Buried watering ? Before digging....

You have decided to install an underground watering system for your lawn? Before starting the work, it is essential to have a technical study carried out by a professional.

There is no need to rush into buying pipes, fittings, sprinklers... 90% of the success of your installation depends on the quality of a preliminary study on plan; this will allow you :

1. To know if, technically, you can make such an installation. Depending on the flow rate and pressure available in your home, this is not always the case!
2. To obtain a list of all the necessary supplies, without forgetting anything.
3. To be sure that the underground installation will work (maximum number of sprinklers per pipe, location of solenoid valves, installation of the programmer, diameters of the pipes to be used,...).
4. Most importantly, it will allow you to know exactly where to place the sprinklers.

You may think that this last point seems simple to address, and yet it is one of the most difficult parts to design in an optimized way.

Only a specialist, who is familiar with the technical characteristics of the various existing sprinklers, will be able to advise you on the locations that will be definitive once the trenches have been filled in.

A wrong location, and you risk to be disappointed with what you have installed by yourself.

The main risk is that the coverage (...rainfall) is not balanced. In this case, you will have to water longer than expected certain areas of the garden that are not properly covered, in order to "wet" everything.

This will result in a very high (too high!) water consumption.

In short, the correct crossing of sprinklers offers the guarantee of a uniform watering quickly, thus saving water.

This is why, once the technical study on the plan is in your hands, it is imperative not to modify what has been done, especially in terms of the quantity of sprinklers planned, and the crossing of the watering zones. As always, a sprinkler must cover a large part of the surface of its neighbor, this is the first principle to respect.

Some DIY superstores will provide you with a free technical study through their supplier.

You can also ask a professional, but the service will probably be invoiced in this case.

Once you have the technical study on plan in your hands, you can get the useful material, and start digging...

Rather than with your arms, I can only encourage you to use a rental machine : excavator, trencher...

Underground watering of a lawn from a tank

Buried watering from a tank is a recurrent question on our forum, and Nicolas, our watering specialist, brings us his analysis of the question.

"Automatic watering of a lawn from a rainwater collection tank is more of a philosophical choice than an economic one."

Example:

• You install a 6500 liters tank (2000 Euros or the equivalent of 500 000 liters of "drinking" water)
• You install an automatic watering pump, thus automated with its various safeties (500 Euros, i.e. 125 000 litres of water)

=> You must therefore consume 625 000 litres of water before you can amortize the installation (we'll skip the "various and sundry" costs that come on top of this, including the earthwork and the masonry installation for a tank, the overflow drain, the supply through the gutters, the installation and the wiring of the pump... )

After 625 000 liters of water, we begin to earn money (once again, I pass the maintenance of the installation, wear of the pump, or simply the electric consumption of a pump which must function 250 hours at best for this flow, for a motor of 1000 Watt).

325,000 liters = 156,000 m² of lawn for information.

=> Assuming that you have 1000 m² of land, you need -only- 150 days of watering to amortize the installation. But the problem is that during these 150 days of watering, there is no water in the tank. A (full!) tank of 6500 liters can automatically water 1500 m² of lawn, but the next day the tank is empty...

The use of a tank with its pump, its installation and its maintenance is rather expensive and it takes years before it is amortized, it can't be a financial choice (to save money), it's much cheaper to pay city water, especially in the short and medium term. Especially since it is possible for large plots of land to have water half as expensive by the water company (that's another subject).

A tank, even a big one, does not allow to do the underground watering of an automatic installation. A tank allows you to water your vegetable garden, to water your window boxes, to let your children play with water, to wash your car (a little), from time to time. It is a product that is often empty when you need it, and that overflows when it is winter...

The tank filled with rainwater is not a product suitable for automatic in-ground watering of the lawn unless you have a tank with a much larger reserve.

Balconies and terraces, the principle of installation for plants in pots

An automatic watering system for a terrace is very simple to install. All you need is a simple tap. A 220 volt power supply is not necessary.

Let's get rid of the idea that such an installation is only useful during your absence, for vacations: like any watering system, it is a comfort that can be used most of the year, and that allows to save water.

Most of the big DIY stores sell all the material you will need. It is very easy to install, the fittings being, for the most part, to be fitted without tools.

