Browse Forums General Discussion Re: Water tanks and building codes 2Apr 13, 2021 8:01 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: Water tanks and building codes 6Apr 13, 2021 9:40 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: Water tanks and building codes 9Apr 13, 2021 10:53 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: Water tanks and building codes 10Apr 13, 2021 11:21 pm SaveH2O Ozgarden Our inlet and overflow pipes are at the same height on the top edges of the tank. Hmmm! Do you mean at the top of the tank's side? Water must pass through mosquito proof mesh before entering the tank, do you have mosquito proof leaf diverters fitted to each wet system downpipe? Yes, at the top of the sides. No mesh over the inlet or overflow. No mosquito proof leaf diverters on the wet system downpipes. Whatever lands in the gutter will flow into the tank. I tooked into the gutter today and the overflowing section had 5mm deep green wet slime in it. Perhaps a low spot? The entire length doesn't seem to be washed out very well when it rains. The inlet needs to be easily removed in case the overflow mesh gums up plus provide access for desludging. There is still the manhole inlet on the top of the tank that isn't being used. The builder put the inlet into the side at the top and the same sized outlet at the same height on the other side of the tank. It must also be remembered that the outlet pipe's mosquito proof mesh barrier presents an additional considerable flow restriction. No barrier on ours. Re: Water tanks and building codes 11Apr 13, 2021 11:39 pm Do you know the gutter size and are there overflow slots in the front wall? I need to know the gutter's cross sectional area to check compliance. How old would the gutters be (need to refer back to old regs). 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: Water tanks and building codes 12Apr 14, 2021 12:11 am SaveH2O Do you know the gutter size and are there overflow slots in the front wall? I need to know the gutter's cross sectional area to check compliance. How old would the gutters be (need to refer back to old regs). Slimline quad gutter with slots. 2 years old. I'm sure the gutter is 125mm wide.This photo might help estimate the height. A lot less high than wide it seems. I can get up and actually measure it tomorrow. Forgive the mould. I've actually washed the gutter twice since we moved in and took a photo to show all the mould that has grown since all the rain recently. This is actually on the north facing side of the house. The base of the gutter should be perpendicular to the fascia shouldn't it? Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ I've been wondering why a lot of water overflows the fascia on the left side of the above photo. Today I found out. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ The water from two corrugations on the roof flow directly onto flashing and that is sloped off the side of the roof. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Re: Water tanks and building codes 13Apr 14, 2021 11:52 am https://cdn.dcs.lysaght.com/download/quad-115-hi-front-xl-slotted-gutter-technical-guide Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ I am sure it is this gutter. 115mm wide. I tried to measure how far up the slots are and it is about 55mm. The downpipes are painted so using a tape measure I estimated they are 90mm external diameter. The pipe they go into and is part of the riser to the tank is 110mm external diameter. The three downpipes across the house are all 90mm too. The overflow from the tank and the three front downpipes must all go into a 110mm diameter pipe as I measured the diameter of the pipe coming up in the drainage pit where all the water ends up. I also realised the pipes going into and out of the tank might create a bottleneck. This is the inlet from the closed system pipe from the back gutter. They reduced the 110 to 90 towards the top of the riser. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Overflow Originally the elbow at the top of both of these was just held in place with silicon and only protruded a cm into the tank. When the tank did finally fill it popped both pipes out. So the plumber came back and was only going to resilicon over the top of the old stuff and stick them back in. I suggested he do something better. I asked about screens for the inlet and overflow but I just get ignored each time I ask such questions. There are none anywhere. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Re: Water tanks and building codes 14Apr 14, 2021 11:50 pm I"ll address your concerns as a segmented block answer and also try to explain and reference the regulations so that you understand them. I cannot however help addressing the answer below that you received from the builder! Ozgarden Anyway, after all our gutters were overflowing yet again last week we wrote again to the builder and got this answer back. "If the water tank is full, the water in the gutters will have no where to go as the downpipes will be full and so they will overflow. If you’ve not tried emptying the tank when it rains, maybe try that?" Doesn't the builder know that water tank has an overflow fitted that is required to handle this situation? This goes on the list of the most ridiculous things that I have heard. HOUSE ROOF AREA: Total roof area: 278.3 sq m. 3 downpipes service the front roof area of 148.5 sq m. 2 downpipes service the back roof area of 129.8 sq m. These downpipes divert to the tank via a wet system. IF the downpipes each drained equal roof harvest areas, each