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 100m 2 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 existingirrigation system to move this water, under pressure,to where it is required. You can supplement or evenreplace your current water supply, whether it is froma borehole or municipal water.

Saving you and the environment. If you areconsidering installing a rainwater harvesting system,these are the questions you would want answeredand 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 slantedstructure, from where water flows into a gutteror gutter system

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

• Piping to channel the water to your waterholding facility, whether that is a tank orunderground 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.

The base of a water tank should be lifted so that the tank is higher than the inlet of the pump.

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

Water tanks come in all shapes, colours and sizes. Themost important element to consider when purchasinga tank when looking at rainwater harvesting is thesize. This will be based on the water usage needsof your irrigation system or your household usage.There are many options when it comes to water tanksso do your homework to get the best deal. Keep inmind, the larger tanks will need a special delivery asthey 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 bestlocation for a tank. Select a location where ideallythe most rainwater usually flows from but alsoconsider that the tank should not block the view outof an important window.

A water tank should be placed on a perfectlylevel, smooth and sturdy surface, preferably a fewcentimetres off the ground. Many homeowners layconcrete slabs or create compacted platforms. Keepin mind that a 5 000 litre water tank full of water willweigh more than five tons.

The reason why the base of the water tankshould be lifted a little is to have the outlet of thetank slightly higher than the inlet of your pressurepump. This will help to keep the pump primed, orfull of water, and prevent it from running dry andpossibly causing damage to the motor.

The location of your water tank should also haveenough room to install your chosen pressure pumpsecurely and protected from the elements.

Connecting gutters to your tank

CONNECTING YOUR GUTTERS TO YOUR TANK

It is not recommended to directly link your guttersto your water tank, as debris can fall into thewater tank and affect your water quality and theperformance of your pressure pump. Best practiceis to reduce the amount of large and small debrisas much as possible that could land up in yourwater tank before the water hits the tank. This canbe achieved by installing specialised gutter andrainwater harvesting attachments like a GutterBuddy and First Flush mechanism.

The Gutter Buddy is designed to be installed atthe point where your gutter outlet meets the pipeleading to the tank and will help stop large debrislike sticks, leaves and insects to flow with yourrainwater to the tank.

The First Flush mechanism, with its anti-cavitationfeature, helps to prevent smaller debris like dirt anddust to flow into your tank.

It is very important to select the correct sizeFirst Flush for the size of your roof. The larger theFirst Flush, the less likely it is for debris to end upwith 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 thelongevity 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 at close proximity tothe location to power the pressure pump

• The electricity supply should also be secure andweather-proof. The distance to the pump froman existing power supply will affect the lengthof cable you need to install, keep in mind this willhave an influence on the installation cost

• A pressure pump is supplied with mounting holesin the base so that it can be fixed to the floor. Thisensures that the pump always stays upright andin the correct position. Any kind of vibration orthe mere action of turning on and off can cause aloose-standing pump to wander out of position

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

• The routing of the pipe coming from the tankinto the inlet of the pump should be as straightas possible for at least five to 10 times the sizeof the diameter of the inlet. In the case of ourinstallation, our pipe diameter was 32mm, so weneeded at least 150 to 300mm of straight pipe

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

• To prevent any turbulence in the water 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 main lineof the house or your irrigation system

• Another isolation valve needs to be installed closeto 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 forlonger, install the machine in a little housing unit,taking care that there is sufficient airflow aroundthe engine.

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

All Pascali pressure pumps can be used forrainwater harvesting systems, but because ofdebris, the centrifugal and jet pump units are abetter call. The size of the pump required dependson your water and pressure needs.

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

Correct installation of a pressure pump is extremely important.

Install a flow control switch, which acts as the brain of the system.

The routing of the pipe coming from the tank into the inlet of the pump should be as straight as possible.

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