Browse Forums General Discussion 1 Oct 10, 2021 7:34 pm Hi, We have recently bought a property on a quite steep slope. We have two tanks, one "upper" tank next to the house which harvests water directly off the roof, and another "lower" tank situated further down the slope which harvests water from the overflow of the upper tank. The overflow from the lower tank runs directly in to the street drainage. The pipe leading from the upper tank to the lower tank also has a water diverter which allows water to bypass the lower tank and run directly into the street drainage line (see image 1 and 2). When the diverter (which I'm pretty sure is a Blue Mountain diverter available from Bunnings) is set to flow in to the lower tank, it leaks significantly under pressure and does not allow any water to actually flow up the pipe and in to the lower tank. Several reviews of the diverter on the Bunnings website tell of an identical situation to mine. When we moved in the diverter was set to bypass the tank, and potentially has always been set this way, given that the upper tank is currently full to the brim and the lower tank is basically empty. I am considering removing the diverter and replacing it with a straight pipe running in to the lower tank. This would mean that all overflow from the upper tank would flow to the lower tank, and only overflow from the lower tank would flow on to the drain (see image 3). I have no experience with plumbing so have been learning myself by mapping out our current setup and experimenting with the various pumps and lines which are also part of this system. Is what I am proposing a reasonable solution or are there other factors to consider that I am not aware of ? Thanks! Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Re: Rainwater harvesting tank overflow 2Oct 10, 2021 8:55 pm What is the head?. Are the pipes 100mm (110 mm OD)? The Bunnings link shows a 90mm stormwater valve. Not sure if 100mm ones are made. Are both overflow outlets meshed? 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 harvesting tank overflow 3Oct 11, 2021 6:07 pm The head at the lower tank, shown in my first photo is approximately 2.5m. Not sure if this is relevant but the inlet to the lower tank is approximately 4m lower than the overflow outlet of the upper tank, due to the slope of our property. All pipes being used are 90mm. From what I can tell neither tank has meshed overflow outlets. Keen to hear your thoughts and any explanations would be greatly appreciated - as I said I'm learning from square one. Cheers Re: Rainwater harvesting tank overflow 4Oct 14, 2021 6:49 pm smiatke Not sure if this is relevant but the inlet to the lower tank is approximately 4m lower than the overflow outlet of the upper tank, due to the slope of our property. From what I can tell neither tank has meshed overflow outlets. That is the measure I was interested in, no reason then apart from the diverter for the lower tank not filling. The 90mm diverter isn't designed to work on a charged pipe but the water must really gush out if the lower tank doesn't fill. While there are no regulations prohibiting the use of the thin 90mm stormwater pipe on a charged system, it is not a good idea. This pipe should also be protected if exposed to UV as they go brittle in time. The outlets should be meshed to prevent rats/frogs/mozzies etc accessing the tank. The mesh is often removed because they can clog but they also present a flow restriction that reduces the overflow's discharge capacity. The flow passage through a 90 mm meshed outlet is usually about 84mm (the 90mm pipe is itself measured as an outside diameter anyway) and I always recommend replacing the mesh with a dual meshed air gap made by Rainharvesting. This provides the meshed protection while allowing the overflow to operate at full,capacity. https://rainharvesting.com.au/products/ ... ap-family/ Given that the lower tank would handle the overflow requirement from the inflow from the upper tank, your solution is the most logical but I would keep an eye on the overflow capacities of both tanks when you get significantly heavy rain as I am suspicious as to why the overflow mesh has been removed. 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 harvesting tank overflow 5Oct 14, 2021 8:02 pm Thanks for the info - really useful. Yes the water was gushing out of the diverter. It is possibly also damaged from previous use. Interesting about the meshed outlets. Not sure how long they've been removed for or if they were ever in place. Will definitely look at the air gap fittings. Why isn't 90mm recommended for charged/wet systems? Is this just due to the pressure built up from the water? The internal walls of the lower tank are a bit grimey, I guess from having a low water level for a long time. Any suggestions for cleaning them and is this necessary? I was thinking of using a Karcher pressure washer to spray down the walls. Thanks again. Re: Rainwater harvesting tank overflow 6Oct 14, 2021 8:29 pm I consider the air gap to be Rainharvesting's best product. 90mm stormwater pipe is flimsy, the walls are only 1.9mm thick. DWV (Drain Waste Vent) pipe is much stronger but also not pressure rated although it is more than suitable for charged systems. It is also UV stabilised. I wouldn't expect there to be much crud in the lower tank given that it only accepts overflow from the top tank but tank water invariably has a thin layer of organic material floating on the surface after it rains. This drops down to the bottom after 3-4 days but if it rains soon after and the tank is full, it is this organic film that builds up on the mesh. I assume that it is this fine organic film that has coated the wall but apart from that, you shouldn't have any sediment worth considering in the lower tank. How will you use the water in the lower tank? Is there a pump? It looks like you have also checked the lower tank's top meshed inlet to see if it is clean. Wise move. A good trick is to cut out an oversized piece of shade cloth and lay it over the mesh with the outside edge tucked up. When you check to see if the mesh is clean, just remove and shake the shade cloth. It looks like you have a bit of land there. Why not create some swales and drain any overflow to those, thereby recharging the ground water. Do you have any trees that could also use an extra drink? If you want to clean the tank, a pressure wash is the go but does the tank have a low drain valve? 