Browse Forums Building Standards; Getting It Right! Re: Correct Roof Drainage Design Issues AS3500 vs HB35 2Sep 22, 2016 2:57 pm 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: Correct Roof Drainage Design Issues AS3500 vs HB35 4Sep 24, 2016 3:23 pm 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: Correct Roof Drainage Design Issues AS3500 vs HB35 6Sep 27, 2016 2:59 am 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: Correct Roof Drainage Design Issues AS3500 vs HB35 8Sep 28, 2016 2:03 am jarunit Even the csiro method accounting for the straight runs seemed pretty conservative still requiring a 170mm half round gutter and 125mm downpipe. Yes...but it needs to be. You have two large roof catchments served by optimally located single downpipes but you also live in a high (200mm/hr) 1:20 ARI region plus you have a 30 degree roof slope! The house is also about 50 years old but I assume that had there been an overflow problem up to the present day, then it would already have been addressed. Roof drainage calculations, being generic, cannot take all influences into consideration for practical reasons but your situation is that if you want compliance even with the lax BCA, you either have to have an industrial size gutter and downpipe or else have a regular size gutter but two downpipes draining it at two new locations. In your situation, I would just do what will work by being clever and save some money as a bonus. jarunit I still don't understand why the half round gutters wouldn't work with the tornado rain head? I could be wrong but I can't see how they could fit. I don't think that you would need them anyway. Of interest, AS/NZS 3500.1 Section 8 Figure 8.3 shows the weir flow rate down a vertical pipe that is inverted in a tank of water. A 125mm pipe with a 20mm, 30mm and 40mm depth of water above the crest will flow at 2.21, 4.07 and 6.26 litres per second respectively. It must also be remembered that a downpipe receives flowing water. jarunit I have another more well known roofer coming to price the job on Thursday so I want to ensure I give him the right information. Should I A) 150mm half round gutter + 100mm colorbond downpipe B) 200mm half round gutter + 150mm downpipes I would go for A) but insist on a good slope. Just tell him that you want to upgrade to the half round and ask whether they can be fitted with a 100mm downpipe. The issue will be his adherence to compliance and whether he will insist on only installing a solution that is compliant as is his requirement. Also make sure that he knows the new regulations for overflow provision. What are your current gutter and downpipe sizes? jarunit And worth adding any accessories such as any rainhead/leafguards in your opinion? Flushing a mass of organic matter into the stormwater should be avoided if at all possible but I cannot recommend any of the current leaf diverters. I was working on one until a year ago and I will get back to it once my current work backlog is under control but for now it is on the back burner. I particularly don't recommend the bucket catchment type. jarunit I will have a crack at measuring the existing gutters slope. Although could the slope be adjusted when installing the new gutters? The roofer will most likely check your current gutter height on the fascia for compliance, it is called a h/f formula. This will give him an indication. A new type of gutter will have different brackets. 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: Correct Roof Drainage Design Issues AS3500 vs HB35 9Sep 28, 2016 6:41 am Thanks H20. The existing has 125mm quad gutters with 100x50 downpipes. I think I am set on the 150mm half round with 100mm colorbond downpipes. Just to be clear, in case it does fit, have you come across this "Tornado" rain head, it is not just a standard rain head but it claims to improve flow by 5 times due to vortex action it creates. Given that we are going with the 150mm gutter/100mm downpipe, it seems any additional flow we can get would be worth it. Do you think these claims have any merit, and would it be worth paying the extra to install these? Link to the product is below: http://www.tornadorainhead.com/products.html Alternatively is there anything which could improve flow at the connection between the 150mm gutter and the 100mm downpipe? Or would the standard 100mm DP fixed straight into the 150mm gutter generally be sufficient? Re: Correct Roof Drainage Design Issues AS3500 vs HB35 10Sep 28, 2016 11:38 pm jarunit The existing has 125mm quad gutters with 100x50 downpipes. Replacing like with like is the easy option but I would be 'surprised' if the gutters never overflowed during heavy rain. 100mm x 50mm downpipes are inadequate for your roof drainage requirement. jarunit I think I am set on the 150mm half round with 100mm colorbond downpipes. They will be a substantial step up with low/no maintenance benefits, a good choice. jarunit .....have you come across this "Tornado" rain head, it is not just a standard rain head but it claims to improve flow by 5 times due to vortex action it creates. Water flowing into a pipe by what is known as weir flow naturally induces an annular vortex. This is why water spirals down a round pipe and why standard downpipes never have less than 3/4 air unless blocked. Weir flow is a very inefficient drainage method because of the vortex it generates. If a large orifice drains into a smaller pipe, the smaller pipe will be flooded during