Principle of installation of the system

• At the beginning, a tap on the terrace.
• We place on it a "double outlet" which will allow to multiply by 2 the fittings.
• On the first one, we screw a battery programmer (use good quality alkaline batteries: Varta or Duracell for example).
• The second outlet will remain free and autonomous in order to easily wash hands, fill a bucket...
• After this programmer, connected by a piece of garden hose, come the filter and the regulator.
• The filter prevents particles from blocking the small sprinklers placed in the pots (or planters).
• The pressure reducer is used to lower the pressure and regulate it. All the rest of the installation works in low pressure: from 1,5 to 2,5 bars.
• Since the installation is now in low pressure, it is necessary to unroll polyethylene pipe of diameter 13x16mm (in the Garden department, in GSB).
• For the terraces made on slabs, it is possible to pass this pipe underneath: the discretion of the installation is then total.
• At the end of the pipe, put a small stop valve rather than a plug, this allows to drain the pipe before winter: once the pipe is emptied of its water, the major part of the installation remains in place outside.
• From this main 13x16 pipe, we will create many branches, to go up in each pot, with small 4mm (or 4,6mm) pipe. This pipe should not be used as the main supply; we cut short lengths of it (from 1 to 5 meters) which will be connected to the 13x16 pipe.
• Finally, at the end of the small pipe, a dripper or a micro-sprinkler (usually reserved for very large containers) is installed. The installation must include one or the other. I strongly advise against mixing these two sprinklers, which are very different in terms of the amount of water they deliver.
• The only thing left to do is to fix the dripper with a small spike (or ground spike) so that it does not touch the ground directly but is slightly raised.

Tips for use

Set the timer for watering late in the evening, ideally at night, or early in the morning. If the trays can't hold water, why not do three short waterings...? With a good battery, you can water several times a night, for more than six months, without ever changing the battery.

But before winter, bring in the timer, remove the battery and put in a new one the following year.

With a simple installation like this one, you save time, peace of mind, you use less water than with your watering can, with a much better result.

Make several watering networks

You now have the technical study in hand in order to realize the underground watering of your garden. Therefore, you will probably have to make several watering networks.

Indeed, from a single source of water supply (tap, pump ...), the flow (volume of water) and pressure (speed of water circulation) will not be sufficient to operate all the sprinklers in your garden at once.

It is therefore necessary to distribute this power in several successive stages, which will water one after the other: in cascade. When the first part will have finished its cycle, the second part will start, then at the end of the second cycle the third...etc.

To do this, we must create an important part of any underground watering installation: the solenoid valve manifold [see photo above ].

This manifold (also called "clarinet") is composed of various parts :

• the single water inlet pipe, coming from your pump or your faucet, with its fitting
• 
  
• a shut-off valve (with a small bleeder) to isolate the watering from the rest of the domestic supply, for example in case of repairs on the installation. This valve can be placed well before on the water supply pipe, but regardless of its location, it is essential. That is why it can be found at the entrance to the collector, but often it is located in the basement, in the garage ...
• Union fittings: these have various shapes (elbow, cross, tee...). For a few years, they are now easily dismountable and do not require any sealing product such as Teflon. They allow all kinds of assemblies, depending on the number of networks to be made and the desired configuration. The main advantage of these fittings is the fact that disassembly for repair is significantly simplified.
• The solenoid valves: this is the nerve centre of the installation. These are the parts that open and close on command from the programmer.
• Since they will operate in cascade, the number of solenoid valves is not limited. Logically, you should install as many as you need.
• You must connect them and the pipes that go out into your garden.
• The whole thing will be placed outside, under the ground level, in a manhole which is provided with a green cover: this one will be discreet, even implanted in your lawn
• Finally, it remains to install a multi-strand electrical cable near the collector, to connect the solenoid valves to the programmer in a watertight manner.

As a finishing touch, you can put a little gravel at the bottom of the manhole, this allows the water to drain.

Now you can water your whole garden with one hose, but in several steps: the programmer and the solenoid valves work for you at night.

Automatic watering

With the arrival of the vacations, you start to wonder how you will find your garden and your indoor plants when you return. You think of your family, neighbors or close friends to come and visit your garden in your absence but they are not always available and you would rather not bother them with your garden.

