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| Filter checkup at Igingilanyi Village drip system- Iringa |
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| Illustration of a very simple drip system |
Hellow, welcome to Water Droplet Community. To day I would like to present to you basic parts of Drip irrigation system with their general management. Simple language have been used to equip easy understanding . You are welcome.
Valves:
Valves turn on or off the water flow through a
pipe.
Isolation valves are manually operated valves
used for infrequent shut-off of the water. Typically an isolation valve is
located at the water source so the water can be shut off for repairs or shut
off during the non-irrigation season. Isolation valves may also be installed
anywhere on the irrigation system to allow the shut down of sections for
repair, this is common on large systems where shutting down the whole system
for a repair would be inconvenient.
Control
valves are
the valves that turn on and off the water to individual “circuits” or areas of
the yard that are irrigated separate from one another. The control valves can
be automatic (usually electric-powered using a solenoid) or manually operated
(hand-powered, ie; turn, turn, turn!) There may be just one control valve or
there may be several control valves on a drip irrigation system. For example
one control valve may turn on and off the water to emitters/drippers in a
vegetable garden. Another control valve might turn on and off the water to
emitters for some hanging pots on a patio. Another control valve might turn on
and off the water for the emitters at shrubs around the house. Another could
even turn on and off water for sprinklers in the lawn, or water for filling the
swimming pool or pond. For more information on valves for drip systems, click here
Backflow
Preventer:
The
backflow preventer is a device that prevents dirt, salmonella, dog pee, etc.
from being sucked back into your drinking water from the drip system. You need
to use a backflow preventer on ALL drip systems. No exceptions! For more
information on backflow preventers, why you need one, and a simple guide to
which type to use, see the page on backflow preventers- click here
Pressure
Regulators and Pressure Reducing Valves:
A pressure regulator reduces the water
pressure and keeps it at a constant level. A pressure reducing valve is another
name sometimes used for a pressure regulator, both are the same thing.Most drip systems operate best at lower water
pressures than are common in a typical water supply system. A pressure
regulator is used to lower the pressure and then keep it at that pressure, even
if the incoming water pressure varies up and down. You probably will need to
install a pressure regulator on your drip system if your water pressure is
higher than 2,8 bars (40 PSI). Keep in mind that a pressure regulator only
reduces the water pressure. It will never increase the water pressure, so if
you don’t have enough water pressure a pressure regulator will cause you to
have even less!
While the name sounds similar, a
“back-pressure valve” is not a pressure regulator and has a different purpose.There are two general types of pressure
regulators used, non-adjustable ones (with a factory pre-set outlet pressure)
and ones with user adjustable pressure settings. Either type may be used for a
drip system. As a general rule the non-adjustable type are used for small
homeowner drip systems that utilize less than 3 control valves.
Those people
who want the best of everything, regardless of cost, would want to use the
adjustable-type pressure regulators, as they allow more flexibility and are
usually more accurate.Inexpensive, non-adjustable-type
pressure regulators (see photo below) are most often used for simple
home drip systems. They are typically made of plastic and have a pre-set outlet
pressure. They often have very specific flow ranges and will not work if used
at flows higher or lower than the listed range. Since they are not adjustable,
be sure to buy the correct one for the flow and pressure your drip system
needs.
The non-adjustable-type regulators must be installed AFTER the control
valve, so if you have more than one control valve you will also need one
regulator for each of the control valves. If a valve is installed after a
non-adjustable-type pressure regulator it can result in a pressure surge that
can damage your drip system. It has been my experience that when used on
systems where very high water pressures are present some of the
non-adjustable-type regulators may allow a quick pressure surge to pass through
just after the valve is opened. If you experience problems with drip tubing
blowing out of the fittings right after the control valve is opened you may be
experiencing this problem. Try switching to an adjustable-type pressure
regulator.
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| Add cNon-adjustable-type pressure regulator.
(Install after control valve.)
