Winterizing Your Lawn Sprinkler System
Every year, before the first freeze, the ritual of irrigation system "winterizing" becomes the
priority for most all irrigation system owners.
This is especially true for those in parts the country where the frost level extends below the depth of the
In the North, they must be completely drained and dried to prevent damage to the system components caused
by water freezing inside the pipes, sprinklers, and valves. Serious damage to the system will result
if improper or no winterization methods are employed.
The easiest way to winterize your system, of course, is to hire an irrigation contractor/professional to do the job.
Depending on the size of your system, it may cost anywhere between $50, $150 or more.
Doing it yourself will save you those dollars, and, after the first time, it should not take you more than an hour or so.
(hopefully...) If this is your first time you might really ought to consider a professional. Just be sure to follow
them around with a notepad so you can do this again next year yourself. (That's what I did.)
Even if you have drained some water out of the system, the remaining water can freeze, expand and crack the
PVC piping (rigid, white pipe), usually from fitting to fitting. Polyethylene pipe (flexible, black pipe) is used in
many freezing climates. Although polyethylene pipe is more flexible and can expand under pressure, water left inside
could freeze and rupture the pipe walls. Freezing water in the backflow assembly will damage the internal components
and could possibly (probably) crack the brass body.
To minimize the risk of freeze damage to your irrigation system, youll need to "winterize" your
Irrigation systems in areas where "winterization" is mandatory are installed using one of three types of
water removal in mind: manual drain, auto drain, or blowout. If you dont know your system type, it would be best
to use the blowout method.
Manual Drain Method
Use when manual valves are located at the end and low points of the irrigation piping. To drain these systems,
simply shut off the irrigation water supply (shut off will be located in the basement and will be either a gate/globe
valve, ball valve or stop and waste valve - see drawings below) and open all the manual drain valves. Once the water
has drained out of the mainline, open the boiler drain valve or the drain cap on the stop and waste valve (whichever
is used in your area) and drain all the remaining water that is between the irrigation water shut off valve and the
backflow device. Open the test cocks on the backflow device. If your sprinklers have check valves youll need to
pull up on the sprinklers to allow the water to drain out the bottom of the sprinkler body. Depending on the location
of the drain valves, there could be some water left in the backflow, the piping and the sprinklers. When all the water
has drained out, close all the manual drain valves.
Automatic Drain Method
Use when automatic drain valves are located at the end and low points of the irrigation piping. These will
automatically open and drain water if the pressure in the piping is less than 10 PSI. To activate these, you shut
off the irrigation water supply (shut off will be located in the basement and will be either a gate/globe valve, ball
valve or stop and waste valve - see drawings below) and activate a station to relieve the system pressure. Once the
water has drained out of the mainline, open the boiler drain valve or the drain cap on the stop and waste valve
(whichever is used in your area) and drain the remaining water that is between the irrigation water shut off valve
and the backflow device. Open the test cocks on the backflow device. If your sprinklers have check valves youll
need to pull up on the sprinklers to allow the water to drain out the bottom of the sprinkler body. Depending on
the location of the drain valves, there could be some water left in the backflow, the piping and in the sprinklers.
In some areas you might have a combination of the manual drain system on the mainline (the pipe between the
irrigation water shut off valve and the valves) and auto drain system on the lateral lines (the pipe between the
valves and the sprinklers).
"Blow Out" Method
It is recommended that a qualified licensed contractor perform this type of "Winterization" method,
The blow out method utilizes an air compressor with a
Cubic Foot per Minute
(CFM) rating of 125-185 for any mainline of 2" or less and a PSI of 50-80. These types of compressors
can be rented at your local equipment rental yard. The compressor is attached to the mainline via a quick coupler,
hose bib or other type connection, which is located before the backflow device. To start the "blow out",
open the Test Cocks on the vacuum breaker, shut off the irrigation water supply and open the drain on the supply
line. Once the line is drained, close the drain and proceed to connect the air line. With the compressor valve in
the closed position, attach the air compressor hose to the fitting. Activate the station on the controller that is
the zone or sprinklers highest in elevation and the furthest from the compressor. Do not Close the backflow isolation
or Test Cock valves. Slowly open the valve on the compressor; this should gradually introduce air into the irrigation
system. The air pressure should be constant at 50 PSI. If the sprinkler heads do not pop up and seal, increase the
air until the heads do pop up and seal. The air pressure should NEVER exceed 80 PSI.
Each station/zone should be activated starting from the furthest station/zone from the compressor slowly working
your way to the closest station/zone to the compressor. Each station/zone should be activated until no water can be
seen exiting the heads, this should take approximately two to four minutes per station/zone. It is better to use two
or three short cycles per station/zone than to have one long cycle. Once the station/zone is dry, you should not
continue to blow air through the pipe. Compressed air moving through dry pipes can cause friction, which will create
heat and the heat could cause damage.
Once the water has been removed from the irrigation system, shut-down the air compressor and release any air
pressure that may be present. Disconnect the airline. If your backflow device, the most common backflow installed is
called a Pressure Vacuum Breaker,
has ball valves, open and close the isolation valves on the backflow device numerous times to ensure that any trapped
water has escaped from the upper areas. Leave the isolation valves open at a 45° angle (approximately 1/2 open)
and leave the test cocks open.
Pressure Vacuum Breaker
- PVB Test Cocks
- Isolation Ball Valve Inlet
- Isolation Ball Valve Outlet
Interior Point of Connection Freezing Climates
- Boiler Valve/Drain
- Irrigation Shut Off Valve
- Main Water Shut Off Valve
- Water Meter
Types of Valves
||Stop & Waste Valve
Preparing a hydraulic control system: Shut off the water supply to the
signal control tube(s) and drain the field tubing.
Outdoor mounted controllers: Leave the power on and the dial / switch in
the "Off" position. The heat from the transformer will keep the enclosure warm enough to keep condensation
from forming inside the controller enclosure. The dial in the "OFF" will keep the controller from activating
the solenoids in the field.
Indoor mounted controllers: You may either leave the power on and the dial/switch
in the "Off" position OR you may remove the battery backup and unplug the
Rain Sensors: There is not much to do to prepare the rain sensor for the winter
months. If your sensor is the type with a cup or bowl that catches water, you might want to remove the water and place
a plastic bag over the sensor. This will keep any water from accumulating and freezing in the cup or bowl area. If your
sensor is the type that uses wafers or discs, you might want to remove the wafers and store them in the garage for the
winter months. This will keep damp wafers from freezing.
The Don'ts of "BLOW-OUT" Winterization
- Don't allow the air pressure to exceed 80 PSI for systems with PVC piping and 50 PSI for systems with polyethylene
- Don't stand over component parts while the system is pressurized with air.
- Don't leave the air compressor unattended.
- Don't blow the system out through a pump. First blow out the system, then drain the pump.
- Don't leave the manual drain valves open after the blow out.
- Don't leave the indoor drain open during the blow out!
(Trust me on that one.:)