PVC Pipe Stormwater - 90mm or 100mm? Plumbing Supplies
- The slope of the pipe effects the flow rate. So it is not simply the case a 100mm stormwater pipe will always have a greater flow rate than a 90mm stormwater pipe
- For extra rigidity it makes sense to go fro a HDPE pipe as opposed to a PVC pipe. It will cost more but it is extremely hard to break a HDPE pipe and it will simply deform. You can also think of using a DWV pipe (Drain Waste & Vent pipe). The DWV pipe is made of sewer grade PVC and is much stronger than stormwater PVC
- The question really is about catering to the Annual exceedance probability. This refers to the probability that a given total rainfall over a given duration will be exceeded in any one year.
- A 100 mm stormwater pipe has 20% greater capacity than a 90mm stormwater pipe. Therefore it all depends on how much water the pipe is catching, where you live regarding rain intensity and the risk of flooding in your dwelling due to overflowing.
- The best solution we reached was - AS3500.3 states that you need to design for a AEP 1% for box gutters and 5% for eaves gutters. If this is your stormwater drainage for a house, there's a very high chance it's going to be eaves gutter.
Google BOM IFD and input the coordinates of your building. Multiply the AEP (mm/hr) by the roof area and divide by 3600 to get your total flow rate for the roof. Once you calculated that, you can then select the correct size pipe. You will also need 600mm of cover over your pipe if it's a trafficable area.
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