Browse Forums Building Standards; Getting It Right! Re: Downpipe Compliance - general discussion 21Dec 11, 2014 7:37 pm Posted new post as edit by mistake. Too many windows open! Original post stated that The VBA Technical Solution Sheets are guides only. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Downpipe Compliance - general discussion 22Dec 11, 2014 8:49 pm tlblhayward Question... not related to the drainpipes, but to the stormwater pipes that they are connected to. Our builder has admitted that our stormwater discharge pipe runs uphill to the legal point of discharge. The LPOD is 300mm above the stormwater pipe. How do they fix that? hmmm, might give new meaning to pushing " " uphill. We will have a similar predicament because our block slopes to the rear while the LPOD is at the front. Why? because the old drain out the rear of the property is considered a private drain so the council just wash their hands of it. In the meantime, they continue to charge $2k pa for rates with a straight face. Anyway to answer your question, if your council allows charged system, that's one option. Our council doesn't allow it, so when our storm water gets to front our property, it will have turn right along the neighbors nature strip which fortunately is downhill and hopefully reach the level the curb before we get to the end of his nature strip. This will allow us to discharge to the curb via a gravity fed system. Council will then be able to increase our rates given the increased value of the property and continue to deliver SFA. ------------------------------------------- Build Thread - Mainvue Emporio ER430 KDR https://forum.homeone.com.au/viewtopic.php?f=31&t=76790&p=1332227&hilit=mainvue#p1332227 Re: Downpipe Compliance - general discussion 23Dec 13, 2014 3:26 pm Let's look at the subsurface stormwater drainage issue. Just note that this is not my line of work but the calculations are easy. It is another area of common non compliance. Henley have referred you to the VBA Technical Solution Sheet 4.04 Drainage: (Below ground stormwater) to support their claims. The VBA Technical Solution Sheets are guides based on the regulations. 4.04 refers to: The Plumbing Code of Australia (PCA). AS/NZS 3500.3: Plumbing and drainage Part 3: Stormwater drainage. I do not know what the builder's claims are but I understand from another thread that your below ground stormwater pipes may have originally been shown as DN 90 mm uPVC pipes but have now being confirmed as DN 100 mm uPVC pipes. I further understand that there will be two pipes, one on either side of the house and the two pipes will converge into a single DN 100 mm uPVC pipe that will discharge to a LPOD. Your roof space area is 280.58 sq m. The roof slope is 22.5 degrees. Your roof catchment area factored for wind driven rain is 331.0844 sq m. AS 3500.3 Melbourne 120 ARI is 130 mm/hr, based on a 5 minute average intensity of 2.1666mm/minute. Because the two buried DN 100 mm uPVC pipes will service downpipes on separate sides of the house, one pipe will collect more water than the other during wind driven rain but I don't know what roof areas the downpipes draining to each pipe will service. The 331.0844 roof catchment area is calculated as collecting 331.0844 x 2.1666 = 717.32746 litres of rain per minute during a 1:20 ARI. Note that the total roof area only harvests water from the roof space (plan) area but the calculations are calculated on the roof catchment area (331.0844 sq m) for the reasons explained above. Below ground DN 90 mm and 100 mm stormwater pipes require a minimum 1:100 trenched gradient and the DN 90mm is rated as having a maximum hydraulic flow of 360 litres per minute with a 1:100 gradient. For your roof catchment area, two DN 100 mm uPVC pipes are a better choice than two DN 90 mm uPVC pipes. AS/NZS 3500.3 Section 5 Surface Drainage Systems-Design uses a formula found at 5.4.8(d) to determine the design flows. It is complicated but I will PM it to you along with the explanatory information. Also note that the run off from non roofed areas draining to the buried stormwater pipes must also be included in the calculations. The surface drainage coefficient varies for the difference between pervious and impervious surfaces. Using the formula is technically accurate but it also gives you 4 and 5 decimal point figures like the ones you were supplied and I have been using. The applicable Standards also have hydraulic flow charts for different types of pipe because each pipe has a different roughness coefficient and the Colebrook-White roughness coefficient is used. The table used for uPVC pipe is below. It can be found on the net by Googling the correct terms. k = 0.015 mm at the bottom refers to the Colebrook-White roughness coefficient. If you look at the darker lines on the chart, you will see the bottom dark line notated as DN 90. The point where the bottom of that line stops is about the intersect of 100 (see numeral values at the bottom) and 6 on the LHS. This represents a hydraulic flow capacity for DN 