Notice this regulator has pipe threads. See the section below on pipe vs. hose threads.aption |
The
classic adjustable-type pressure regulator can go before or
after the control valve. This type of regulator is most often made of brass or
bronze, (some plastic versions are made) and has a large screw on it that is
used to adjust the outlet pressure. The adjustable-type pressureregulator you use needs to be the correct size
as rated by the manufacturer for the flow range. Unfortunately the sizing
formulas they provide are somewhat difficult to understand. As a general rule a
50mm (3/4″) adjustable-type pressure regulator will work acceptably for drip
systems designed using the Drip Irrigation Guidelines on this website, provided
the regulator is set to reduce the pressure by at least 1,4 bars (15 PSI). It
is common for the pressure regulator to be a smaller size than the pipe it is
installed on. Adjustable-type pressure regulators are often found in the
plumbing department of hardware stores rather than with the irrigation
supplies.The adjustable-type pressure regulators may be
installed either before or after the control valves, whichever you prefer. On
larger drip systems, with multiple control valves, the valves are often grouped
together in one or more locations and a single adjustable-type pressure
regulator is installed on the mainline before all of the valves in a group.
This cost-saving measure allows a single pressure regulator to be used for
several valves.
To operate accurately the adjustable-type
pressure regulators require a pressure drop between the inlet and outlet of the
regulator. The amount of pressure drop varies depending on flow, at low flows
less drop is required. As a general rule most regulators will work well if you
set the pressure at least 1,4 bars (15 PSI) lower than the inlet pressure. If
the pressure drop is less than required, the regulator tends to not work as
accurately, and may allow the pressure to vary up and down considerably.
Using a Valve as a Pressure Regulator:
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| Brass
adjustable-type pressure regulator. The large silver bolt on top is turned to change the outlet pressure |
Using a Valve as a Pressure Regulator:
Can I reduce the pressure by partially opening
the control valve and not use a pressure regulator? This is a common question,
and the answer is yes, you can. If the water pressure from your water source
does not fluctuate, and the temperature of the valve does not change, a
partially closed valve will work just fine. A pressure regulator is nothing
more than a valve with a pressure sensor attached to it. The sensor opens and
closes an internal valve in the pressure regulator to keep the pressure at the
outlet constant. So yes, you can use a partially closed valve to reduce the
pressure, however you need to be aware of the problems this can cause.
Sometimes the vibration of the water passing through the valve will cause the
valve to open or close a little over time. The biggest problem occurs when the
water is warmer or colder than the valve.
The valve will change temperature as
the water goes through it and expand or contract, this results in a change in
how much water goes through the valve, and that changes the water pressure. If
the valve closes due to vibration or temperature change the pressure may be
reduced to the point the drip system stops working correctly and the plants
don’t get watered. If the valve opens too far the water pressure will be too
high. This results in emitters popping out of the tubes and tubing sections
blowing apart at the fittings where they connect together. Often when the tubes
blow apart they whip around, spraying water all over the place. The worst
situation is when there is an open window nearby and the water sprays into the
house through the window! So if you are willing to live with those risks, you
can use a standard valve in place of a pressure regulator. All you do is open
the valve slowly until the pressure desired is obtained downstream of the
valve, then leave it at that setting. I suggest periodically checking the valve
and water pressure to make sure it has not changed.
Filter:
The filter cleans the water. You should use a
filter. Some companies tell you their products don’t need a filter when used
with city water, or that it is optional. Optional at the expense of your future
time and money! Save yourself dead plants and lots of grief and just install a
filter. Drip emitters have very small openings that are easily clogged. Water
piped to your house is not free from stuff that will clog your emitters! It
contains small grains of sand, bits of rust and scale from pipes, even very small
snails (the size of a grain of sand) are very common in city water systems.
