They need to be made from stronger materials and structures and often require weighting or concrete reinforcement. Also, because underground tanks are positioned below ground level, you will need a pump to extract the water.
Above ground - The traditional round tank and some of the following space-efficient options are the most popular. Under the house - For houses on stumps or stilts a space saving option is to put the tank under the house or beneath decking. Against the wall - Another space saving option is tanks that go against walls or even act as garden walls. Some models can be joined together to make larger water storage tanks.
Tank material Rainwater tanks are manufactured in a number of different materials. Before purchasing a tank, you should make sure you have the right tank for the right job.
There should be at least two metres of plastic pipe between a steel tank and copper, brass or bronze fittings as they can cause corrosion. Galvanised and Zincalume steel can be considered as an alternative, however they are both prone to rusting.
Copper and stainless steel can also be considered for specific situations. Fibreglass - Fibreglass tanks are durable and resist corrosion however, they are often more expensive and can expose the stored water to sunlight. Stagnant water exposed to sunlight can allow algae to grow, some forms of which may be toxic for both humans and pets. Ensure you purchase a tank which is manufactured with sufficient pigment to prevent light entering the tank. There should be at least two metres of plastic pipe between a steel tank and copper, brass or bronze fittings as they can cause corrosion.
Galvanised and Zincalume steel can be considered as an alternative, however they are both prone to rusting. Copper and stainless steel can also be considered for specific situations. Fibreglass tanks are durable and resist corrosion. However, they are often more expensive and can expose the stored water to sunlight.
Stagnant water exposed to sunlight can allow algae to grow, some forms of which may be toxic for both humans and pets. Ensure you purchase a tank that is manufactured with sufficient pigment to prevent light entering the tank. These tanks are strong and heavy, which means they can be installed underground.
New concrete tanks may need to be flushed clean because they can release excess lime, leading to a high pH in the water. Some concrete tanks require a lining to be installed. Plastic tanks respond well to bumps and are non-corrosive.
These are often the cheapest tanks. Offering rain harvesting solutions from companies like RTS, Snyder, Graf, Bushman, Nino and more, you are sure to find the perfect product to meet your needs. Rain barrels come in a variety of colors, most commonly seen in green, white, black, and brown. Generally, they are opaque to minimize exposure to light in order to slow algae growth. They can be decorative or purely functional in style, and sizes usually range from 40 gallons to 80 gallons.
They are great for conserving water, energy, and money, since water will not need to be purchased for outdoor watering. Collected rainwater is perfect for a number of non-potable, water-intensive activities like watering plants or washing windows, pets, and vehicles. Made from a variety of materials, rain barrels can be used year round, and are commonly positioned under downspouts to collect water draining from the roof top. Many barrels come with screened lids to limit debris from entering.
The hose shutoff valve imbedded in most barrels allow the filling of watering cans or the connection of hoses for direct watering or to chain barrels together to increase capacity. Rain barrels make a sound financial investment as they provide access to free water after initial set-up costs. Consider, a 1, square foot house could collect over gallons of water for every 1 inch of rain. With level monitors, pumps, filters, diverters and more, The Tank Depot also offers a full range of accessories to transform your new rain barrel into a full rainwater collection system.
With a wide variety of sizes and styles to choose from, The Tank Depot is sure to have the right rain barrel for you. Tanks can also impart a slight taste to rainwater, at least when new. Concrete tanks can raise the pH of rainwater due to excess lime in the concrete, which may result in a bitter taste. Any taste your tank imparts to the water will usually abate after a while, but if you are going to use the water for drinking, dumping the first fill can flush out most manufacturing residues.
Also, using a good quality filter is recommended. Filtration levels in such systems can be tailored to your requirements, with simple particle filter cartridges ranging from 1 micron through to 20 microns or larger. You can also get carbon cartridges that absorb some chemical contaminants, or cartridges impregnated with silver to reduce bacterial growth. There are even refillable cartridges to fit these filter housings, allowing you to use any filter medium of your choice, or any combination of media in the one cartridge.
If you intend to drink the water, a silver-impregnated cartridge is the minimum you should use and, for full sterilisation, a UV ultraviolet steriliser can be fitted as the last stage of filtration.
UV sterilisation may be considered excessive by many country folk, but it may be mandated for drinking water— and your plumber may insist on installing this filter when installing your rainwater system. UV filters also need a source of electricity, of course. There are numerous speciality filters that can be used to remove specific contaminants such as heavy metals or organic compounds.
This is usually not a concern for rainwater, but if your tank is topped up from another water source such as a dam, stream or bore, this may be a requirement. Some poly tanks can leave the water with a plasticky taste—this comes from additives in the plastic leaching into the water and should definitely be filtered out if you intend to drink the water or use it for growing food.
This can usually be achieved with an active carbon filter silver-impregnated cartridges are usually active carbon-based , but if this is a strong concern, you may want to consider an alternative material such as stainless steel.
There is also pH correction, as rainwater is naturally acidic and so can corrode metallic fittings and pipes—in homes with rainwater tanks and copper pipes, blue staining is not an uncommon problem as the acidic water slowly dissolves the copper pipes over many years.
For this reason, plastic pipes are the preferred material when using rainwater or acidic bore water. Many newer homes are now plumbed with PEX polyethylene pipes, eliminating this problem, at least for pipework. Acidic water can also degrade brass fittings, of which most domestic tapwork is made, resulting in leaking taps due to corroded spindles and tap seats. The solution is to fit a pH neutralising filter, such as the whole house calcite water filters from Filter Systems Australia or Pacific Water Technology, which uses calcite calcium carbonate to neutralise the incoming water or, for more rapid neutralisation, dolomitic limestone, which has a considerable percentage of magnesium carbonate, may also be used.
