large drainfields into multiple smaller segments.

Advanced users will discover that the spreadsheets work out the pump run times and pump off times for systems utilizing timed dosing.

If you choose our products, you will recognize their value. These products are designed to take advantage of the computer technology that we all have at our hands. Our products are designed to save your time, and to make you look good.

John Glassco, Software Developer & owner Eco-nomic Inc.

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Last Revised: 11/11/2016

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