heavy rain and consequently drains faster by what is referred to as bubble flow, a process with a higher % of water volume and the third of the four priming stages that purge syphonic drainage pipes of air. It is the initial larger surface area's capacity to drain more water to the smaller pipe under turbulent conditions that generates the increased flow, not the vortex. jarunit Alternatively is there anything which could improve flow at the connection between the 150mm gutter and the 100mm downpipe? Or would the standard 100mm DP fixed straight into the 150mm gutter generally be sufficient? A 100mm downpipe is more than capable of draining your gutters as per the flow rates at different heights above the crest of the overflow that I previously posted. The half round gutter is a reasonably tall gutter and the 150mm version will have plenty of reserve carrying capacity. 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: Correct Roof Drainage Design Issues AS3500 vs HB35 11Sep 29, 2016 8:21 am Thank you H20, you have cleared up alot of confusion and saved me and my family alot of heart ache. If I understand correctly regarding your comments on weir flow, you do not think it is worth spending the extra for the Tornado rain head? Should we just run with standard connection detail between the half round gutter and the downpipe ? Re: Correct Roof Drainage Design Issues AS3500 vs HB35 12Sep 29, 2016 4:17 pm jarunit If I understand correctly regarding your comments on weir flow, you do not think it is worth spending the extra for the Tornado rain head? Should we just run with standard connection detail between the half round gutter and the downpipe ? The Tornado rain head is manufactured in Australia by an Australian company, I also manufacture in Australia and I support other Australian companies who also manufacturer quality products in Australia. When I offer advice on forums, I don't recommend against a product that I might think is not needed for a particular situation in case a recommendation is interpreted as a criticism of the product itself, what I try to do is give information that will allow the reader to understand the dynamics so they can make an informed decision. I don't think that the Tornado rain head can be fitted to a half round gutter but you are best to contact the manufacturer and ask them for that information. I have checked and confirmed that half round gutters can be fitted with 100mm downpipes. The flow characteristics of a half round gutter combined with a 100mm downpipe will give superb flushing and a more than adequate drainage capacity for your straight gutters. It must be remembered that the 100mm downpipe's pop/outlet services the half round gutter's entire sole and extends up the walls. The half round gutter flows with a greater velocity in comparison to other gutters. The greater velocity and the outlet/pop's characteristics also increases the downpipe's drainage capacity due to the generated turbulence entraining air at the top of the downpipe. The Tornado rain head's larger surface interface increases the initial drainage capacity but it also significantly increases the smaller downpipe's flow capacity due to the turbulence also entraining air which induces bubble flow as previously explained. The vortex does not cause the gutter to drain faster, the gutter drains by a combination of design, slope and the size of the gutter's outlet/pop/rainhead. Reducing the vortex significantly increases the downpipe's flow capacity by allowing the downpipe to fill with more water which also flows with greater velocity due to minor head pressure being generated during bubble flow. You will see this in the Tornado rain head video. The 100mm downpipe for your gutter will also be subjected to some turbulence during heavy rain but it won't need this 'assistance' to cope. The downpipe outlet/pop should be fitted to the gutter's underside so as to eliminate the ridge that is made when the pop is fitted inside the gutter. Decaying organic matter is negatively charged and this will rust metal gutters, it is best to eliminate any possibility of sediments accumulating. Rain Harvesting Pty Lty is an Australian company that makes a 100mm uPVC outlet/pop for half round gutters and it is widely available. The part number is GSG006. A little off topic but for some other applications, the vortex can be eliminated by fitting an anti vortex baffle above the pipe to block the vortex once the water level rises above the baffle. Once the vortex is eliminated and the pipe purged of air, the water will flow vertically (not spiral) under head pressure at high velocities that generate sub atmospheric pressures. The negative pressures are greatest at the top of the pipe and the negative pressure literally sucks water into the pipe. Negative pressures can however cause pipes to buckle asymmetrically and so fit for purpose pipes must be used. The method is called syphonic (also siphonic) drainage and it is used on virtually all large roofs world wide. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. Need more photos from around the house including your gutters. We have had 3 of the wettest years in a row for some time so that wouldn't be helping 3 6959 Hi there everyone i was hoping to get some details and some clarification on some potential defects that may have occurred our recent bathroom renovation. 1. There seems… 0 6981 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 4934 |