Lawn Irrigation

As we previously discussed sowing a new lawn, this month we will talk about irrigation. Perhaps we should have done it the other way around since all but the most basic systems require pipe work to be buried into the soil (talk about putting the cart before the horse . . . c'est la vie).

Physically holding a hosepipe and watering the grass is basic, and even upgrading this system with an automatic sprinkler doesn’t make this the optimum solution for all but the smallest of lawns. Firstly, unless you want unsightly hoses trailing all over your garden, they will have to be cleared away after each session, only to have to be set up again before the next session. It is also very difficult to get an even coverage of water. Furthermore, since grass that is watered from above is best done before the sun gets too high, who wants to be watering a lawn at the crack of dawn?

Remember, we are trying to get water down to at least 10cm to encourage deep rooting. This takes a lot of water, (and time), so it is probably better to consider some form of permanently installed system. These can range from very basic, manually controlled ones to systems with electronic controllers and valves that automatically turn the water on and off in different parts of the garden.

The most efficient way to get water down to where we want it is with sub-surface drip lines. But this is expensive and very labour intensive to install. Also a quality filter must be installed to prevent dirt from the water blocking the emitters.

The other two methods to consider are pop-up sprinklers and rotary sprayers; devices that sit below the surface of the lawn only to pop up under water pressure, and then retract when the watering is finished. Depending on make and model, these generally are used to cover arcs with a diameter of as little as two metres to well over 10 metres.

The trick is to ensure that one unit waters up to the opposite unit. This ensures that all of the area gets watered and, by choosing the correct sprinkler head or sprayer nozzle, it is possible to ensure that a pretty even coverage is obtained on the whole area.

Generally speaking, the larger the sprinkler unit the more cost effective it is. Bigger units mean fewer units are needed, which means less pipe work. Still, expect to pay over 50 cents for a metre of 32mm pipe and about 28 euros for a sprayer that will cover up to 10 metres. Added to this is the cost of valves, joints etc.

Will the water supply cope?

Well, we are talking about systems that use about 2.5 bars of pressure. It is very unlikely that mains fed systems will have this much pressure in the summer. If your household water is pumped, check the setting. The amount of water used is dependent on the number of units or length of drip line used. The quantity of potential water to be used in litres per minute/hour can be calculated and, again, checked against the output (Q) of the pump. If the pump is not big enough either: a) divide the area into zones which the pump can cope with; b) buy a bigger pump, or c) consider setting up a separate garden watering system with its own tank and pump. All of the systems can be bought in grades that can cope with so-called grey water.  And there is also the potential of capturing and storing winter rain water for use in the garden.