downpipe would service 64.9 sq m. Roof drainage compliance factors the regions 1:20 Average Recurrence Interval (ARI) with the roof catchment areas drained to each downpipe to arrive at the gutter and downpipe size. The rainfall intensity is based on a 5 minute minimum average which is then referred to as an hourly figure but it is the 5 minute average duration that is noted. NOTE: The National Construction Code comprises the Building Code of Australia (BCA) Volumes one and 2 and the Plumbing Code of Australia which is Volume 3. The BCA, being the primary document, has hierarchy over referenced Deemed To Satisfy (DTS) Australian Standards AS/NZS 3500.3 Plumbing and drainage Stormwater drainage. I mention this because the BCA stormwater regulations are laxer than the AS, so much so that Victoria where I am based has never recognised the BCA for stormwater regulations. The BCA does however at times defer to AS/NZS 3500.3. Your stormwater regulations are based on the BCA Volume 2 regs found at 3.5.3 Gutters and downpipes. If you want a digital copy of the BCA Volume 2, just PM me your Email and I will send it. BUNDABERG 1:20 ARI: 265 mm/hr as per BCA Volume 2 3.5.3.1d This is a 5 minute minimum average duration of 4.4 mm/min. By comparison, the Bundaberg AS 1:20 ARI looks to be 310 mm/hr or 5.2 mm/min. Roof areas are also factored with a slope multiplier to account for wind driven rain but I won't do this due to the minor slope. The minimum average rainfall (BCA) over a 5 minute 1:20 ARI duration on the house roof is 278.3 (sq m) x 4.4 (mm/min) = 1,224.5 litres per minute (lpm). The minimum average rainfall (BCA) over a 5 minute 1:20 ARI duration on the back roof is 129.8 (sq m) x 4.4 (mm/min) = 571.1 litres per minute (lpm). This equates to a velocity through the 100mm DWV pipe of 1.12 metres per second (m/sec) which is well within its scope. WATER TANK FACTS: All water tank openings must be mosquito proof meshed. Mosquito proof mesh has apertures less than 1,000 microns (1 mm). You are required to have mosquito proof leaf diverters (aka rain heads) fitted to the top of each wet system downpipe. None are fitted. These regulations should also be found under QLD Health regulations. You are also required to have first flush diverters fitted. None are fitted. The wet system reduces from a 110mm Outside Diameter (OD) DWV pipe to a 90mm OD stormwater pipe so that it fits the 90mm inlet. The respective Internal Diameters of the two pipes are 104mm and 86.2mm, the DWV having 46% more volume. Water will flow through the 90mm wet system inlet with a minimum average velocity of 1.65 m/sec which is not good but it doesn't breach compliance. TANK OVERFLOW PIPE: The tank overflow pipe cannot be sized to apply a flow restriction and a horizontal outlet is much less efficient than a standing vertical pipe. Let's say you had a 100mm horizontal overflow outlet, the flow rate with 100mm of water above the pipe's invert (the bottom of the pipe) would be 280 lpm which is a lot less than the 571 lpm inflow during a minimum 1:20 ARI. With water 125mm and 150mm above the invert, the flow rates would be 343 and 396 lpm...or would they??? You see, those are figures for an unmeshed outlet whereas your outlet is required to be meshed! You should see now why the 90mm outlet, even without mesh, is totally inadequate. There are ways to increase the efficiency of an overflow pipe, I can post that information later. WET SYSTEM: The pipe run is about 30 m + the pipe fittings and flow restriction at the tank inlet which are expressed as equivalent additional pipe lengths. This would easily make the pipe length equivalent to +50 metres and the greater the velocity, the greater the friction loss. Such systems need competent hydraulic calculations and it is very, very obvious that this wasn't done. ROOF DRAINAGE SYSTEM: The BCA Volume 2 roof drainage calculations that determine your minimum gutter and downpipe sizes start at Table 3.5.3.2a GUTTERS: I will not paste the NCC (BCA) charts due to copyright but if the two downpipe servicing the back roof area were draining roughly equal roof catchment areas, we would consult the left hand column with an ARI of <275 mm/hr. The prior column is 255 mm/hr and so your 265 mm/hr defers to 275 mm/hr. We then move along the top column to a roof catchment area of <70 sq m and it states that a type F size gutter is required. You will also note that for your 1:20 ARI, a type F gutter is required for a 1:20 ARI of 200 mm/hr or greater and so your gutter size needed for compliance is well in excess of your standard gutter IN ALL AREAS of the house. Your gutters are probably 125mm quad, having 115mm quad is way, way beyond the realms of possibility even for these clowns. A Type F gutter is noted in the BCA as "Gutter must be designed in accordance with AS/NZS 3500.3". It will be a big gutter but there really should be more downpipes and certainly an extra one between the two downpipes at the back. This will require the gutter to also be resloped as the middle section will currently be the gutter's high point. You also need to find out the size of the pipe that joins the two 100mm DWV pipe runs and is plumbed to the LPOD. DOWNPIPES: Your description of ponding indicates that the gutters need resloping. The downpipes at the front are well positioned but it is possible that the gutter's mid point is also its low point, the gutter's slope needs to be checked. The overflow could however be caused by having a 100mm DWV pipe run all the way to the LPOD. As per the NCC Volume 2, the gutter and downpipe size is deferred to AS 3500.3 specs and the 90mm downpipes DO NOT cut it. As a quick, easy to plumb and inexpensive interim solution to the overflowing gutters, you could fit some of my Gutter Pumpers. You just need to know where you will drain them to but you may need a detention tank. https://www.gutterpumper.com.au/ The builder, plumber and certifier need to be reported to their respective regulatory bodies and a forensic investigation of your stormwater plumbing urgently requested. 