90 mm plastic pipe of about 6 litres per second (360 litres per minute) when laid with a 1:100 gradient. You will also notice that the larger pipes (except DN 100) are laid with less gradient. The DN 100 pipe's line intersects at about the intersect with 8 (lps) on the LHS with the 1:100 gradient. This is 480 litres per minute. Note that this is more than the 450 lpm that I have previously referenced for AS2200...I don't have access to AS2200 at the moment and the figures used above are not to be taken as accurate absolute. My copy of AS2200 is also not current and I am relying on memory as per the 450 lpm figure for DN 100 with a 1:100 gradient. Nevertheless, your roof catchment area is calculated to collect about 717 litres per minute during a 1:20 Melbourne ARI. Two DN 100 mm pipes connecting to a single DN 100 mm pipe will create a bottle neck because the water will not flow through the single DN 100 mm at the required flow rate and this will result in the excess discharging through a surcharge outlet such as a pit or drain. Unless a council restriction or similar exists that prevents you from draining the total amount of water from your roof to the LPOD, then the pit will surcharge at a rain intensity less than that of a 1:20 ARI if the two DN 100 mm pipes connect to a single DN 100 mm pipe. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Downpipe Compliance - general discussion 24Dec 13, 2014 7:10 pm I assume your calculation is general method under AS3500? I notice AS3500 has nominal method, under this method, they don't need to calculate all this? but under nominal method, clause 7.3.4 DN150 should be used between pits? Re: Downpipe Compliance - general discussion 25Dec 18, 2014 5:00 pm Today we received the proposal from PD to fix the drainage issues that we have been 'flooded with' since site start. If you have the knowledge/qualifications to give me accurate advice please do because I really don't want to get this wrong. Please don't make uneducated comments. http://bendigowaldorf.blogspot.com.au/2 ... eived.html Re: Downpipe Compliance - general discussion 26Dec 20, 2014 7:32 pm Henley's engineer has contacted our council and our LPOD is actually only 100mm pipe, so our pipe will not be bigger than that. em. very interesting. not sure if I should contact council myself. Council only use 5 years ARI rather than 20 years Re: Downpipe Compliance - general discussion 27Dec 24, 2014 10:33 pm Thanks to SaveH20 I have been able to create a step by step calculation to work out how many downpipes I need. Use it as a guide if you want to do it yourself. http://bendigowaldorf.blogspot.com/2014 ... ement.html Re: Downpipe Compliance - general discussion 28Dec 24, 2014 10:59 pm If anyone wants to download t"AS3500- Stormwater Drainage" then please visit the Law Resource website... https://law.resource.org/pub/nz/ibr/as- ... 3.2003.pdf I already know that the document says that it is from the New Zealand government, however the standards are the same for both countries (which is explained a few pages into the document), except in a few locations which are clearly noted. Re: Downpipe Compliance - general discussion 29Dec 28, 2014 11:58 pm Just to elaborate further on the Victorian roof stormwater drainage regulations and some builders 'errantly' using the BCA Deemed To Satisfy (DTS) provision..... As previously stated, there is a Victorian variation within the PCA under Part D1 to remove the BCA as a DTS requirement for roof drainage installations. The BCA was developed to replace local and State regulations and evolved to a performance based document about 15 years ago. In 2008, the PCA (2004 edition) was adopted into the Plumbing Regulations (2008). The PCA (2004 edition) made no reference to the BCA as a DTS provision for roof drainage systems. On May 1 2011, the PCA was introduced into the National Construction Code (NCC) as Volume 3. At the time of adoption, Victoria introduced a variation into the DTS provisions of Part D1 to exclude the BCA as a DTS provision for roof drainage systems. Note: The National Construction Code (NCC) brings together the Building Code of Australia (BCA) volumes 1 & 2 and the Plumbing Code of Australia (PCA) volume 3. Since 2011, there have been no changes made to the Victorian variation contained within Part D1 of the PCA and it currently still excludes the BCA as a provision of Part D1 of the PCA. In other words, Victoria has at no time adopted the BCA as a DTS provision for roof drainage systems. The BCA DTS provision for roof stormwater drainage is inferior to AS/NZS 3500.3 Plumbing and drainage Part 3: Stormwater drainage and the variation to exclude the BCA as a DTS provision for roof drainage systems was IMHO a wise decision. