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Water pressure and water flow issues for gardeners

May 03, 2012 -
   
  Water pressure and water flow issues for gardeners
Tricia uses inexpensive tools to check her water pressure and water flow.
 
   

Water pressure and water flow are key to answering that basic gardening question, How do you get water to the plants?

We all know how to water plants.You can:

*  hand water (time consuming)
*  move an oscillating sprinkler around (wastes water as it sprays through the air, and haven’t we all forgotten to turn off the sprinkler?)

Best of all though, for:
1)  steady supply of water to your plants
2)  water conservation
3)  convenience
is drip irrigation on a timer.

To plan a drip irrigation set-up you need to know your water pressure and water flow. In our new video Tricia shows how to get these numbers, with a few inexpensive tools. It’s not hard. Just follow the steps.

HOW TO MEASURE WATER PRESSURE


The first thing to figure out is how much water pressure you have. Then you can move on to looking at water flow.

It’s easy to check your water pressure. Turn off all appliances or hoses that would drain from that water source. Screw on a water pressure gauge, and turn on your faucet. The gauge will show your pressure in Pounds per Square Inch, commonly abbreviated as psi.

HOW TO MEASURE WATER FLOW

Have you seen those abbreviations GPM and GPH when you’re reading about irrigation?

In our video Tricia explains that those mean Gallons Per Minute and Gallons Per Hour.

WHAT ARE YOUR GALLONS PER MINUTE?

There’s an easy way to establish the GPM from your water source—all you need is a bucket and a stop watch. Watch the video to see how Tricia does it.


Five gallon buckets often hold more than 5 gallons, so Tricia pours 5 one-gallon jugs of water into the bucket.



Tricia marks the 5 gallon line in the bucket.



She puts the empty bucket under the spigot, gets out her stop watch, turns the spigot on full blast, and times how long it takes the water to reach the 5 gallon mark.

In a nifty piece of animation, our video shows the formula to apply.

5 (for the number of gallons) divided by the number of seconds to reach the 5 gallon mark = gallons per second. Multiply that number by 60 = gallons per minute.

Multiply again by 60 for gallons per hour.

To take full advantage of the capacity of 1/2” poly tubing you will need 200 gallons per hour.

MAKING CHOICES ABOUT YOUR IRRIGATION SYSTEM

Look at your water pressure (psi) and water flow (GPH) and what you need to water (see our Drip Irrigation video for your equipment choices).

Now you can put together the mix of:

pressure regulators
poly tubing with emitters
drip tape
soaker hoses
emitterlines

that are right for your water supply and landscape.

DO YOU NEED A PRESSURE REGULATOR?

If your pressure is over 30 psi, you need a pressure regulator to ensure your drip emitters don’t pop out, or emit more water than you want.

Drip emitters are rated in gallons per hour at a specific pressure. For example, mini-sprinklers can have a flow ranging from 4.4 to 30.5 gallons per hour depending on the pressure and the sprinkler model.

CHOOSING THE RIGHT PRESSURE REGULATOR

Poly tubing requires 25 to 30 psi to run well.

Drip tape, soaker hoses, and emitterlines need much lower pressure at 10 psi.

Choose your pressure regulator to produce the pressure you need for the type of system you are running—either drip tape and soaker hoses, or poly tubing with emitters.

For drip tape and soaker hoses, choose a pressure regulator that reduces pressure to 10 psi.

For poly tubing with emitters, choose a pressure regulator that reduces pressure to 22-25 psi.

Some of our pressure regulators are labeled for hi flow. Use them if your flow is over 8 GPM.

For more information about drip irrigation, we recommend the clear and useful book, Drip Irrigation for Every Landscape.

Measure your water pressure and water flow, and you’re on your way to planning your drip irrigation!


Categories: Drip Irrigation, Poly Tubing, Drip Emitters, Drip Irrigation Supplies, Garden Soaker Hose, T-Tape, Emitterline, Water Hook-Up, Landscaping & Flowers, DIY Garden Books, Organic Gardening 101


Cindy Says:
May 5th, 2012 at 10:32 am

Wow… this answers a few of the questions I had when I called your company just a few days ago!  Thanks for posting.  I still do not understand the “1” poly tube, “2” poly tube references in the video, however.  The diagrams in your catalog show a “header” poly tube with several poly tubes with emitters tee’d off of the main one.  So if you have 4 lines for a bed tee’d off a poly line running from the faucet, is that “1” poly line?  Or “4”?

Thanks.

Charlotte from Peaceful Valley Says:
May 8th, 2012 at 4:47 pm

Cindy, Thanks for asking! That counts as 1 poly line. The maximum length of your usable poly line depends on your pressure.

Robert Boone Says:
Mar 30th, 2013 at 6:20 pm

I thought the psi was limited by the type of emitter line.

Charlotte from Peaceful Valley Says:
Apr 3rd, 2013 at 11:56 am

Cindy and Robert, Here is more information from our drip expert:

There are a couple of different issues being discussed.  First of all, our 1/2” poly line has a maximum flow rate of about 240 GPH or 4 GPM.  If it is a long run, higher pressures (than 10-15 psi) might be needed to keep the pressure and flow up over the length of the run.  But that will still not increase the maximum flow that can go through the 1/2” poly.  Also, if you have emitters installed on the poly line, they could be the limiting factor. For instance, if you have 120 emitters that put out 2 GPH, you are at the maximum flow rate the 1/2” poly can handle. 

The same applies to drip tape if you are running it off of a 1/2” poly supply line.  Our drip tape puts puts out 40 GPH per 100 ft of tape, so 600 ft of drip tape is the limit on one 1/2” poly supply line.  More pressure will not increase the maximum flow rate for the poly.  The size of the tubing itself is the limiting factor. 

As for the psi being the limiting factor for emitter line, our 1/2” emitter line is pressure compensating over 15-60 psi, but it too has a flow rate that can be a limiting factor for the 1/2” poly supply line.  The emitter line has an emitter every 12 “, with a flow rate of 1GPH per emiter (per foot).  So 240 feet would be the max you couuld run off of the 1/2” feeder poly line.

Melanie Says:
May 24th, 2013 at 9:39 am

I am running 288 ft (8 runs of 35ft) of soaker hoses connected with 1/2” poly.  When I test the individual soaker hoses they drip well but when I connect them all and turn the faucet down so as not to blow the hoses (the poly pops ) the soaking is slow and spotty.  My flow rate is 10 gal/minute.  Do I need a pressure regulator and what is the determining factor - the soakers or the poly?

Charlotte from Peaceful Valley Says:
May 28th, 2013 at 4:50 pm

Melanie, For a pressure regulator, you will need a high flow (since you are over 8 gpm) that reduces to 10 psi since that is appropriate for soaker hose (IRH821).

In trying not to pop your poly connection, you may be having to turn the water down too low to adequately satisfy the soaker length you are running (which is well within soaker capacity).

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