Your Questions

I’ve heard of a “rain switch”, do they work and where can I get one if they are effective?

I don’t have a lot of time to fiddle with my irrigation system.  It seems to work ok, but I need to save money where I can on my utilities.  Is there something quick and easy I can do?

Every time the sprinklers come on water runs down the gutter at the bottom of the hill. Our neighbors said we should rip out the sprinklers and put in drip irrigation, do we have to do that?

I want to plant some spreading groundcovers on the slope behind my house, what is the best way to irrigate them?

We moved into a house with a Toro ECx timer. The book that comes with it is confusing… can you help me set it up?

I have an automatic irrigation system and the irrigation is coming on every day.  Is this right, how do I know how often to irrigate?

Our gardener “fixed” our irrigation system last week, and now there is a different kind of pop-up sprayer in the lawn.  Is this right; does this make a difference?

How do I know when I have the right amount of sprinklers?

John's Answers

Frank B. from Windsor, CA asks:

“We have moved into a home we are retiring too here in Windsor.   The house is fine but the landscape needs some work – especially the irrigation system – it doesn’t seem to cover everything.  I got a quote from a contractor, but he talked about what seemed like a lot of sprinklers and valves.  How do I know when I have the right amount of sprinklers?”

Irrigation Essential's Response:

Frank thanks for the chance to help out!  The answer to your question potentially has several layers to it, but we’ll start with your most specific question first, which is about the irrigation delivery system – the sprinklers. 

We’ll start with how a spray nozzle “works”, and how that leads to “how many” sprinklers.  We’ll cover the key issues in principle, because we lack some of your specifics – but we will get you pointed the right direction.
A sprinkler needs to cover a given area, at the correct operating pressure.  By covering a given area, that means it needs to spray water and hit the sprinkler heads that are nearest, typically on either side and opposing it.  The “lingo” is pretty descriptive; it is called “head to head” coverage.  So for example, sprinklers with a 12’ nozzle should be 12’ on center (or less—if in a windy location), but never at spacing beyond 12’.  See the article Pressure and Spacing, for more specifics.  The pressure and spacing issue is critical – getting this part of the system layout wrong will build in problems that will be hard to overcome!

Amount of Water Available

The total water available for your irrigation system is determined by the water meter size and supply pressure to your property.  Ask the contractor to share that information with you (also available from the water utility), and show you his or her calculations for gallons per minute (GPM) per irrigation zone.  He doesn’t need to produce a beautiful drawing or spreadsheet of water use calculation, but at minimum he or she should produce the water use per zone (irrigation circuit), and tie that to the manufacturer’s product cut sheet or catalog information.  Also, there should be a “cushion” built into the calculations.  Example: if the total water supply is 20 gallons per minute at 60 psi, make sure the largest system is no more than 16 gallons per minute (20% less than max capacity).   Once you count up the amount of heads of a specific nozzle size (determines GPM), you can do the math on justifying the number of heads. 

We are not quite done yet!  A couple more key ideas:

Insist on a sprinkler head installation detail that is adjustable -- this will save you many headaches!  If the proposal from your contractor does not have a “swing joint” detail to mount your irrigation heads, that is similar to what you can see in our Video/Tutorial section in PDF as PROS-04 2B.pdf (example from Hunter Industries), then perhaps they are not the “professional” you need! 

Contractor Reference

As a quick aside, in California refer to http://www.cslb.ca.gov, and http://www.clca.org for the status and listings of professional contractors.  Email us back, if you still have issues concerning your irrigation system!

Hydro zones

Group plants of the same water requirement on the same irrigation zone.  In other words, high water use plants are separated from low water use plants.  Carefully consider how much lawn area you need, and downsize that to as small an area as possible! You can definitely have a beautiful, inviting garden, without relying on lawn or other high water use plants!  Check with your local nursery and seek out native plants, and drought tolerant plants.   Chances are you’ll be delighted by some of the beautiful plants that are available, that don’t require a lot of water or maintenance!

One more point on hydro zones, sun exposure has a significant impact on “how many” zones as well.  Example:  a lawn area on the north side of the house that has shade trees, should be zoned separately from a lawn area on the south side of the house, even if you have the capacity to run them all at the same time.

Soil Biology and Horticultural Practices

Soil building will ensure a thriving garden, and aid in water retention and uptake!  We highly recommend that you utilize OMRI rated organic soil builders, and organic fertilizers.  Synthetic landscape chemicals create a build up of salts in the soil that are harmful to the many beneficial microorganisms that exist in a healthy soil.  There is plenty of science behind this, please see our “Stop Chemicals” article. 

Where To Buy

We strongly recommend that you purchase irrigation products from an irrigation supply store.  If your contractor is buying the entire product at the local big box hardware store, chances are they are not the “professional” you need.  In your area, go to Horizon Landscape & Irrigation, 238 Todd Road, Santa Rosa.  Their phone is 707.584.7272
 

Delivery Systems • Posted on 02/22/2009 •   Permalink

Many times, seemingly simple questions have answers that span several disciplines (design theory, installation practices, horticulture and soil science issues), and can become burdensome for someone to try to take in all at once.

To facilitate understanding, we group our information in three broad categories: 

System Management — Irrigation scheduling.  Hitting the “moving target” of plant water need as it changes throughout the growing season.

Delivery System — Spray heads, rotors, emitters, etc.  We try to explain the principles behind how they function, and make sense out of the many look-alike products on the market.

Soil Biology — Living soils and horticultural practices play a very significant role in how effective irrigation can be, and the viability of the landscape.  Think of growing roots, not plants!  Healthy roots will ensure a beautiful garden!