Technical
Irrigation shutdown
Don’t be caught out in the cold
Reesink Turfcare’s senior technical support for Toro Irrigation, Rob Green, provides a blow by blow account of winter system shut down
T
he UK’s winter runs from 21 December until the 20 March, and it is predicted by The Met Office that it will be the coldest in five years. In many parts of the world, irrigation shut‐down has to be performed as part of regular winter maintenance; however, with UK temperatures hovering around freezing and not going much below, it is not always deemed necessary here. But, with the country plunging into arctic conditions and temperatures predicted to be as low as minus 11O
C, Reesink Turfcare
senior technical support, Rob Green, says it’s not too late to protect irrigation systems against the cold and frost if you delayed or decided against the winter shutdown procedures in the late autumn.
The most effective way to prevent damage due to arctic freezing conditions is to completely drain or shut down the system. The majority of water needs to be removed from the system’s pipes and sprinklers so that it doesn’t freeze, and gives room for expansion to prevent bursts.
There are a couple of ways of approaching this, with the most common in our territory to drain via gravity or with compressed air in colder climates (also referred to as a system blow‐out). Whichever option you choose, the first step in the process is to turn off the water!
By draining
The first and most important operation is to isolate the irrigation pump or pumpset, removing bleed pins etc. and isolating the power supply to prevent damage if they are accidentally switched on. The suction pipework will need isolating and draining down (if above ground) to prevent frost damage along with the delivery section of mains. Under normal circumstances, these sections of pipework will have drain valves fitted to allow this operation to be carried out. If these are not available, then loosening of the suction and delivery pump fittings will provide the same outcome, by
removing the pressurised water. It is also a good idea to keep some form of heating (on a thermostat) within the pump room to keep temperatures above freezing. Out on the course, you will need to locate the manual drain valves which should be highlighted on your irrigation ‘as laid’ plan for easy access. These will all need opening once you have isolated the pumps as previously mentioned, but don’t forget to go back and close them slightly to prevent pests such as rodents entering the pipe network and causing problems when you pressurise the system in spring. At this point, you will start to see the majority of the water escape from the pipe network into drains and ditches, but you are only half way there in terms of closing the system down. Now comes the leg work… To effectively remove pockets of water remaining in the system, you need to locate all the hosepoints in each valve box and open them slightly to remove the ‘suction effect’ and allow trapped water to drain away and give room for expansion. Again, remember not to open the valves completely or those pesky rodents could find another way to access the pipework.
Whilst entering a number of these valve boxes, you will also find the solenoid valves that operate the sprinklers. We recommend that each of these valves have their bleed pin removed to assist with draining the valve assembly, but remember to leave the pin somewhere safe and visible otherwise this can be an expensive operation in the spring when you can’t find them!
When it comes to the sprinklers, you usually find that most systems are block control on the tees, with all other areas valve‐in‐head. This makes the block systems easier to drain down because you have already removed the bleed pins from the solenoid valves, allowing water to flow freely. Finding the lowest sprinkler (if available) and lifting it manually for a period of time allows for any pressurised water to be released from the pipe network and,
PC DECEMBER/JANUARY 2018 I 127
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