Watering with a Firehose: Rotor Heads

Rotors are a great way to water large areas.  Rotors are significantly enough more efficient than spray heads that they should be considered whenever possible. 

Care should be taken with rotor heads to make sure that you put the proper nozzle in each head so that they are all matched precipitation rates (see the explanation of matched precipitation rates in the spray head post).  This takes a little bit of thinking when designing your system for your flower beds or Outdoor Living Spaces

I will not get into this in too much detail but there are two ways to handle matching the precipitation rates.

The first way to match the precipitation rates is to find the inches per hour for a nozzle and then install the smallest rate in the quarter sprays, approximately two times the quarter rate in the half sprays, and about four times the quarter rate in the full sprays.  This will ensure that the water will be applied evenly. 

The thing to keep in mind with this method is that the nozzle that you will put in the full head will spray a lot farther and potentially result in a lot of watering concrete, but the efficiency is worth the trade off to me.  Design around the shortest distance and deal with the overspray.

The second way to handle matching precipitation rates begins with the design phase.  Break up the system so that the quarters and halves are on a valve together and the fulls are on a valve together.  You then proceed as mentioned earlier with nozzling the quarters and halves, but the fulls will get either the same nozzle as the quarters or the same nozzle as the halves. 

You manage the difference on the clock with the watering duration.  If you use the same nozzle as the quarters, you will set that station for four times the run time of the quarters and halves.  If you use the same nozzle on the halves and fulls, you set the run time on the full heads for twice that of the other.  This is a tricky little way of controlling the efficiency and being able to prevent a lot of overspray.  See the Watering Your Landscape in Utah posts for setting your clock.

As far as the disadvantages of these heads, they do have working gears inside them so there is the increased potential of those parts breaking–at least more so than for spray heads. 

Also, there are rotor heads that will cover areas down to as small as about fifteen feet, but any smaller and you have to use the spray heads.

Last, these heads operate most efficiently at about 55-60 p.s.i., so they are right out when it comes to low pressure systems without the aid of a pump.  Operating at a pressure that is too low will result in cute little green rings around the heads.

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