Browse Forums Eco Living Re: Rain water tanks & storm run off. 21Sep 22, 2012 1:42 pm It's all in the maths. 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: Rain water tanks & storm run off. 22Sep 24, 2012 11:53 am Yep it is saveH2O,i feel better coz he is going in the direction that you are talking about,cheers kat Block bought 1st RBC X! 2nd Ventrua,Keeper! Pstart 18/7/11 Ethwks jan 2012 Slab Bricks- finished 7/6 Roof Trusses 15/6-cbond 21/7 viewtopic.php?f=31&t=41185 Re: Rain water tanks & storm run off. 23Oct 12, 2012 9:14 pm Hello, I was hoping I could get some advice in working out how many downpipes we would need to collect rainwater from our house and shed (perth hills, no scheme water). We are also hoping to conceal downpipes within each reconstituted limestone columns that support the verandah roof that runs along the front and one side of the house. Details: House (main roof) - 24m x 22m, hip roof 25 degree pitch - will have rainwater spreaders to divert water to verandah roof Front Verandah - 2.1m x 19m - 6 columns spaced 3.5m Side Verandah - 2.1m x 22m - 7 columns spaced 3.7m Garage attached to house, gable roof - 6.3m x 7.3m Shed - 15m x 20m, gable roof 14 degree pitch Tanks - 2 x 200,000 litres (rhino tanks) Planning to run 3 x 100mm pipe from house to tanks and 2 x 100mm pipes from shed. Columns will only allow a maximum 60mm size downpipe Thanks in advance. Re: Rain water tanks & storm run off. 24Oct 12, 2012 11:51 pm HOUSE - 528 sq m. The multiplier for the 25 degree pitch is 1.23, giving a calculation area of 650 sq m. FRONT VERANDAH - 40 sq m. The pitch is unknown but I assume it is fairly flat. SIDE VERANDAH - 46 sq m. The pitch is as above. GARAGE - 46 sq m. A multiplier would give you 57 sq m. SHED - 300 sq m. The 14 degree pitch has a multiplier of 1.12 which gives 336 sq m but shed roof drainage is not regulated as far as I know unless things have recently changed. The number of downpipes depends on the 1:20 ARI (Perth is an average of 2.5 mm per minute over a 5 minute duration), the size of downpipe, the type of gutter (I assume eaves gutters but are they slotted?), the gutter's cross sectional area and the slope. Calculations can only be based on this information. The roof drainage area must also include the exposed gutter area. There are a number of online roof drainage calculators available. You just type in the information where required and the maximum roof area serving one downpipe will come up. Note that the maximum roof drainage area is never able to be practically used. Slotted gutters also serve smaller roof harvest areas. The gutter manufacturers also list their gutter's effective cross sectional areas. Note that information on some gutter and downpipe manufacturers websites re permissible roof harvest areas is often wrong! Re the verandah's limestone columns requiring a maximum downpipe diameter of 60 mm, you would actually be looking at a 65 mm pipe. The next size under is 50 mm. The front verandah is borderline for two downpipes but the side verandah would need three. Concealing the downpipe is clever provided you can do it and they remain accessible if requiring maintenance. Note that the above does not include the rainwater diverted from the house roof by the spreaders. It could present a problem to do this if using 65 mm downpipes to drain the verandah. Firstly, spreaders divert a concentrated flow from another roof area and this could not be drained by a single 65 mm downpipe that serviced the section of gutter that received the additional diversion. A solution would be to run a longer horizontal pipe off the upper level downpipe to distribute the water more evenly to several lower downpipes but this would also necessitate having restricted size drain holes to evenly distribute the water. This is not a good idea if the upper gutter collects debris as this could then cause the small holes to block but fitting gutter guard could solve this. A longer horizontal pipe could however be open at both ends. The lower section of gutter that collected this additional flow would then be fitted with additional downpipes between the gutter's high points and the downpipe fitted at the low point, their required number and position depending on the additional area of the upper roof and the length of gutter serving the upper roof. For the charged pipes plumbed to the tank, while the multiplier is used to allow for wind driven rain when calculating the downpipe and gutter sizes, it is not used when calculating the amount of rain harvested. The house, garage and verandah roof area is 660 sq m. The pipes minimum flow capacity to the tank is best calculated by the pipe size, the run length, friction loss and the minimum available head. Your tanks are very big, you need to firstly determine the available head from the lowest downpipe after allowing for rain heads/leaf diverters, the tanks base/slab height, delivery system (head loss) and other factors. For the 660 sq m house roof plan area, you should allow for a 'safety' capacity that exceeds a 1:20 ARI, preferably by a minimum of 50%. 660 x 2.5 x 1.5 = 2,475 litres per minute. You will need more flow capacity than provided by 3 X 100 mm pipes to drain to the tank. The shed's roof area of 300 sq m would give a literage of 1,125 litres per minute when factored as 50% greater than a 1:20 ARI. Depending on the minimum available head and the run length, 2 x 100 mm pipes could be enough if you wanted to compromise having a 'safety' margin. EDIT 26/11/2013: First time posters (and sometimes others) who are given detailed time consuming answers to involved questions without so much as a thank you in return should consider how their actions might impact on others seeking advice. My company received an almost identical query from someone within days of the above reply being given and against our better judgement, we replied gratis. Again, no thanks were returned. If the above answer has helped someone else, then it has still been worthwhile. 