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Gravity Fed Irrigation systems

This year we've been blessed with heavier than usual rainfall but in years when water conservation measures are necessary, gardeners take the brunt of media attention. This despite the fact that a relatively small proportion of all domestic water is used for our gardens. Hose pipe bans, water meters and requests to conserve water should motivate us all to collect rain water in a water butt or tank.

The ideal location for a water butt is fairly high up. The roof of a sturdy, flat roofed shed or garage are possibilities. Take great care though as, once full with water, even a relatively small container is very heavy! The guttering and downpipes from the main roof may then need some modification to divert as much rain as possible to your collector. During a prolonged drought the system will need topping up, preferably using so called "grey water" from washing, bathing, washing up etc. This is perfectly acceptable for watering trees and will even have a deterrent effect on greenfly.

Small, gravity-feed systems, fed from a suspended waterproof bag are available, but these only cater for a few trees for a short period. They can supply drippers or better would be an absorbent layer beneath the pots (such as capillary matting with a wick through the drainage hole. This gives just about the right amount of water for survival, without waterlogging.

Recently, very large plastic containers have become available. Some of these tanks have been used to import orange juice and are now recycled rather than being scrapped. They are very cost effective compared to smaller rainwater butts and the amount contained (1500+ litres - 360+ gallons) should easily deal with the needs of a small garden or tree collection through a drought. They weigh tonnes when full and must have a suitable foundation built. These stand 2 metres tall and can provide a sufficient head of pressure to operate a simple irrigation system. If raised on a plinth or installed at the top of a sloping garden there may be sufficient pressure to operate sprinklers. Alternatively they could be sunk in the ground (a fairly major undertaking as the hole would have to be 2M deep and 1.5M wide) and the water pumped out. Suitable 12 volt submersible pumps are available and, if desired, these could be run off a battery charged by a solar panel. All the equipment necessary is available from companies such as Rain Tanks.

Distribution to your trees should be through pipes of hose pipe diameter reduced to smaller diameters for the individual runs. Compare the prices of materials such as aquarium air-line piping, connectors and valves with the dedicated Gardena, Hozelock or Tropf Blumat irrigation systems available in garden centres. Their sprinklers, drippers and misters are best purchased, as they are well designed and fully adjustable. Test aquarium hose to ensure a correct fit with the attachments before purchasing.

Automated Irrigation Systems

An irrigation system can be controlled manually, switching on and off by tap as required. The full potential of an automated system is that it caters for the needs of your trees in your absence and saves a lot of time that could be better spent on refining your trees. A DIY automated system can be manufactured if desired. A washing machine solenoid valve is operated by mains voltage and controlled by a time switch. The valve may be purchased from a washing machine spares shop or repair centre. The time switch is of the cheap and simple type that can switch a light on and off when you are on holiday. \par \par A major disadvantage is the safety consideration. Mains power and water do not safely mix! The wiring and box containing the valve must be waterproof and installed safely. If you are not a competent electrician, it would be wise to secure the services of someone who is, or at least have your handiwork checked over prior to use. The advantages of this type of system are that it is cheap, less than half the cost of a dedicated system and it doesn't rely on a battery.......

Ready Made Irrigation Systems

Several manufacturers now produce a range of semi and fully automated irrigation systems. Gardena, Tropf Blumat, and Hozelock, are among the better known. They each provide a bewildering array of pipes, valves, connectors, pressure reducers, sprinklers, sprays, drippers, dribblers, misters etc. Water computers are available to perform the switching on and off at pre-set intervals. Make sure that the manufacturer produces the parts that you require and then buy according to the best pricing. Check the larger DIY stores as well as garden centres.

Photo of Jim Smith's shade house Click for a closer look at the irrigation setup in Jim Smith's shade-house.

Water Computers

These perform the same function as the DIY version described above. There are several models available from the manufacturers already mentioned. Check that the ones offered do all that you require, before investing. They are generally operated by a battery powered electric clock that controls the opening and closing of a solenoid valve.The water computer is fitted direct to the garden mains pipe or to a pressure regulator attached to the main. Either system can easily be attached to an existing outdoor rising main or tap. If you cannot hide or disguise the water computer it would be sensible to make certain that it is very securely fixed. Some manufacturers provide secure bolting kits to attach it to a wall.

Once the battery has been installed and the set up procedures have been followed, the systems can water for different periods at different times on each day of the week if necessary. If you have a small number of trees you could set up a system that has an adjustable dripper in each pot. For larger numbers of trees, or seedlings and cuttings growing on, sprinklers that cover a wider area may be a better option.

Photo of pipe junction with jubilee clamps

Be aware though that sprinklers distribute water over a circular area. Most of the water falls towards the outer edge and the least nearest the centre. This characteristic can be used to advantage. Place trees needing the most water on the outer periphery and those needing less, such as pines, in the centre.

I set up an automated system, prior to the drought in the summer of 1995. After installation it was checked thoroughly and it performed admirably, switching on and off twice a day, saving me an hour's watering daily. After a month of testing, the system was left to cater for the watering needs of my collection, during a fortnight's holiday. I asked my neighbour to keep an eye on the system for me. As he had previously watered all the trees for me, in my absence, he appreciated the time-saving and also knew what to look out for. He was so fascinated by the system he got up early in the morning to watch it switch on!It proved to be a sensible precaution as one morning he noticed a drastically reduced flow. On checking, he found out that a pipe union had pushed apart. Without his inspections and subsequent repair, the whole system would have failed and no doubt I would have lost a major proportion of my collection.

Another failure occurred shortly after I returned, when one of the sprinkler heads, which screws onto the end of a small bore distribution pipe, worked loose and popped off. The resultant fountain was instantly obvious and easily cured once the sprinkler was located in the shrubbery! A small jubilee clamp now secures each pipe union and sprinkler. These are the only weaknesses that I have experienced in three years.An optional extra is a moisture sensor. This is a probe that checks the level of moisture in the pot and will prevent over or underwatering. Its effectiveness is limited to the pot in which it is inserted, so a fairly average sized one will have to be selected. If a small one is metered, all the trees are likely to be watered too often. A large pot dries out more slowly and if used for the sensor, the smaller pots are likely to receive too little water.

Photo of programmable Water timer

Seep hoses are permeable pipes that allow a steady thin flow of water through the wall of the tube. They are less controllable than drippers and sprinklers and not really suited to pots. They can work well with seed beds and trees planted out in beds for fattening up.

If you install mains water in the garden, make certain that the pipes are buried deeply enough to prevent freezing (300mm to 500mm or 12" to 18"). Do not neglect the necessary job of insulating any exposed pipework. I speak from experience. Living near the coast, we rarely experience hard frosts, but 1995 was a year of extremes in both summer and winter. Temperatures dropped to -13 for nearly a week around Christmas. The thaw brought the delights of burst alkathene pipes and impromptu fountains in the garden.

If it is possible to turn the system off and drain it during the winter, do so. Remember also to detach, drain and store your water computer, if fitted. Frosts will damage this expensive component.

Some satisfaction can be had from devising your own system and it can have huge benefits. Rain water is soft and has few impurities. An automated system saves a lot of time with routine watering once perfected. It allows you the freedom to leave your collection with much less concern over trees drying out. It gives a completely different perspective on rainy days - your tank is filling up! You are also doing your bit for water conservation.

All Text & Photographs © Kevin Bailey 1998 - 2008

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All Text, Diagrams & Photographs © Kevin Bailey 1998 - 2008