All cartridge filters require replacement of their cartridge or filter media on a regular basis, while pH correction media slowly dissolves over time. Cartridge or media replacement can be required as little as once a year if your water quality is good, or more often if contaminant levels are higher. Obviously, the larger the filter cartridge, the longer between changes, so if this sounds like a hassle to you, then use the largest cartridges readily available.
These sorts of filter systems are readily available, including from some tank suppliers, hardware stores, or online stores such as The Tank Doctor www.
While most rainwater tanks come with a simple outlet near the bottom of the tank, the fact is that this is where the most polluted, anaerobic water is in the tank. The simple solution is a floating pickup, which consists of a float attached at the end of a flexible hose. The float keeps this water pickup near the top of the tank, so only the cleanest most aerated water is drawn off. If you just intend to use your rainwater on your garden, a pump may not be needed at all, especially if your tank is on a tank stand or your garden is on a slope and considerably below the tank level—gravity is the cheapest pumping system there is.
If you need more pressure than gravity can provide, you will need a pump. This will be the case if you intend to use the water inside the house in your fixed plumbing, or an irrigation system that requires normal mains pressure. Indeed, any application where you would normally use mains pressure will need the use of a pump. While there are a vast range of mains-powered pressure pumps available, rainwater pumps should be selected with three things in mind: application, reliability and noise.
For your application you need to know the pressures and flows you will require. Work backwards from the number of appliances you want to run at the same time. Add them up and this will give the required flow rate. The pressure required is determined by the pipe size used and the length of the pipe—the longer the pipe run, the greater the friction inside the pipe and the higher the pressure required to deliver a given flow rate, so select a pipe large enough to minimise frictional losses.
Reliability can be determined by several factors such as suitability to the application, construction materials, quality of the installation, water quality and pump and controller quality. However, if your pump is not in a critical application, such as just watering the lawn, then a lower cost pump may suffice. Most pumps are external to the tank—they have pipes running from the tank outlet to the pump inlet, and another pipe from the pump outlet to the point of use.
They can be fitted to a float to allow them to collect water near the top of the tank—this will greatly improve the water quality provided. Pressure pumps usually come with a pump controller often just a simple pressure-operated switch, but there are also many electronic models that turns the pump on and off as required.
Pumps broadly come in two flavours: single-speed pumps and variable-speed, constant pressure pumps. Most pumps are still single-speed units, with the pump being turned on and off by the controller as demand requires. This type of pump is almost always used in combination with a pressure tank, which provides a reservoir of water under pressure. This greatly reduces the number of pump starts and improves pump longevity.
But for more serious applications, such as supplying all water requirements to an off-grid home, you will need a pump capable of maintaining pressure when several taps are opened at once and a larger pressure tank to reduce the number of pump starts. Pressure tanks in the range of 60 to litres are typical in such applications.
However, tanks this large start to get expensive, and so the advantage over a variable-speed pump—lower price— is pretty much negated. Variable-speed pumps have controllers that can vary the pump motor speed to provide a consistent pressure regardless of the flow rate.
They eliminate the need for a pressure tank, but are considerably more expensive than single-speed pumps. While most domestic pumps are single-stage pumps the pump has a single impeller , multi-stage pumps, which have multiple impellers can deliver higher pressures. A pump professional not necessarily the local pump salesperson will be able to guide you in your selection once you have a clear idea of your application, flow and pressure requirements.
The quietest pump is a submersible one, as it resides inside the water tank. The advantage is near-silent operation, but maintenance can be more difficult as they need to be removed from the tank. A pump located outside should also be enclosed in a suitable pump cover to protect it from the weather and possible knocks and other damage. If you want to run your house primarily from rainwater, but still wish to use mains water as a backup, you can connect your home to both using a rainwater changeover system.
This can be as simple as a few manually-operated valves and a backflow-prevention valve in the mains line, or an automatic system can be used. The Davey Rainbank is a popular system which uses an electronic controller to do the water source switching. However, a similar result can be achieved with a simple hydraulic changeover unit such as the Acquasaver www.
One very handy device for your water tank is a water-level gauge. As with many such devices, simpler is usually better, but an electronic unit may have the option to record water level data so you can chart tank storage levels over time and get a better idea of available capacity during times of lower than normal rainfall, for example.
Energy use of pumps will vary depending on efficiency. The more efficient a pump, the less energy it will use to move a given volume of water. This water is pumped great distances and is delivered to homes at a much higher pressure than generally needed. Because of these factors, the embodied energy in mains water is quite high, relatively speaking.
Using a small pump to move water out of a rainwater tank will generally use far less energy than drawing that same volume of water from the mains. To get an idea of how little energy is needed to push water around, have a look at the pumping calculator at www. Using the average electric motor to drive the pump would result in an energy consumption of under watt-hours. For homes with off-grid energy systems, it can make sense to use a timer to water gardens during times of solar excess—the middle of the day.
However, if doing so, watering should be sub-surface and the gardens should be well mulched to prevent evaporative losses. A water tank can be a considerable expense, even after a rebate, so you want it to last as long as possible. The expected lifetime of any tank should be at least 20 years, and indeed, many tanks come with a 20 or even 25 year warranty.
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