How to save water like a pro with a water harvesting system

Agrinet’s six tips for installing a rainwater harvesting system and pressure pump.

Harvesting rainwater to irrigate your garden or supplement your household water usage is one of the most cost-effective and sustainable decisions you can make. Rainwater is free and if you don’t use this resource, it simply flows away in the stormwater system and disappears.

If it rains just one millimetre on a 100m2 roof, you can potentially harvest 100 litres of water. So, a downpour of 10mm could yield 1 000 litres of water.

Saving this water in a tank for a sunny day or dryer months is surely the way to go. In order to effectively use your harvested rainwater to water your garden, you can install a pressure pump linked to an existing irrigation system to move this water, under pressure, to where it is required. You can supplement or even replace your current water supply, whether it is from a borehole or municipal water. 

Saving you and the environment. If you are considering installing a rainwater harvesting system, these are the questions you would want to be answered and the steps taken for a successful installation. 

WHAT ARE THE KEY COMPONENTS OF A RAINWATER HARVESTING SYSTEM WITH A PRESSURE PUMP?

• Rainwater is harvested from a roof or slanted structure, from where water flows into a gutter or gutter system

• In order to stop debris / catch debris before it enters your tank, you need a gutter filter, such as a Gutter Buddy

• Piping to channel the water to your water-holding facility, whether that is a tank or underground reservoir

• A pressure pump, piping and fixtures

• There should always be a non-return valve, one-way valve or check valve installed as part of the pressure pump system and these are usually included in the package. (Isolation valves)

• Optional but recommended: Flow Control Switch

• Protective Housing for your pump.

SELECTING A WATER TANK AND DECIDING ON THE IDEAL PLACEMENT FOR CAPTURING RAINWATER

Water tanks come in all shapes, colours and sizes. The most important element to consider when purchasing a tank when looking at rainwater harvesting is the size. This will be based on the water usage needs of your irrigation system or your household usage. There are many options when it comes to water tanks so do your homework to get the best deal. Keep in mind, the larger tanks will need a special delivery as they are larger than your average bakkie.

RAINWATER HARVESTING INSTALLATION WITH PASCALI PRESSURE PUMP

If your house already has gutters and downpipes, it is a relatively simple process of selecting the best location for a tank. Select a location where ideally the most rainwater usually flows from but also consider that the tank should not block the view out of an important window. 

A water tank should be placed on a perfectly level, smooth and sturdy surface, preferably a few centimetres off the ground. Many homeowners lay concrete slabs or create compacted platforms. Keep in mind that a 5 000 litre water tank full of water will weigh more than five tons.

The reason why the base of the water tank should be lifted a little is to have the outlet of the tank slightly higher than the inlet of your pressure pump. This will help to keep the pump primed, or full of water, and prevent it from running dry and possibly causing damage to the motor.

The location of your water tank should also have enough room to install your chosen pressure pump securely and protect it from the elements.

CONNECTING YOUR GUTTERS TO YOUR TANK 

It is not recommended to directly link your gutters to your water tank, as debris can fall into the water tank and affect your water quality and the performance of your pressure pump. The best practice is to reduce the amount of large and small debris as much as possible that could land up in your water tank before the water hits the tank. This can be achieved by installing specialised gutter and rainwater harvesting attachments like a Gutter Buddy and First Flush mechanism.

The Gutter Buddy is designed to be installed at the point where your gutter outlet meets the pipe leading to the tank and will help stop large debris like sticks, leaves and insects to flow with your rainwater to the tank.

The First Flush mechanism, with its anti-cavitation feature, helps to prevent smaller debris like dirt and dust to flow into your tank.

It is very important to select the correct size of First Flush for the size of your roof. The larger the First Flush, the less likely it is for debris to end up with your harvested rainwater.

BASICS OF INSTALLING THE PRESSURE PUMP AND PIPING

Correct installation of your pressure pump is extremely important, especially when it comes to ensuring the longevity and optimal performance of your unit. 

Site requirements for installing a pressure pump connected to a rainwater harvesting set-up:

• An electrical point must be in close proximity to the location to power the pressure pump

• The electricity supply should also be secure and weather-proof. The distance to the pump from an existing power supply will affect the length of cable you need to install, keep in mind this will have an influence on the installation cost 

• A pressure pump is supplied with mounting holes in the base so that it can be fixed to the floor. This ensures that the pump always stays upright and in the correct position. Any kind of vibration or the mere action of turning on and off can cause a loose-standing pump to wander out of position

• Ensure there is a mounting platform/space (ideally concrete) to which the pressure pump can be mounted/fixed, close to the tank

• The routing of the pipe coming from the tank into the inlet of the pump should be as straight as possible for at least five to 10 times the size of the diameter of the inlet. In the case of our installation, our pipe diameter was 32mm, so we needed at least 150 to 300mm of straight pipe

• Straight pipe from the tank to pressure pump inlet, with isolation valve in the open position

• To prevent any turbulence in the water from entering the pressure pump. Installing 90-degree elbows close to the pump’s inlet causes turbulence, which can result in air bubbles forming which can damage the pressure pump

• Best practice is to install an isolation valve with your inlet piping. This is to make pump maintenance easy, as the inlet can be closed off, and the pump can be disconnected without your tank running empty

• An important factor to consider on the inlet is the size diameter of the pipe. Also, keep in mind that water pressure and flow is affected by friction inside the pipes. The size and length of the pipe will affect the flow and pressure where you need the water. If your pipe is too small, the water from the tank is not going to be readily available

• On the outlet our recommendation is to install a flow control switch, which acts as the brain of your system. The switch tells the pressure pump when to switch on and when to switch off, or when valves are open, or valves are closed.

PASCALI FLOW CONTROL SWITCH

• The outlet pipe needs to connect to the mainline of the house or your irrigation system

• Another isolation valve needs to be installed close to the pressure pump on the outlet pipe. Again, this is to make maintenance easier.

ISOLATION VALVE ON THE OUTLET

To protect your Pascali unit from the elements, and to ensure the pressure pump works for longer, install the machine in a little housing unit, taking care that there is sufficient airflow around the engine.

WHICH PASCALI PRESSURE PUMP SHOULD I USE FOR MY RAINWATER HARVESTING SYSTEM?

All Pascali pressure pumps can be used for rainwater harvesting systems, but because of debris, the centrifugal and jet pump units are a better call. The size of the pump required depends on your water and pressure needs.

Specialists at Pascali will be able to advise you on exactly what will suit your requirements and will also refer qualified installers in your area. 

For more information on how to install a water tank and pressure pump, have a listen to one of Pascali’s technical advisors who share tons of information and tips on the Pascali website – Visit: pascali.co.za

For more information, Visit: www.agrinet.co.za