I suggest that you use a filter with a 150
mesh screen or one with a higher mesh number like 200 mesh. A good quality
filter may be installed before the valve or pressure regulator, but the
inexpensive filters often sold for drip systems should be installed after the
pressure regulator. A good filter will have a maximum pressure rating of 10,3
bars (150 PSI) or higher. If the package does not list the pressure rating it
is probably an inexpensive low-pressure model.
I like to use a top quality filter and install
it right at the water source so it protects the control valves and the pressure
regulator too. Most valve failures result from sand or rust particles clogging
the tiny passages inside the control valves! As long as you need to use a
filter, why not get a good one and have it protect the valves too? It will
probably pay for itself within 5 years by preventing a valve failure! Use a
filter that is the same size as, or larger than, the valve. For more
information there is a separate, free, tutorial on filters. Click
here for the Filtration Tutorial.
Emitters:
The emitters are what controls how fast the
water drips out onto the soil. Most emitters are small plastic devices that
either screw or snap onto a drip tube or pipe. Some models are preassembled as
part of a tube. The most common emitters sold emit 4 liters/hour (4,0 l/hr) of
water. That’s about 1 gallon per hour (1 gph). There are many different types
and brands available, they each have advantages and disadvantages listed in the
detailed page on Drip Emitters. Click
here for
detailed information on what type of emitter is best for your drip system.
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| Drip Emitter on a tube (If you guessed the plants are strawberries, you guessed correct!) |
Mainline:
The mainline is the pipe that goes from the
water source to the control valves. In the illustration of a very simple drip
system above the gray colored vertical pipe under the valve is a very short
mainline. The mainline pipe may be made of galvanized steel, copper, SCH 40
PVC, SCH 80 PVC, Cl 315 PVC, Heavy Wall Polyethylene (SDR 7 or SDR 9) or PEX.
PVC is damaged by sunlight and should be buried or protected. Apply several
heavy coats of paint or wrapping PVC with aluminum tape if it is above ground.
Polyethylene has a low burst pressure and should only be used for mainlines
where local conditions are appropriate and water pressures are lower than 3,5
bars (50 PSI). PEX pipe is a special type of polyethylene made for use with
higher pressure, often sold as a replacement for copper tube. It may be used
for a mainline, however, be aware that due to a much smaller inside diameter it
has poor flow qualities when compared to copper. I recommend that when using
PEX you use one tubing size larger than you would use for copper tube.
On large
drip systems a single mainline might lead to several control valves located at
different areas of a yard. On large properties a mainline will be install in a
loop around the perimeter of the property. Because the water in the mainline is
always pressurized, hose bibs are often installed on the mainline. On a large
property with a looped mainline hose bibs are often installed on the mainline
at 30m intervals (100 feet) around the property to allow for use of hoses. I
like to foliar fertilize my plants using liquid fertilizer from a hose-end
applicator, and the hose bibs make this easy.
There are also devices called
“quick coupler valves” that are essentially a water outlet that is mostly
underground. You plug a special coupler with a hose attached to it into the
quick coupler valve. They are typically only available from on-line retailers
or local irrigation specialty stores. I use them in most of my commercial
irrigation systems, the maintenance folks love them.
Lateral and/or
Sub-Main:
The lateral is the pipe located between a
control valve and the drip tube. Some people use the name “sub-main” for this
same pipe. I used the term sub-main in the first version of these guidelines,
but have decided to use lateral now to avoid confusion with the names used for
sprinkler systems. The lateral pipe may be PVC, PEX, or polyethylene. The
lateral is located after (downstream) of the pressure regulator so it is not
necessary to use a pipe with a high pressure rating. Class 200 PVC or standard “polyethylene
irrigation pipe” work good for laterals. Class 125 PVC may also be used but be
careful as it breaks easily. PVC is damaged by sunlight and should be buried or
protected. Apply several heavy coats of paint or wrapping PVC with aluminum
tape if it is above ground. Many small drip systems do not have laterals, in
those systems the drip tube connects directly to the control valve.
