Changes

In some practices, such as [[bioretention]], [[swales]] or [[stormwater planters]], the flow limiting component is usually the [[filter media]]. In other, usually underground practices such as [[infiltration trenches]], [[infiltration chambers]], and [[exfiltration trenches]], the [[pipe]] will be the primary flow limiting component.  

In practices such as [[bioretention]], [[bioswales]] or [[stormwater planters]], the flow limiting component is usually the [[filter media]]. See [[Flow through media]] page for guidance in estimating the maximum flow rate through bioretention filter media.  In underground practices such as [[infiltration trenches]], [[infiltration chambers]], and [[exfiltration trenches]], the perforated [[pipe]] that delivers water to the practice will be the primary flow limiting component.  

Manufacturers of perforated pipe are often able to provide the open area per meter length. Where this information is not directly available, the open area can be calculated by measuring the perforations and summing the open area per meter. The maximum flow rate through a perforated pipe (''Q_{max, pipe}'', m³/s) is calculated similarly to [[flow through an orifice]]:  

 

Manufacturers of perforated pipe are often able to provide the open area per meter length. Where this information is not directly available, the open area can be calculated by measuring the perforations and summing the open area per meter. The maximum flow rate through a perforated pipe (''Q_{max, pipe}'', m³/s) may be calculated as:  

<math>Q_{max, pipe}=L\times B\times C_{d}\times A_{o}\sqrt{2\cdot g\cdot h_{max}}</math>

<math>Q_{max, pipe}=L\times B\times C_{d}\times A_{o}\sqrt{2\cdot g\cdot h_{max}}</math>

===Note===

===Note===

Whilst it is recognised that many smaller perforations present a greater resistance to flow than fewer, larger perforations<ref>Pabst, M., & France, J. (n.d.). GETTING WATER INTO PIPES -NOT AS EASY AS IT SEEMS. Retrieved from http://dnrc.mt.gov/divisions/water/operations/docs/dam-safety/technical-references/getting_water_into_pipes.pdf</ref>, calibrating for this is quite complex <ref>Hazenberg, G., and U. S. Panu (1991), Theoretical analysis of flow rate into perforated drain tubes, Water Resour. Res., 27(7), 1411–1418, doi:10.1029/91WR00779.</ref><ref>Murphy, P. (n.d.). THE HYDRAULIC PERFORMANCE OF PERFORATED PIPE UNDER-DRAINS SURROUNDED BY LOOSE AGGREGATE. Retrieved from http://tigerprints.clemson.edu/all_theses</ref>. The practice of approximating, using the open area of the pipe per unit length, is commonplace, and we are unaware of ill effects arising<ref>Department of Planning and Local Government South Australia. (2010). Water Sensitive Urban Design Technical Manual Greater Adelaide Region Bioretention Systems for Streetscapes. Adelaide. Retrieved from https://www.sa.gov.au/__data/assets/pdf_file/0010/19837/WSUD_chapter_10.pdf</ref><ref>ADS pipe. (2004). Outflow from Perforated Pipe. Retrieved March 12, 2018, from http://discountdrainage.com/dev/wp-content/uploads/Technical_Note_2.105_Outflow_From_Perforated_Pipe.pdf</ref><ref>Titan Industries Inc. (n.d.). To Calculate the Amount of Water Flow (GPM) Through Slotted PVC Well Screen. Retrieved from http://www.titanpipe.com/Engineering_Titan_Industries_In/Water Flow PVC Well Screen.pdf</ref><ref>WaveRail. (n.d.). WATER WELL SCREEN &amp; CASING SYSTEMS. Retrieved March 12, 2018, from http://www.waverail.nl/images/Template_content/PDF/documentatie/Filter-buizen.pdf</ref>.

While it is recognised that many smaller perforations present a greater resistance to flow than fewer, larger perforations<ref>Pabst, M., & France, J. (n.d.). GETTING WATER INTO PIPES -NOT AS EASY AS IT SEEMS. Retrieved from http://dnrc.mt.gov/divisions/water/operations/docs/dam-safety/technical-references/getting_water_into_pipes.pdf</ref>, calibrating for this is quite complex <ref>Hazenberg, G., and U. S. Panu (1991), Theoretical analysis of flow rate into perforated drain tubes, Water Resour. Res., 27(7), 1411–1418, doi:10.1029/91WR00779.</ref><ref>Murphy, P. (n.d.). THE HYDRAULIC PERFORMANCE OF PERFORATED PIPE UNDER-DRAINS SURROUNDED BY LOOSE AGGREGATE. Retrieved from http://tigerprints.clemson.edu/all_theses</ref>. The practice of approximating, using the open area of the pipe per unit length, is commonplace, and we are unaware of ill effects arising<ref>Department of Planning and Local Government South Australia. (2010). Water Sensitive Urban Design Technical Manual Greater Adelaide Region Bioretention Systems for Streetscapes. Adelaide. Retrieved from https://www.sa.gov.au/__data/assets/pdf_file/0010/19837/WSUD_chapter_10.pdf</ref><ref>ADS pipe. (2004). Outflow from Perforated Pipe. Retrieved March 12, 2018, from http://discountdrainage.com/dev/wp-content/uploads/Technical_Note_2.105_Outflow_From_Perforated_Pipe.pdf</ref><ref>Titan Industries Inc. (n.d.). To Calculate the Amount of Water Flow (GPM) Through Slotted PVC Well Screen. Retrieved from http://www.titanpipe.com/Engineering_Titan_Industries_In/Water Flow PVC Well Screen.pdf</ref><ref>WaveRail. (n.d.). WATER WELL SCREEN &amp; CASING SYSTEMS. Retrieved March 12, 2018, from http://www.waverail.nl/images/Template_content/PDF/documentatie/Filter-buizen.pdf</ref>.

 

 

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[[category:Calculations]]

[[category:Calculations]]