Gravity Drainage System (Roof Drainage) - Revision history

Joceil.infante at 02:59, 21 September 2017

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Joceil.infante at 03:29, 18 July 2017

2017-07-18T03:29:41Z

Joceil.infante at 03:03, 18 July 2017

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Joceil.infante: Created page with "As defined in BS EN 1253-1-2003, '''Gravity drainage system''' is a system where flow is caused by gravity and where the pipe normally operates partially full. Gravity roof d..."

2017-07-18T03:02:32Z

Created page with "As defined in BS EN 1253-1-2003, '''Gravity drainage system''' is a system where flow is caused by gravity and where the pipe normally operates partially full. Gravity roof d..."

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As defined in BS EN 1253-1-2003, '''Gravity drainage system''' is a system where flow is caused by gravity and where the pipe normally operates partially full.

Gravity roof drainage system is a drainage system that employs gravity for water to flow from the roof to the pipe system and finally to a discharge location. The fundamental design principle is open-channel without the presence of pressure.

The typical criteria to be considered in gravity roof drainage systems are;
#Water depth around the roof outlet – The capacity of gravity roof drainage system is typically limited by the water level around the roof outlets. This is because water needs to rise to a certain depth to fall through the roof outlets. [[File:Example.jpg]]
#Leaf strainer – Leaf strainers are required in most countries as it is a means to prevent foreign objects from entering the pipe system. However leaf strainers in roof outlets have a significant reduction factor to the flow rate. In accordance to BS EN 12056-3, a reduction factor of 50% has to be applied to the effective capacity of the roof outlets.
#Vertical downpipes – The important criteria for vertical downpipes is the fill rate. Most standards limits the fill rate of vertical downpipes to a maximum of 0.2 to 0.33. This is to prevent the fluctuation of pressure inside the pipes.
#Horizontal pipes (with slope) – BS EN 12056-3 allows the filling degree of maximum 70% for horizontal pipes (defined as drains which are calculated based on the principle of open channel flow). In this, the slope/gradient of the pipe is the key factor that contributes to the drainage capacity. Typical accepted gradient ranges from 1:40 to 1:100. If the gradient is not steep enough, i.e. less than 1 in 110, then the pipe could block if solids slow down and become stranded.
The design of the gravity roof drainage system has to take into consideration of the above 3 criteria and the largest diameter required by anyone of the above is adopted as the necessary pipe size for the design flow rate.
In accordance to BS EN 12056-3; it is not allowed for pipe size to reduce in the direction of flow because this will induce pressure within the pipe system.

== References ==
#BS EN 1253-1:2003
#BS EN 12056-3:2000

@@ Line 10: / Line 10: @@
 The design of the gravity roof drainage system has to take into consideration of the above 3 criteria and the largest diameter required by anyone of the above is adopted as the necessary pipe size for the design flow rate.
 In accordance to BS EN 12056-3; it is not allowed for pipe size to reduce in the direction of flow because this will induce pressure within the pipe system.
 == References ==
 #BS EN 1253-1:2003
 #BS EN 12056-3:2000

@@ Line 5: / Line 5: @@
 The typical criteria to be considered in gravity roof drainage systems are;
 #Water depth around the roof outlet – The capacity of gravity roof drainage system is typically limited by the water level around the roof outlets. This is because water needs to rise to a certain depth to fall through the roof outlets.
 #Leaf strainer – Leaf strainers are required in most countries as it is a means to prevent foreign objects from entering the pipe system. However leaf strainers in roof outlets have a significant reduction factor to the flow rate. In accordance to BS EN 12056-3, a reduction factor of 50% has to be applied to the effective capacity of the roof outlets.
 #Vertical downpipes – The important criteria for vertical downpipes is the fill rate. Most standards limits the fill rate of vertical downpipes to a maximum of 0.2 to 0.33. This is to prevent the fluctuation of pressure inside the pipes.

@@ Line 1: / Line 1: @@
-As defined in BS EN 1253-1-2003, '''Gravity drainage system''' is a system where flow is caused by gravity and where the pipe normally operates partially full.
+As defined in BS EN 1253-1-2003, Gravity drainage system is a system where flow is caused by gravity and where the pipe normally operates partially full.
 Gravity roof drainage system is a drainage system that employs gravity for water to flow from the roof to the pipe system and finally to a discharge location. The fundamental design principle is open-channel without the presence of pressure.
 The typical criteria to be considered in gravity roof drainage systems are;
-#Water depth around the roof outlet – The capacity of gravity roof drainage system is typically limited by the water level around the roof outlets. This is because water needs to rise to a certain depth to fall through the roof outlets. [[File:Example.jpg]]
+#Water depth around the roof outlet – The capacity of gravity roof drainage system is typically limited by the water level around the roof outlets. This is because water needs to rise to a certain depth to fall through the roof outlets.
 #Leaf strainer – Leaf strainers are required in most countries as it is a means to prevent foreign objects from entering the pipe system. However leaf strainers in roof outlets have a significant reduction factor to the flow rate. In accordance to BS EN 12056-3, a reduction factor of 50% has to be applied to the effective capacity of the roof outlets.
 #Vertical downpipes – The important criteria for vertical downpipes is the fill rate. Most standards limits the fill rate of vertical downpipes to a maximum of 0.2 to 0.33. This is to prevent the fluctuation of pressure inside the pipes.