The
illustration of a very simple drip system at the top of this page shows a
system without a lateral. Laterals are often used when multiple drip tubes are
needed, such as when the irrigated area is too large for a single drip tube.
For example a single lateral or multiple laterals might extend from a single
control valve to several drip tubes located in different areas of a yard.
Two different thread types are typically found
on 3/4″ drip equipment. Hose threads are the type of threads
found on garden faucets and garden hoses. The female side will have a soft hose
washer in it to seal the connection. Typically they also have a swivel device
on the female side, but not always. Pipe threads are the type
of threads found on standard pipes. It’s really confusing, unfortunately, and
it is not easy for someone without experience to just look at the threads and
tell them apart!
How to identify hose threads: If there is a washer inside a
3/4″ female fitting that is a pretty good sign it is a hose thread. (Although
there are some specialty fittings that use washers and have pipe threads. For
example; sink water supply hoses.) When looking at male threads, hose threads
have threads that are slightly larger and are farther apart from each other.
There also tend to be a smaller number of threads when hose threads are used
and the threaded section of the fitting tends to be shorter. (See photo below.)
If you look at male pipe threads you will notice there is a slight taper to the
threaded area, the end has a slightly smaller diameter than the back (look real
close at the male threads on the left side in the photo below, you can see the
diameter increases slightly as you move toward the right.) This works a bit
like a tapered cork for a bottle. The taper forces the male pipe threads to
bite into the female pipe threads, helping seal the joint as you tighten the
connection.
Connecting hose threads to pipe threads: It is best to use a special
adapter made to connect them. When you try to connect hose threads directly to
pipe threads, it will start out fine and will seem like they fit. But once you
get past a couple of full turns you will feel considerable resistance because
the threads don’t match. Sometimes with plastic fittings they can be forced
together, but most often if you do this the connection will leak (if you force
them together there is a good chance of causing unrepairable damage!) A trick
that sometimes works for a quick fix when connecting a hose thread to a pipe
thread is to put two washers in the joint rather than one. A much better way is
to use a special adapter made for the conversion (see photos of adapters
below.)
Hose to pipe adapters: They make adapters that have
hose threads on one side and pipe threads on the other. They are available in
many combinations: male hose to male pipe, female hose to female pipe, as well
as male to female versions. There are also versions that convert to 1/2″ pipe
threads rather than 3/4″. Any good hardware store should have at least a couple
of these combinations available. A good suggestion is to “mock up” your
connections by screwing them together slightly in the hardware store before you
buy the parts. That way you know they will fit. To help you read labels, common
abbreviations used in hardware stores are
- MHT = Male Hose Thread
- FHT = Female Host Thread
- MPT = Male Pipe Thread
- FPT = Female Pipe Thread
- Pipe = Pipe Thread
- Hose = Hose Thread. Remember to use Teflon tape sealer on male pipe threads to prevent leaks. Avoid liquid pipe thread sealants on irrigation systems, excess sealant breaks loose inside the pipe and clogs the emitters and sprinklers. You don’t need Teflon tape on hose thread connections, they should have a hose washer that seals them.
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| Pipe Thread to Hose Thread Adapters Pipe threads are on left, hose threads on right Top is a MPT x MHT adapter, bottom is a FPT x FHT adapter |
Drip tubing is a special tube used in most
drip systems. The tube is laid on the ground surface between the plants. The
emitters are installed on this drip tube. Drip tubing is a thin-wall
polyethylene tube (thinner than standard polyethylene hose), has a low pressure
rating, and is generally produced in metric sizes. Sometimes it is called drip
hose or drip pipe. Common sizes are 12 mm (0.455″ or 3/8″), 16mm (0.620″ or
1/2″), 18mm (0.720″ or 1/2″), and 24mm (0.940″ or 3/4″). Do you see the problem?
Two sizes are commonly referred to as “1/2 inch” in the USA! The fittings for
these two are not interchangeable. So make sure you know what
you’re getting when you buy it! Do not bury drip tubing underground- gophers
and moles love to chew on buried drip tubing! Some drip systems do not use drip
tubing.