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 harvesting tank overflow 7Oct 15, 2021 3:50 pm From what I can see both tanks only have outlets which are about 30cm from the base of the tank. Is this different to a low drain valve? Currently both tanks are set up pretty much just for garden watering purposes. Which seems a bit overkill considering the size of the tanks. There is a pump connected to the upper tank which pumps water to 2 taps in the back yard and sprinklers on the roof. There is a pump connected to the lower tank which pumps water to 2 taps in the front of the property, and can also pump water back up to the upper tank by turning a valve in the line. Haven't really thought about the swales idea, but given the capacity of the tanks I have been wondering about using them to supply water to the toilet and possibly the washing machine. Haven't really investigated what is involved in making the conversion though.... Thanks again for your input so far. Re: Rainwater harvesting tank overflow 8Oct 20, 2021 11:52 am smiatke From what I can see both tanks only have outlets which are about 30cm from the base of the tank. Is this different to a low drain valve? A dedicated drain valve (that most homeowners have their pump connected to!) is at the very bottom of the tank. 300mm is a good height to have an outlet valve if the water is also for potable use. Water tanks traditionally have water diverted to a large meshed inlet at the top of the tank and draw water from a valve at the bottom of the tank, the opposite to best practice!!! DIVERTED TO TOP INLET Water falling from a height can cause sediment resuspension. The top inlet is frequently located overhead of the tank's outlet that the pump draws water from. Not good! Charged systems ramain full of water to the vertical riser's level at the top elbow's invert. Charged systems operate with the same head regardless of how much water is in the tank. WATER DRAWN FROM A LOW DRAIN VALVE Water settles in stratified layers and the worst quality low oxygen water is the higher density higher acidic water that naturally settles at the bottom of the tank. This lower layer is referred to as the anaerobic zone. smiatke Currently both tanks are set up pretty much just for garden watering purposes. Which seems a bit overkill considering the size of the tanks. Agree. Bang for bucks means having year round use. smiatke .....given the capacity of the tanks I have been wondering about using them to supply water to the toilet and possibly the washing machine. Haven't really investigated what is involved in making the conversion though.... In the "old" days, it made sense to divert to a toilet to reduce the household use of mains water because back then, cisterns were usually 12/13 litre single flush units. These days, the dual flush smaller capacity cisterns have reduced water use by about 65%. Compounding this is the cost of plumbing to a toilet which most plumbers will tell you requires an automatic mains water switching device and fitting a check valve to the house mains water plumbing. Unless your council is one of the ones who have overruled the plumbing standards (mostly after listening to advice from vested interests or the unknowing) and stipulated that only an automatic mains water switching device can be used, you are allowed to fit a much cheaper and bullet proof manual mains water switching system. The cheapest and best (IMO) manual mains water switching system is one where you fit a second cistern valve snd plumb a PEX pipe from the pump directly to the second valve. This will also give you two isolation valves on the wall...these are your manual change over devices. One on...one off. The air gap at the top of both valves also prevents cross contamination of the mains water. This method saves more than $1,000 when compared to fitting an automatic mains water switching device and plumbing into the house mains water line. The best cistern valve to use is the Fluidmaster 400UK063. This valve is very compact and well designed as the float travels up and down the shaft. It costs about $20 in the big green shed. The coup de grace is the availability of two optional lower pressure seals with the (red) 242LP071 very low pressure gravity feed seal allowing the cistern to refill with a claimed 1 metre head positive to the seal. This is the manufacturer's claim but I have found that 750mm head is still enough to close the seal when the cistern is full. I turn my pump off for about 7-8 months of the year but it is still best to use it every week or two. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ The best year round high utilisation use of harvested rainwater is to supply the HWS. A floating intake filter draws the best quality water in the tank from 200 to 300mm below the water surface and if you also run it through a 10 micron cartridge filter, you will have good quality water supplied to the HWS that also sterilises. I am prototyping a floating intake filter right now and it will be superior to all others on the market as it will have the (intended) choice of either 200 or 400 micron filtration plus a couple of other tricks AND a lower price but it won't be available for several months at this stage. The Homeone thread linked below shows how a Homeone member designed his floating intake filter at low cost. viewtopic.php?f=35&t=97686 Supplying good quality rainwater to the laundry is also good utilisation if you wash with cold water. Rather than plumb to a mains water pipe, it is usually easy enough to drill through the wall and plumb a marked rainwater tap on the other side. I won't be available to post again on the forum until late Saturday at the earliest. I hope that this post has been of some help. 3in1 Supadiverta. Rainwater Harvesting Best Practice using syphonic drainage. Cleaner Neater Smarter Cheaper Supa Gutter Pumper. A low cost syphonic eaves gutter overflow solution. There is a whole lot more to know than just the answers you seek but they are a good start. Overflow outlets have a mosquito proof mesh. These… 3 8423 18 90484 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 31281 |