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Downpipe Compliance - general discussion 30Jan 13, 2015 6:18 pm SaveH20... your info about the VBA variation came in handy today. Scroll to the bottom of the following blog post to read about how it came in useful. http://bendigowaldorf.blogspot.com/2015 ... ction.html Re: Downpipe Compliance - general discussion 31Jan 13, 2015 10:03 pm tlblhayward SaveH20... your info about the VBA variation came in handy today. Scroll to the bottom of the following blog post to read about how it came in useful. On your blog, you posted: "As we got to talking about how they are calculated it was explained to me that downpipes are spaced with the BCA requirements of maximum 12m between them." That sounds very much like 'someone' simply positioned the downpipes no more than 12 metres apart (a non mandatory BCA requirement not found in the AS) with no calculations made whatsoever to determine the maximum compliant roof collection area drained to each downpipe. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Downpipe Compliance - general discussion 32Jan 13, 2015 10:11 pm SaveH2O tlblhayward SaveH20... your info about the VBA variation came in handy today. Scroll to the bottom of the following blog post to read about how it came in useful. On your blog, you posted: "As we got to talking about how they are calculated it was explained to me that downpipes are spaced with the BCA requirements of maximum 12m between them." That sounds very much like 'someone' simply positioned the downpipes no more than 12 metres apart (a non mandatory BCA requirement not found in the AS) with no calculations made whatsoever to determine the maximum compliant roof collection area drained to each downpipe. I knew that would get your attention! I very quickly put the person back into their box and send them the documentation! Re: Downpipe Compliance - general discussion 33Jan 14, 2015 2:40 am This should interest a few. Storm water (roof) drainage compliance does not guarantee good design, in fact, a good design may not necessarily be compliant. An example of a very common bad design that is nevertheless (often) still compliant can be seen in the photo below. Who's going first with some answers? 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Downpipe Compliance - general discussion 34Jan 14, 2015 7:16 am Let me try... 1. Sections of roof that drain to a lower section of roof must be included in the calculation for the drainage needs of the lower roof area. 2. Run-off from walls must be included in drainage design 3. There are inadequate downpipes on the Garage Re: Downpipe Compliance - general discussion 35Jan 14, 2015 11:14 am tlblhayward 1. Sections of roof that drain to a lower section of roof must be included in the calculation for the drainage needs of the lower roof area. 2. Run-off from walls must be included in drainage design Both of the above are correct but let's assume that both calculations were included in the roof drainage design as required by the regulations and the roof area harvested is compliant. tlblhayward 3. There are inadequate downpipes on the Garage Very close. You cannot see a downpipe but the downpipe is frequently at the end of the gutter (LHS in this instance) and often around the corner. I will try to get a better photo when I have time. BAD DESIGN: (previous photo) A downpipe drains an upper roof area to a spreader that discharges the highly concentrated flow to a small section of gutter on the RHS. The water hitting the abutting wall during wind driven rain travels as a concentrated flow down the wall - garage roof intersect to the end of the gutter on the RHS. Logically, the downpipe should be fitted at the gutter's RHS but because aesthetics often subjugate function, the builder/architect/designer will position the downpipe away from the front to maximise the street appeal. This is a common 'trick' used on display homes but the "design" is then carried over to the customer's house. The result is that during heavy rain, the gutter will overflow where the concentrated flow discharges to the gutter. I see it all the time. Compliant?...YES. Good design?...NO. The photo below shows good design. Not too hard to do...and it still looks good! 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Downpipe Compliance - general discussion 37May 18, 2015 10:11 am tlb, because the plans you have posted do not show the gutter's high points, the harvested area of roof that each individual downpipe drains cannot be determined. Each individual roof area harvested to each downpipe must be compliant with each State's applicable regulations but compliance is ignored by numerous builders in Victoria when they use the technically inferior and cheaper to install BCA alternative solution. As per what I have already posted in this thread, Victorian roof drainage compliance is clear cut: SaveH2O "Plumbing practitioners in Victoria are required to install roof drainage installations in accordance with AS/NZS 3500.3 Plumbing and drainage Part 3: Stormwater drainage the relevant section of AS/NZS 3500.5 Plumbing and drainage Part 5: Housing installations as prescribed in the National Construction Code Volume Three - Plumbing Code of Australia (PCA) along with HB39 – 1997 Installation code for metal roofing and wall cladding and SAA/SNZ HB114:1998 