These systems are commonly called “hard-piped drip systems” and are
used mostly for very high quality drip systems in commercial landscapes. On a
hard piped drip system the emitters are installed directly onto the laterals.
This requires special emitters with threaded connections rather than barbs. For
a drawing showing how a hard piped emitter works click
here.
Drip
Tube Fittings:
Fittings (including tees, couplings, ells, and
adapters) are the plastic connectors used to attach the drip tube to other
tubes, to control valves, or to pipes. Important- make sure the fittings are
the exact right size! Using fittings made for a different tubing size will
result in the tube blowing out of the fitting. 9 times out of 10, when a tube
blows out of a fitting it is because the fitting is the wrong size. If you use
a 15mm fitting on 16mm pipe you are going to have problems. Remember, both 15mm
and 16mm tube are often labeled as 1/2 inch size in the USA!
Barb type fittings insert into the drip tube.
Generally they should not require the use of a hose clamp to hold them on, if a
clamp is needed the water pressure is too high or the fitting is the wrong
size. The advantage of barb fitting is that they are generally easier to
install than the compression type. The disadvantage of the barb type is that as
the tube goes over the barb it is stretched, which weakens the tube. The
weakened tube will sometimes split open at the barb after a few years,
especially if exposed to sunlight. OK you ask, if barbs are a problem then why
do they use barbed fittings with standard polyethylene pipe? Standard poly pipe
has a much thicker wall than drip tube and doesn’t stress as much when
stretched.
You also clamp standard poly pipe to the fittings, which helps keep
the pipe from splitting (that’s why you need to clamp poly pipe even if it seems
to stay in place without the clamps). Drip tubing is not clamped to the
fittings (clamping doesn’t help prevent splitting because of the thin drip
tubing wall).
Compression type fittings are basically the
reverse of a barb fitting. The tube slides inside the fitting, where an
internal barb compresses the tube and holds it in place. The advantage of
compression fittings is that they do not stretch the tubing, so they are not a
cause of premature failure of the tube. Once the tubing is inside a compression
type fitting it is very difficult to remove.As a general rule, barb fittings are best used
for buried or covered tubing (the tube is not exposed to sunlight) and
compression fittings are used for tubing that is not buried.
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| Drip Tube Fittings Left: Barbed Type Right: Compression Type |
Lubrication: Some people just don’t have the
strength to shove the tubing into a compression fitting. First make sure the
fitting is the right size, as that is very often the problem. If it is, then
you can use a water soluble lubricant on the tube. Do not use oil, silicon
sprays (WD-40) or soap! Absolutely do not heat the tube with a flame, hair
dryer, or hot water as that will stretch the tubing and create weak spots!
What’s a water soluble lubricant? Try a product called K-Y Jelly. Attention
guys! Avoid terminal embarrassment! Do not head for the hardware store for K-Y
Jelly. Try the drug store, err, lady’s personal hygiene department. Might want
to take along the wife. Need I say more?
Spaghetti,
Feeder, and/or Distribution Tubing
Feeder Tubes, Spaghetti Tube, and Distribution
Tubing are all names used for small diameter poly or vinyl tubes, anything less
than 10mm (3/8 inch) in diameter. I love spaghetti to eat, but I hate it for
use in drip systems! The problem with these small tubes is with maintenance.
These little tubes tend to be easily cut, broken, pulled loose, etc. and are
generally a nuisance. This small tube is often connected to the outlets of
multiple-outlet emitters. This tubing is the reason I do not recommend the use
of multiple-outlet emitters.
If you are a meticulous type person who can be
very careful, do your own yard maintenance, and you don’t have pets or kids in
the yard, you may not have any problems. But for most of us, regret soon sets in
as repairing these small tubes becomes a weekly maintenance chore. There are a
couple of exceptions where the tubes work well. One is when they are stapled
above ground to a trellis or arbor for watering hanging plants. They need to be
firmly attached, in a location where they will not be damaged. The other is for
risers used on hard-piped drip systems.
