Water Pressure & Water Flow
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MEASURE YOUR HOME'S WATER CAPACITY AND WORKING PRESSURE
Water pressure can vary from home to home, even on the same street. So it's important that you take a measurement at your own home. If you push your system beyond its capacity, the danger is that it can create water hammer and costly damage to your piping system. Also, if you exceed the pressure or water flow (GPM) you have available, your system will not function or work efficiently. The following are two reliable ways of determining your home's water capacity. We recommend using the flow and pressure gauge method because it's fast and easy.
DETERMINE THE DIAMETER OF THE WATER SUPPLY LINE
Call your local water company or measure your supply line (the pipe leading from the water meter to your house). - Locate
the outside faucet that is closest to your water supply
line (we'll call this Faucet 1).
- Locate
another faucet on your house and attach a pressure gauge
(we'll call this Faucet 2). Open Faucet 2 all the way
and record the static water pressure below.
- With
Faucet 1 open all the way, check the pressure reading
on the gauge at Faucet 2. If it is less than 40 PSI, turn
down the water flow from Faucet 1 until the reading reaches
40 PSI. If it is greater than 40 PSI, record the dynamic
pressure reading below and go to step 4.
- Place
a five-gallon bucket under Faucet 1 and time how long
it takes to fill it. Use the chart below to convert to
gallons per minute (GPM). This test tells you what your
home's water capacity is measured in GPM at 40 PSI.
- Repeat this procedure at 45 PSI and 50 PSI. Record these three results on the chart below.
This is how much water is available with a working pressure of 40 PSI or the higher reading that you recorded. (Minimum operating pressure for most sprinklers is 35 PSI.) If you use a different size bucket, time how long it takes to fill it. Convert this to gallons per minute using the following formula:
Time
to Fill Bucket |
Gallons
Per Minute |
15
Seconds |
20
GPM |
20
Seconds |
15
GPM |
25
Seconds |
12
GPM |
30
Seconds |
10
GPM |
40
Seconds |
7.5
GPM |
60 ÷ Seconds x Gallons
For example: A two-gallon bucket that fills in 15 seconds means the available flow is 8 gallons per minute.
60 ÷ 15 x 2 = 8 GPM (gallons per minute)
Note: In freezing areas, poly pipe should be used downstream of zone valves.
Use 5 to 6 wraps of "Plumbing" tape on threaded fittings. This will allow parts to be assembled hand tight and not leak. It also allows for heads to be rotated to adjust them.
- Poly
pipe should be used in areas where the ground freezes more
than a few inches deep. If you install PVC pipe in an area
where the ground freezes it may be broken by frost heaves
even if the system is dry. If you live in an area where it
gets below freezing you will want to have your system blown
out in the fall.
- Put
a tee in the supply pipe where it exits the house, before
the Pressure Vacuum Breaker (PVB) and screw a cap on the extra
leg. This will provide an easy place to attach an airline.
- Don't
blow out a system at more than 40 psi or for more than two
minutes.
- If
the system has rotors (heads that turn) the gear drives are
lubricated by the water and if run dry will be damaged.
- Multistream
rotors are the most sensitive to dirty water. City water is
typically fine. If you have dirty water the 570 series is
the most forgiving. To check your water, fill a clean, white,
five-gallon pail and look for sand or debris. If you see any
contamination do not use the multi stream head.
- Use
bigger pipe. The smaller the pipe, the faster the water flows.
The faster the water flows the more friction it has with the
pipe. More friction means you loose more pressure. Larger
pipe results in water flowing slower through the pipe and
less friction. Larger pipe results in less pressure lost due
to friction.
- Funny
pipe is typically run for 2-3 feet between the head and the
pipe. The closer you are to the valve, the farther you can
go. First head on the zone may be able to use 5-6 feet of
funny pipe with out a problem.
- Use
PVC tubing cutters, not a hack saw. Tubing cutters are like
a rose bush pruner with a ratcheting handle. They give an
extremely clean cut on 1"-1 1/4" PVC pipe. They
also work well on Funny Pipe. Sears sells a nice one (#51254).
- Build
the system on top of the ground. Glue it all together and
test it out. Make sure you get the coverage you want and make
any desired changes before you dig. Cut it into a few big
sections and then did your trenches. If you leave it on the
lawn for a few days your grass will yellow a little right
where you want to dig. Glue it back together as you drop it
into the trenches.
- Put
in more heads than you think you need. They are inexpensive
and easy to remove if you decide you don't want one.
- When
using in ground valves use a big valve box. This will make
installation easier and will help if you ever have to service
a valve. Don't limit your self to the standard valve boxes.
A wood box made with 2x8 lumber and a wood or plywood lid
works well. Rake wood chips or gravel over it to hide it.
Two foot by three foot is a nice size for four to six valves.
- Heads
should be place so each area of the lawn is watered by at
least two heads. This is called head-to-head coverage. This
means if the head has a radius of 15', the next head should
be no more than 15' away. A little closer is better to allow
for adjustments. You can reduce the throw distance by up to
25% on all of our heads.
