Archive for October, 2012

Often when I’m out at the local hardware I see people fossicking around for a replacement lawn sprinkler.  I am sorely tempted to tell them that they shouldn’t just buy any old sprinkler, there is a reason that irrigation systems are designed and having water applied evenly over a lawn is one of them.  The performance of sprinklers and pop-ups varies greatly.  Even at one given pressure, different brands have widely varying specifications in terms of how much water they put out over a given time period (ie how many mm of precipitation) and over what area (usually circular but not always).  I see specs from around 9 mm an hour right up to 60 mm an hour.  This translates to a six-fold difference in watering time!

Superimpose on that, the pressure your system is operating at and the output can vary from the stated specs quite widely.  Even scheme water with mains pressure, can vary.  With bore or dam water you really need to do some serious measuring to determine your flow rates.  Lastly, how many sprinklers you’ve put on a station will also affect the pressure they run at and therefore their output.  You just can’t add sprinklers to a station and expect that not to affect the output of each sprinkler.  Add another row and you may end up with dead patches because the sprinkler patterns no longer overlap (they are usually designed to overlap by 50%).

Another variable to think about when you water is wind.  The howling easterlies in the morning can have quite an impact on whether you end up watering your lawn or your neighbours!  Or the street.  Maybe water earlier, or after the winds have died down.

And lastly, please get out and watch your sprinklers working once in a while.  If they have filters, these can get blocked and that will affect the output.  Some nozzles have a habit of turning themselves around, occasionally helped by playful dogs, so when you think you are watering your lawn you may be watering something else – like the verandah!  Lawnmowers and dogs are both good at wrecking sprinkler heads.  So often when I’m out running early in the morning I am greeted by gushing sprinklers – and these may last for weeks on end.  I feel like popping a note in the letterbox but of course am never carrying anything on me!

Lastly, I was shocked to find out most people never touch their controllers to alter the settings from day to day or season to season!  OK, maybe I’m unique :-), I accept that but I certainly alter mine almost on a daily basis depending on the temperature and whether or not its rained.  If you have 4mm or more of rain in a day you probably don’t need to water unless we’re talking veges or other plants that are growing rapidly.  Four mm is commonly regarded as the minimum effective rainfall – so anything less that that you may as well ignore.

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