The purpose of an air vent is to prevent air
from being sucked into the emitters when the system is turned off. When the
drip system is turned off the water in the pipes drains down to the lowest
point, where it drains out of the emitters. As the water drains out it is
replaced with air that is sucked into the tube through the higher emitters. As
the air is sucked in, dirt may also be sucked in with it. The dirt may then get
stuck and clog the emitter outlet. The purpose of the air vent is to allow air
to be sucked in through the vent rather than the emitter.
When used, the air
vent is installed at the highest point on the drip tube. It is important to
make sure that the air vent will not become covered with dirt or dirty water as
that would allow dirt to be sucked into it. Always use air vents if the drip
system is installed on a slope, as the elevation change creates a more powerful
suction that will suck in more dirt. Air vents often are not used on smaller
drip systems. If you don’t use them just make sure the highest emitters aren’t
sitting where dirt can easily be sucked into them.
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| A small air vent designed for a drip system |
Flush Valve or
End Cap:
The end cap is
important. Without it the water all runs out the end of the drip tube. (Well,
duhhh…) The water in a drip system flows very slowly in the tubes. This allows
any sediment in the water to settle out, over time a layer of this sediment develops
inside the tube and needs to be flushed out. In some climates algae may also
grow in the tubes and need to be flushed out periodically. Normally drip tubes
are flushed once a year. If you have algae problems you may need to flush the
tubes more often.
Automatic flush valves are available that flush the tubing
each time the water is turned on. I do not feel that most of these are
particularly effective. They simply do not flush for long enough or flush
enough water out to remove much, if any, sediment or algae. My preference is to
use a manual flush valve, or just use a simple hose-thread cap that you can
remove to flush the tube. Here’s a money saving tip; you can make a end
cap/manual flush valve by just bending over the end of the drip tubing on itself
to crimp off the flow. Then use some wire or a cable/zip tie to hold the tube
in the crimped position. Un-crimp and straighten the tube when you want to
flush it.
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| Tubing end crimped with a cable tie |
For very high end drip systems with
lots of algae or sediment you may want to build your own auto flush unit. This
is an expensive project requiring a high level of skill and knowledge! Manifold
the ends of the drip lines together, so that a single flush outlet can flush
the entire drip circuit. Install a anti-contamination type solenoid valve as
the flush valve on the end of the flush manifold. (An anti-contamination valve
is a special irrigation valve made for use with dirtier than normal water.)
Wire the flush valve to an irrigation controller and program it to open the
flush valve on a periodic basis, typical might be for 2 minutes once a week.
The drip circuit control valve must also be on during the flushing. So both the
control valve AND the flush valve must be activated at the same time.
Do not wire
them together on the same controller circuit as that will cause the flush valve
to remain open all the time. You will either need to use two controllers and
then coordinate the times on them, or you will need a controller that can run
two valves on two different programs at the SAME TIME. Warning; most irrigation
controllers can’t do this. I suggest you take these instructions and go to a
professional irrigation dealer and have them assist you in your controller
selection. Make sure you have someplace for the flush water to go, as it will
release a lot of waste water when the flush valve opens. Keep in mind that both
anti-contamination valves and the special controller you need to use are
expensive and this is not a very cost effective solution in most cases.
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| Drip laterals for onion nursery -Igingilanyi village, Iringa |
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| Drip lateral foe Chinese cabbage, Igingilanyi village-Iringa |
Eng Herman Nguki wa Malekela, (Irrigation & Water Resources)
ngukiherman@ymail.com
0763 639 101/0679 639 101
@Water Droplet Community (WaDCo Tanzania)
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| Thank you very much for visiting our blog, for questions you are welcome. You are invited also to visit our Facebook page (Water Droplet Community Tanzania). Eng Nguki |