There are several solutions. From the most rudimentary to the most sophisticated and this going with that from the most economical to the most expensive, you will find a solution to your expectations and your budget.

The D system

The economic solution par excellence and within the reach of everyone. It is not a question of cleaning up the garbage in your neighborhood but simply keeping your empty plastic bottles in order to reuse them as water reserves.

The principle consists in placing bottles filled with water upside down, with the neck in the ground. The watering is then done naturally by gravitation according to the humidity of the ground. All sizes are allowed: 0,5l - 1l - 1,5l - 2l - 5l.

Ideal solution for outdoor use, for your vegetable garden and your flower beds. 2.

Pots or tubs with reservoir

We will not dwell on this solution which is ideal indoors but whose aesthetics are sometimes questionable.

Outside, it finds its limits beyond 15 days of absence. Ideal for your geraniums of balconies, terraces, your jardinières of ornamental plants.

Carrots

It is not a question there of sowing rows of carrots but of setting up water diffusers whose shape evokes the vegetable of the same name. They are connected to a reservoir that supplies them with the necessary water.

This water tank can be any container: a bowl, a plastic bucket,... The volume must be in relation with the duration, moreover cover it to avoid too much evaporation.

Ideal: indoors and outdoors, for plants in isolated pots that should be grouped around your water supply. It is also suitable for planters without or with a reservoir (to which it can be added).

Tip: when outside, place a second hanging planter opposite your hanging planters and fill it with water. Your balcony will stay in bloom in your absence.

Watering systems

Automatic watering systems allow you greater flexibility in managing your watering with the possibility of

• adapt the flow rates according to your plants
• program the frequency and duration of watering

However, they need to be installed 15 days before your departure in order to check that they are working properly and that the volume of water poured is adequate for the needs of the plants.

This solution is the most expensive. However, when considered in the context of daily watering of your garden, it becomes by far the most interesting.

The watering system with a pump

The watering system consists of

• a transformer with a built-in programmer
• a low voltage pump immersed in a water tank
• a network of plastic pipes
• micro-drippers (several flow rates are available)

The capacity of the water tank is to be sized according to the water needs in your absence:

Volume of the tank = Watering frequency x Flow rate of the micro-dripter x Duration of watering x Number of micro-drippers x Duration of your stay

Ideal: indoors if you do not want to move your plants. Advice: don't hesitate to place larger sub-pots or even to put pot covers for the eventual overflow.

The watering system connected to the faucet

The watering system consists of

• a programmer screwed to your water tap: the price varies proportionally to the possibilities offered
• a pressure reducer to limit the pressure to 1.5 bar
• a network of plastic pipes of several diameters.
• cross, tee and Y fittings
• micro drippers (several flow rates are available) - various micro sprinklers:
• for trays ......................... to 360º.
• stopcocks to isolate your watering installation by zone. This will allow you to intervene on a zone of your garden while maintaining the watering of the other zones. Recommended for isolating the circuit dedicated to planters and pots during their wintering period.
• Flow regulators

To create your network without too much pressure loss, start with the primary network composed of large pipes. It is the backbone of your network and guarantees sufficient pressure in the most remote areas. Consequently, it must cross all the areas you wish to water.

Note that in the case of very remote areas, it is advisable to provide a service to the primary network(s) by buried reinforced pipes. The pressure reduction will then only take place at the connection with the primary network.

Then install the secondary network made up of thin pipes, a real local service for your different plants.

Ideal: outdoors, if you plan to use it as a year-round watering solution for your garden.

Advice: install your programmer on an outdoor faucet to prevent flooding in the event of a hose rupture or if a connection breaks.

Otherwise, water your garden and your indoor plants before you leave, nature will do the rest.

Drip irrigation

Economical and ecological, drip irrigation is the solution of choice in the garden and even on a balcony. Coupled with a programmer, you will no longer have to worry about watering your plants so that they are beautiful and healthy!

What is drip irrigation?

