Browse Forums Eco Living Re: Rainwater collection advice 6Mar 16, 2016 2:03 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: Rainwater collection advice 7Mar 28, 2016 1:06 pm GUILLOTE Im from argentina... My roof is 200 sq meters. It will be one downpipe (60 sq meters of roof), 8 meters away from the tank, and another one (only one, in a corner of 200 sq meters of roof) 18 meters away from the tank.. The horizontal pipe is 20 meter long. Here arent heavy rains often, I think the 50mm pipe will be ok.. Our IFD (also called an Average Recrrence Interval) is based on a rainfall intensity over a 5 minute duration. Your rainfall pattern appears to be regular apart from July, August and September when it can be dry whereas October to April inclusive is quite wet. The average number of rain days annually are quite low, the average number of rain days per month being no higher than 10 in any given month but your annual average rainfall of about 1,000mm is reasonably high. I have also noticed that you regularly suffer bad droughts and floods, not unlike Australia. The rainfall pattern suggests to me that you do experience heavy rainfall at times and your roof drainage system needs to cope with this. Do the other houses where you live normally have roof gutters and downpipes or does water just fall to the ground? Also, if the houses do normally have gutters and downpipes, where do the downpipes drain to? Do you have a mains drainage system that also serves the other houses? Even in an area of very low intensity rainfall, a 50mm downpipe would not possibly cope with a 60 sq m roof area. Have a play with the flow rate calculator that I have linked below. You will need to change the roughness coefficient to 150 for PVC pipe but you will also need to allow for the friction losses imposed by elbows and tees and those friction losses are expressed as additional pipe lengths. Because the friction losses vary for the different pipe sizes, there are different figures applicable but you can do a Google search. Just be aware that a low restriction inlet will improve the figures provided by the calculator. http://www.calctool.org/CALC/eng/civil/hazen-williams_g Of interest, a 100mm pipe (actual internal diameter...NOT nominal size) with an equivalent friction loss length of 35 metres will flow at 450 litres per minute with a 300mm head. Also don't forget to size your tank's overflow so that its capacity exceeds the inflow capacity during a storm...you have a small tank that will quickly fill during prolonged rain. If you look up Torricelli's theorem or Torricelli's law, you will find a simple formula for determining how fast the overflow will discharge based on the outlet's diameter and the depth of mitigation the tank provides between the pipe's invert and the point where the tank will over-top. Just note that it presumes an open hole, i.e., one that is not meshed. At a guess as to your 1:20 ARI, I would say that you will need a distance of about 200mm minimum above a 100mm overflow pipe's invert. Because a side outlet is not as efficient in comparison to an internal standing pipe, you should also look at having an internal overflow pipe extension inside the tank with a bell opening as this is much more efficient and it will allow you to raise the height of the outlet's orifice so that you don't sacrifice as much storage capacity. Another way to dramatically increase the overflow efficiency is to plumb two overflow pipes into the one standing pipe...a vertical overflow pipe is mostly full of air and there is plenty of capacity to fit a second pipe. Having a single downpipe at the end of a gutter is bad design because it will compromise the gutter slope plus the gutters will carry a lot of weight during a high intensity rain event...water weighs 1 kg per litre. The best position for a downpipe is 1/2 way along the gutter because the gutter either side of the downpipe will have better slope plus the shorter run allows the water to drain faster. Contrary to popular belief, water does not flow as a uniform mass, it flows in streamlines and the water on the boundary layers (the bottom and walls) is stationary (the same as air on an aircraft's wing) unless there is turbulent flow. What this means is that the different layers are sliding over each other and this creates friction, the longer the gutter is, the more friction there will be. People generally understand about friction losses in pipes but not so when it comes to gutters. The gutters also need to slope (I suggest a minimum of 1:350). The smaller roof area will need a well positioned 100mm downpipe and a suitably sized gutter to match. Given that the gutters are straight, the larger roof area could get away with having two 100mm downpipes at 1/4 and 3/4 gutter length, this will give equal roof drainage to both sides of the two downpipes and a good gutter slope. Two 100mm downpipes would easily cope with the larger catchment area because good design will always exceed compliance even when the good design is not compliant but you still need to check as to whether you are bound by any roof drainage compliance and inspection certification where you live. I would be surprised if your building standards do not mandate minimum gutter cross sectional areas and downpipe sizes. We also use what we call DWV (Drain Waste Vent) pipe for charged wet systems because it is stronger and there is a larger variety of fittings. This pipe is universal and I would be very surprised if you didn't also have it in your country. If you want to have much cleaner water enter the tank (less sediment buildup), you should also look at installing a DIY sediment trap in a non turbulent section of wet system pipe. This is necessary to allow the carried suspended sediment to settle as bed load and fall down the trap. See the diagram below, note that DWV pipe is used. GUILLOTE I already put the horizontal pipe. It is a 50 mm polietilene. The deep point is it the otherside of the tank, with a valve to flush it. Near the tank, o will up the 50mm pipe to charge the tank from the top, but with a valve to charge from the bottom. Is it the "low restriction inlet"? It will help to flush and clean with pressure the wet pipe. If you have a sediment trap, it can also serve to flush the wet system but wet systems only need flushing to drain anaerobic water and crud...if you have leaf diverters and a sediment trap, your system will be clean. If you do fit a sediment trap, try to drain it during a dry period and leave the outlet valve at the end of the drain pipe open to air the pipe...but cover the opening with some shade cloth or similar to block pests from entering. Letting it air will allow the crud on the walls to dry out and when it next rains, a lot of that crud will be flushed through the open sediment trap...just be there to close it after it flushes. A low restriction inlet should only be fitted if you use leaf diverters. Here in Australia, it is mandated that water stored in a tank must first pass through mosquito proof mesh (less than 1,000 micron). A supplementary low restriction inlet really is a necessity for wet systems as it provides many advantages but it is not yet widely used because it is still a largely unknown method that was developed through the use of one of my products and the method later adapted to standard wet systems. I want to publicise the method here in Australia because it will collectively save Australian property owners who are not on the mains water grid billions of litres annually if it becomes widely used. As is, I actually get more international inquiries than Australian and it has now been used in many different countries. The advantages include... Boosts the available flow rate. Has priority use because it operates with greater head pressure than a vertical riser. Oxygenates the anaerobic zone. Allows the wet system to flush during every rain event. GUILLOTE Gutter height: 3.00m Leave eater: 2.60m Tank height: 1.8 to 2.0 m Head: 60 cm maybe (but i think, if i make the downpipe bigger (110 or 160mm), there would be more litres, so more pressure. im wrong? Wrong! Pressure is generated by the height of a column of water, not the volume or weight of the water in the column. One metre of water = 9.82 kPa. GUILLOTE The sifon in the inlet of the tank, help the velocity in the pipe? If you are referring to the low restriction inlet, then yes, it will act as a syphon with a greater hydraulic head than the vertical riser because the variable water level in the tank will always be lower than the water level at the top of the vertical riser above the tank. This in turn increases the wet system's drainage capacity and hence the velocity. GUILLOTE Is it posible to only have a low inlet to the tank? Large inlets are expensive and it is often not possible to fit them to smaller tanks. We usually use a 40mm inlet. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. 18 90372 DIY, Home Maintenance & Repair But if it is a ground level open pit, then it is not a charged system. No surprises there. The pipes have obviously been altered and there would be a reason for this.… 3 31235 Once you know the basics, the rest is easy. Read my post in the thread linked below. viewtopic.php?p=1919271#p1919271 2 19473 |