- When
doing a flow test to determine the capacity of your water
supply, be aware of changes in the neighbor hood that are
planned. If you are the first house in a new development you
may find the pressure and flow drop in the coming years as
more homes are built. Call your local municipality to find
out what they plan the pressure and flow to be once development
is completed. Static pressure does not help design a system.
- What
you need to know is the gallons per minute at 35-40 psi. Either
use the Toro flow tester (#53351) or test with a pressure
gage and a bucket. Put the gage on one outside faucet and
open the faucet. Now go to another outside faucet and open
it till the gage reads a steady 35-40 psi with the water flowing.
Measure how many gallons per minute you are getting using
a five-gallon bucket. If you have 1/2" pipe going to
the faucet you will probably get an unrealistically low reading.
You may want to install your PVB and a 3/4" faucet on
it to get a more realistic reading. One-inch pipe is pretty
standard for plumbing in the PVB for up to 12 gallons per
minute.
- When opening the PVB, open the inlet valve as fast as you
can. This will result in the internal float sealing the vent.
Opening it slowly may result in the float not sealing the
vent and lots of water purging from the vent area around the
to of the PVB. Some water leakage is normal when opening the
valve but it normally stops in a few seconds.
- Water
big areas with single stream rotors, small or irregular areas
with 570 series. Use multi streams on slopes, windy areas,
and because you like the look.
- If using poly pipe (the black stuff in a coil) consider having an irrigation company install the pipe. They typically use a vibratory plow to pull the pipe through the yard and do a lot less damage to the lawn than a trencher. The price is typically not bad.
- When
installing funny pipe or the regular poly pipe it is easiest
if the pipe is warm. Leave it in the sun on the driveway or
have a bucket of hot water to put the ends in to make it easier
to attach fittings to it.
- Leave room for more valves. You may want to add irrigation
to a garden or a drip system and it's a lot easier to allow
for it now.
- Call
before you dig. You may think you know where buried utilities
are but it's not worth the risk of injury or cost of repair
if you're wrong.
- Bury
your pipes 8-10 inches deep. This should put them below the
sprinkler body and out of reach for lawn aeration.
- Buy
a couple spare heads. Sooner or later one will be damaged
and need to be replaced. Nice to have some spares on hand.
- When
replacing a head, follow these steps. Dig out a donut of sod
about 18 inches in diameter. Dig out the dirt around the head.
Remove the old head. Install the body only for the new head.
Keep the cap, spring, riser etc off to the side. Turn on the
zone for a few seconds to flush the system. Install all the
parts for the new head. Put the dirt back in the hole. Reinstall
the grass donut around the head. Pack it and your done.
- Leave
extra wire at you timer an in the valve box. This will make
servicing and/or replacing parts easier.
- When you run the wires from the timer to the valve box, run
a couple extra conductors. This will make it easier to expand
the system and will give you spare wires if anything goes
wrong.
- Put
your timer in a convenient place. Easy access and good light
make it easier to change the program. Just inside the garage
door or in a carport may be convenient.
- Take
some pictures when all your digging is complete and you are
putting the pipes in. They will help you locate the pipes
if you ever want to change something. Put the pictures in
a plastic bag by the timer.
- Over
80 psi static may result in valve problems. A plumbing supply
place in your area should be able to provide a pressure regulator
to bring the pressure down below 80psi.
- Run
the irrigation system early in the morning. This is when water
pressure is typically at its best. It is also best for the
lawn. If you water in the evening the blades of grass will
stay wet much longer and make it easier for fungus to grow.
Early morning also has the least wind. Wind can easily blow
a spray pattern several feet off target resulting in dry areas.
- If
you are planning to irrigate a sloped area you should take
special care in laying out each zone. Run your zones across
the slope so all the heads in a zone are at the same height.
This will prevent the zone from draining each time it shuts
off. If this is not possible you may be able to locate spring
loaded PVC check valves that can be installed in the lines
to prevent drainage from occurring. If you install a system
that drains each time it shuts off you will have a hissing
and spitting sound each time a zone comes on until the air
is purged.
- Another
problem may occur if your system has a PVB. Air in the system
may allow the pressure at the PVB to drop below the minimum
25-psi and result in water purging from the vent.
- Think
about installing valve boxes in more than one location. One
for the front yard, one for the back, and maybe one for each
side. This could make the plumbing much easier especially
if your system will have many zones.
- Don't
mix different types of sprinklers on the same zone or valve.
The watering times for rotors vs. fixed-spray heads are very
different. You will want to have control over how long each
type is watering.
- You
can include more than 1 pipe in a trench. Depending on local
codes, we suggest using 1 inch Schedule 40 PVC upstream of
the control valves. Use at least 3/4 inch Class 200 PVC or
3/4 inch Poly Pipe downstream.
- To dig a trench under a sidewalk or driveway, take a length of PVC pipe and attach a hose to one end. Use the power of the water along with the strength of the pipe to dig your way under the concrete
Next Page: Sprinkler Placement Planning