• It is a low-pressure micro-irrigation system that starts with a simple water tap that feeds the main circuit consisting of a pressure reducer, a hose that carries the water to the plantations (diameter 16 to 25 mm), and then secondary circuits that can be made with thinner hoses (diameter 4 to 6 mm). The available hose lengths range from 5 to 100 m.
• Drip irrigation is usually coupled with a programmer that allows you to plan the watering times. The connected programmer offers even more freedom to the gardener.
• Note that there are watering kits that do not require a faucet or electricity. They are interesting in isolated areas or in the context of an unoccupied second home. They work from a rainwater collection tank, by gravity. The programmer is powered by batteries or even a small solar panel.

The dripper, the star of micro-irrigation

Watering each plant directly at its foot by drip is the goal of this micro-irrigation watering. To do this, drippers are placed on the pipes, with a fixed or adjustable flow rate, they allow you to irrigate each plant according to its needs by providing water progressively, drop after drop (from 0 to 20 liters per hour).

Note that the drippers can be placed directly on the first circuit if the watering plan is linear and/or on the secondary circuit.

From the simplest with a fixed flow rate to drippers whose flow rate can be adjusted by rotating the head, the choice is vast. The most fastidious will turn to professional solutions such as self-regulating drippers that compensate for a too low or too high pressure to deliver the required amount of water. These drippers will also solve the problem of a very sloping ground but be careful: often, they cannot be closed if a plant disappears unlike the adjustable drippers.

There are also built-in drippers for simplicity, but they do not allow the same creativity as a system where the gardener chooses to install his drippers according to the positioning of the plants already in place. Built-in drip lines have a spacing of 15, 30 or 50 cm, so it will be necessary that the garden is not yet planted or that the plants are exactly at these spacings for the system to be effective. However, this type of hose is easier to install and saves a lot of time.

What are the advantages of drip irrigation?

• This type of irrigation is very localized and ensures the preservation of water resources, the interest is both ecological and economic. Indeed, we count a saving of about 25 to 40% compared to a traditional watering for an efficiency 40 to 50% higher.
• The plants are watered at the right dose and in a regular way, which avoids the hydric shocks which weaken them in case of forgotten watering.
• The water is brought under low pressure to the feet of the plants and penetrates slowly towards the root system which benefits directly from it.
• The foliage is not watered, which avoids many cryptogamic diseases or leaf burns.
• The possibility of programming the watering offers a newfound freedom for the gardener who can finally go on vacation or take care of other activities.

How to install an efficient drip irrigation system?

Flow rate and pressure are the basic concepts of drip irrigation.

• Depending on the diameter of the hose, the flow rate will be more or less important. It is therefore crucial to calculate the necessary flow rate for the number of drippers installed and the length of the pipes.
• The flow rate of each dripper is given for a pressure of 1 bar (achievable thanks to the pressure reducer installed at the faucet outlet). For example, if you want to install 10 drippers with a flow rate of 2 l/h and 20 drippers with a flow rate of 4 l/h on your circuit you will need a total flow rate of 100 l/h. It is always better to limit yourself to a maximum of 50 drippers per circuit.
• A 16 mm diameter pipe will be chosen for a circuit of 50 to 100 m length, beyond that a 20 mm diameter pipe will be necessary so that the flow is always correct at the end of the circuit.
• Always differentiate between circuits with drippers and circuits with sprinklers. To do this, you can divide your irrigation plan into several circuits using directional elbows, bypass tees, plugs to complete a circuit...
• Don't forget to think about the solenoid valves needed to create several separate circuits. These solenoid valves, placed at the beginning of each circuit, are programmable. They work either under electrical tension via a programmer, or individually thanks to batteries. The solenoid valves allow you to operate each circuit independently.
• If your irrigation system has only one circuit, a timer will be installed just below the faucet to control the frequency, duration, and timing of watering automatically.

What is the best frequency to program a drip irrigation?

Watering should preferably be scheduled in the late evening after sunset so that evaporation is reduced and the plants get the most out of the water.

If each dripper corresponds to the real need of the plant, the watering can be started during one hour every evening in summer. In dry and hot weather, it can be extended by one hour. Only experimentation will help you decide on the duration and frequency, as each garden is exposed differently and exploited in different ways (presence or not of mulch, weeds...). It's up to you to learn how to dose, and to enjoy your tranquility!