Working out your flow rate from your tap is critical in designing a successful watering system.
What is a “flow rate”? This is the amount of water, as expressed in litres per minute (LPM), available from your tap that you wish to use. Flow rates vary within your property, from house-to-house, street-to-street, suburb-to-suburb.
Unfortunately, most people, including tradesmen, guess what their flow rate is, or simply believe that it is ‘good’ or ‘ok’. However, guessing your flow rate leads to inaccuracies and potential loss of time and money if the wrong sprinklers are specified and there are not enough zones to run the system. This is why it is important to be accurate.
If you don’t have a water flow meter, you can use the bucket method to calculate the flow rate.
To work out your flow rate, you will need a tap with all the fittings and hoses removed, a bucket or large container with Litre markings, and a watch or timer.
The next step is to open your tap fully and then place your bucket under the tap and start timing how long it takes to fill. Do this step 3 times to work out your average time.
Now for the calculations. For example, if you have a 9L bucket and it takes you 15 seconds to fill, this works out to be 36litres per minute (LPM). An easy way to calculate this is to divide 60 seconds (1 minute) by the time it takes you to fill the bucket (15 seconds), 60÷15=4. Now, multiply your full bucket size (9L) by 4, (9×4=36). So as calculated, at your tap you have available 36LPM.
However, caution dictates to subtract 10% – 20% from this figure to allow for friction loss through pipes and fittings. So in this example, 30LPM is a safe calculation for your flow rate for your watering system. This figure can change depending on your irrigation pipe size.
Calculations and measurements in irrigation are so important because, just like everything else, it can cost you precious time and money if done incorrectly.
Vince is Managing Director of Hills Irrigation and is supported by Lisa in an administrative capacity. Andrew, Isaac and Megan look after the day to day needs of both online and shop customers. As Project Manager, Vince is also responsible for installation projects along with his team. It is his responsibility to work closely with clients to ensure that scope of work is understood and followed.