Guidelines for the design of eaves and box gutters as prescribed within the Plumbing Regulations 2008. This is as a result of the VBA implementing a Victorian variation within the PCA under Part D1to remove the BCA as a Deemed to Satisfy requirement for roof drainage installations." SaveH2O The BCA was developed to replace local and State regulations and evolved to a performance based document about 15 years ago. In 2008, the PCA (2004 edition) was adopted into the Plumbing Regulations (2008). The PCA (2004 edition) made no reference to the BCA as a DTS provision for roof drainage systems. On May 1 2011, the PCA was introduced into the National Construction Code (NCC) as Volume 3. At the time of adoption, Victoria introduced a variation into the DTS provisions of Part D1 to exclude the BCA as a DTS provision for roof drainage systems. Note: The National Construction Code (NCC) brings together the Building Code of Australia (BCA) volumes 1 & 2 and the Plumbing Code of Australia (PCA) volume 3. Since 2011, there have been no changes made to the Victorian variation contained within Part D1 of the PCA and it currently still excludes the BCA as a provision of Part D1 of the PCA. In other words, Victoria has at no time adopted the BCA as a DTS provision for roof drainage systems. The BCA DTS provision for roof stormwater drainage is inferior to AS/NZS 3500.3 Plumbing and drainage Part 3: Stormwater drainage and the variation to exclude the BCA as a DTS provision for roof drainage systems was IMHO a wise decision. The BCA deemed to satisfy solution is technically inferior and I have also explained why in this thread. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Re: Downpipe Compliance - general discussion 38May 18, 2015 11:07 am Thanks SaveH20... words of wisdom (as per usual!). Re: Downpipe Compliance - general discussion 39May 20, 2015 8:05 pm I have a proposed dwelling to be built by Simonds homes. Building in Wollert Melbourne in Aurora Estate. 223.4 square metres floor area but have 450mm eaves all round, colourbond with 25 degree pitch. I will assume the proposed guttering will be the standard and so will the downpipes. I have 7 downpipes on the plan I have but the final plans and engineering of slab and drains are not complete. Soil test and land contour survey being conducted in the next week or so. So seven downpipes, am I looking ok at this amount or will I require additional? I have a PDF of all my plans but there are a number of pages and I have no idea how to break it up and just post floor plan page of the total file. Re: Downpipe Compliance - general discussion 40May 21, 2015 2:23 am Hi goody59, The roof area when looking at a house plan is the roof circumference that also includes the gutters. Because houses are usually not singularly rectangular in shape, it is not possible in this instance to state the actual roof plan area but this is easily calculated if the plans are available. Given that the floor area is 223.4 sq m and the house has 450mm eaves (plus gutters), the roof area will be considerably more than 223.4 sq m. For this exercise, I will determine the Victorian roof drainage compliance for a 223.4 sq m roof plan area with the stated 25 degree pitch roof. Downpipes are located at the gutter's low points. The gutter's high points determine the gutter slope and the roof area drained to each downpipe. Downpipes DO NOT drain equal areas of roof. The 25 degree pitch roof is subject to a multiplier of 1.23 to allow for wind driven rain that results in more rain falling on one side of the roof. This means that the example's 223.4 sq m roof is factored as 275 sq m (rounded up) when determining eaves gutter compliance. The 7 downpipes would therefore drain an average factored roof area of 39.3 sq m in our example. If the house is in the Melbourne metro area, the 1:20 ARI (used to determine eaves gutter compliance) is 130 mm per hour, based on a 5 minute rain intensity. This is an average rain intensity of 2.166 mm per minute for 5 minutes. This example will also use the commonly used 115mm quad slotted gutters that have a cross sectional area of 5,225 sq mm. The cross sectional height is taken from 10 mm below the slots. In Victoria, if you have either 100 x 50mm rectangular or 90 mm round downpipes, the maximum factored roof area that can be drained to each downpipe in a 130mm per hour ARI with the gutter, downpipe and roof pitch combination used in this example is approximately 37 sq m to be compliant. To increase the maximum roof area drained to each downpipe as per this example, larger gutters are required. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Building Standards; Getting It Right! It's all good. You can get both wye piece and the coupling with or without thread. The cost difference is negligible and means the plumber only has to carry the single… 1 4929 For anyone that comes across this issue in the future - Just did what aussieta said and found a plumber to inspect it and sign off on it. Was difficult to find someone to… 3 7037 |