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: Water tanks and building codes 15Apr 15, 2021 8:22 am Ozgarden Our back gutter is the worst. It is a charged (closed) system to a tank he installed. Three times he had to repair the underground stormwater pipe to the tank in the first year because they kept leaking. One time a join fell apart in their hands and obviously hadn't been glued at all during the original installation. At the time he said it was our fault because we decided after he'd put the pipes in to add a tank and that put extra pressure on pipes that weren't designed to hold it, 'there's pressure, and then there's pressure.' The first two times the builder and his apprentices cut apart the joins and repaired them with rubber boots to cover the gaps, with stainless steel straps at each end. The third time the plumber came and said one problem was a pipe being installed 'back to front.' Apparently it was all caused originally by the builder's bobcat running over the area and squashing the pipe a bit, causing the joins to leak. I couldn't make sense of this the first few times that I read it but I now suspect that he was possibly/probably referring to the pipe flowing with reverse slope along one section. If so and while this makes no difference to the hydraulic head, it will foster a build up of crud that will result is a further flow restriction. Having the pipe slopes checked is a particularly critical matter due to there being no leaf diverters fitted to the downpipes. 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: Water tanks and building codes 17Apr 15, 2021 10:48 am This is going up on my Wall Of Infamy. BTW, NCC Volume 2 3.5.3.5 states: "Downpipes must - (a) not serve more than 12 m of gutter length for 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: Water tanks and building codes 19Apr 15, 2021 11:06 am SaveH2O This is going up on my Wall Of Infamy. BTW, NCC Volume 2 3.5.3.5 states: "Downpipes must - (a) not serve more than 12 m of gutter length for each downpipe". I've seen that quoted all the time on other forums then people all argue about the interpretation of it. People say that can mean that if you have a 24m gutter you still only need a downpipe at each end so each only serves 12m. Re: Water tanks and building codes 20Apr 15, 2021 1:00 pm Ozgarden People say that can mean that if you have a 24m gutter you still only need a downpipe at each end so each only serves 12m. That is correct and it is something that I have posted many times to point out the absurdity of the reg. Suitably sloping such a gutter would result in a large height variance between the gutter's mid way high point and the low points at the downpipes. This in turn encourages fitting a minimal slope which then has slow water flow and an inadequate flushing capability. The 'brains' that be who are responsible for the poor BCA stormwater regs have also changed the wording several times. Prior to May 2007, the Building Code of Australia (BCA) stated: The spacing between downpipes must not be more than 12 m. This was revised on the 1st of May, 2007 to... “3.5.2.5 Downpipes - size and installation Downpipes must - (a) not serve more than 12m of gutter length for each downpipe; and (b) be located as close as possible to valley gutters and, if the downpipe is more than 1.2m from a valley, provision for overflow must be made to the gutter; and (c) be selected in accordance with the appropriate eaves gutter section as shown in Tables 3.5.2.2.” In effect, the above meant that two downpipes each serving 12 metres of gutter could be fitted at either end of a 24 metre long verandah, i.e., 24 metres apart. It also confused building surveyors and others because many thought that the gutter length served defined compliance, not adherence to the maximum allowable roof area drained. On May 1 2013, the BCA was amended to once again state "The spacing between downpipes must not be more than 12 m." And of course it has flopped again to the current regulation. Downpipes are invariably poorly positioned for aesthetics rather than function in any case yet still be compliant with the regs. This is why so many downpipes are fitted at the end of walls. There are also no (common sense) regulations requiring downpipes to be fitted to a section of lower storey gutter that an upper story downpipe discharges to via a tiny spreader. It is common to see an upper storey downpipe discharging a concentrated flow of water to the end of a gutter on a garage roof that has the downpipe fitted around the corner on the blind side. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Aesthetics subjugating function! And of course why not have NO downpipes at the front as part of the tidy up? Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. That was always going to be a challenge and a test of patience. Full marks to your mate. Did you discuss the wet area near the trampoline? 16 18331 I want to build a decking to the drawn shape outlined in black. The problem is how close can I build to the gas hot water unit? Will I be able to build around it and be… 0 20671 |