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: Rain water tanks & storm run off. 25Oct 14, 2012 3:34 pm Hey H2O,cheers for the pm,your advise is invalueable,cheers Block bought 1st RBC X! 2nd Ventrua,Keeper! Pstart 18/7/11 Ethwks jan 2012 Slab Bricks- finished 7/6 Roof Trusses 15/6-cbond 21/7 viewtopic.php?f=31&t=41185 Re: Rain water tanks & storm run off. 26Oct 14, 2012 4:01 pm I just read another thread about native gardens & lush gardens re water use. I have oftern wondered why rain tanks are not in all gardens,they should.Recylcling water as say grey water etc,it really should be a MUST have. Why there is not more insentive to install them when our water supply level is at times at a critical level. Why is this something alot of people do not think about or do, it saves water & costs,i also find some people that have bore water use it whenever they like without regard for how much they use. Just my green thought for the day Block bought 1st RBC X! 2nd Ventrua,Keeper! Pstart 18/7/11 Ethwks jan 2012 Slab Bricks- finished 7/6 Roof Trusses 15/6-cbond 21/7 viewtopic.php?f=31&t=41185 Re: Rain water tanks & storm run off. 27Dec 01, 2012 2:04 pm Hi Kat, I don't know if you have also read the thread that I have linked below but if not, then I suggest that you do. viewtopic.php?f=35&t=60317 The reason that I suggest that people feed their wet system pipes into large outlets fitted between 100 - 300 mm above the bottom of the tank (depending on the size of the tank) is to avoid the problems associated with wet system horizontal pipe(s) accumulating debris due to the flow velocity being insufficient to flush most of the debris up a vertical riser. Bacteria breaking down debris not flushed into the tank from the wet system pipes takes oxygen from the water and the water then becomes anaerobic because the pipe offers no air/water interface. If this water becomes stagnant, it can and often will pollute the clean water in the tank. A build up of debris can also restrict and even block the flow path. Water entering the tank from a low inlet also oxygenates the anaerobic zone and saves water by reducing and often eliminating the need to flush and dump rotting debris retained in the wet system. For many property owners, this can be thousands of litres of water every time the pipes are flushed. The Gympie installation discussed in the other thread is yet to be finished and summarised but that system needed the safe guard of having an additional flow path to assist the pipe's flow rates as the vertical risers may have a maximum 250 mm head after leaf diverters are fitted. What has evolved is a system that I will be recommending to everyone who has a wet system in place of my previous recommendation as it only needs smaller inlets fitted to the tank in addition to the vertical risers. To do the same for your single tank system, you... Have two 50 mm ball/gate valves fitted about 200 - 300 mm above the bottom of the tank and position them within 75 degrees either side of the outlet that supplies the pump. Fit a 100 mm DWV Tee to the end of each 100 mm DWV pipe near the tank and connect a vertical riser to each Tee's branch to divert water to the top of the tank. Fit a 100 mm DWV coupling to a short horizontal 100 mm DWV pipe exiting the Tee. Fit a 100 x 50 mm DWV level invert taper into the coupling. Fit a short 50 mm DWV pipe into the invert taper. You then... Screw a 50 mm poly barbed director to a 50 mm DWV female iron adaptor. (The fitting is not made of iron!) Fit a short length of suitable UV stabilised hose to the director and then fit a second director to the other end of the hose. I use pond hose. Screw the director into the 50 mm ball/gate valve. Fit the 50 mm female iron adaptor to the pipe. Make sure you do this last I haven't mentioned the use of teflon tape and solvent glue as I assume that an experienced person would be doing this for you. By making this simple adaption, the pipes will be regularly flushed of debris by the increased velocity through the smaller pipes and this will result in low maintenance, higher yield and better quality water. The water quality at the bottom of the tank is always the worst in the tank. If you draw water for outside use, it is best removed from a low fitted outlet. If you draw water to supply the house, the water should be drawn from a higher source. As your tank is also on a downslope, you should also have majority use of a first flush chamber if you decide to incorporate one with a sediment trap as it will be above the tank's water level most of the time. If you elect to do this and have trouble sourcing any parts, just PM me. 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: Rain water tanks & storm run off. 28Dec 01, 2012 3:56 pm Once again SH20 your a champ We may have come alittle unstuck re the water tank atm,have to now have the house painted instead of doing it ourselves so the spare $$$$ atm are going there. May do the tank before winter next year or when the now house is sold or rented do it then,we want to pay cash. Will keep you updated as to how we go & may ask more questions,cheers heaps kat Block bought 1st RBC X! 2nd Ventrua,Keeper! Pstart 18/7/11 Ethwks jan 2012 Slab Bricks- finished 7/6 Roof Trusses 15/6-cbond 21/7 viewtopic.php?f=31&t=41185 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 17287 Hello I am developing 2 side by side units. Wish someone can help me on the following questions 1) Which stage should be the storm water pipe installed during the new… 0 7777 If you need to be able to access these then you may need to dig them out and cut them so you can add a socket and a riser to the required height. We normally add a… 1 6822 |