19a — Underground Pipe System for Plant Irrigation

Chapter 19, Section 2 of the House Manual explains the use of water for plant irrigation.

This Chapter 19a explains which components make up the plant irrigation system, where they are located, how these components are connected, and how they can be used, e.g., by turning them on and off.

The information in this chapter is only intended
● for gardeners, and
● for those long-stay tenants who want to actively contribute to the care of the private or community garden, mainly for plant irrigation particularly during the long dry season from November to April/May, and also
● for tenants who want to use a planter bed to grow their own vegetables and herbs.

The following two maps show the main components of the plant irrigation system.

The main components of the plant irrigation system:
ditches and ponds, one deep well with a submersible pump (SM), two water pumps (P1, P2), underground PVC pipe system (Main Lines E in blue, C in orange, W in red, and S in green)

The culverts, a bold, dark blue line on this map, show which ponds and ditches are connected for unregulated water flow

The main components are as follows:

• The public canal along the western and southern border of Baan Sammi. The water flow direction in this canal is from northwest to southeast. The canal does not carry water all year round. The flow of water into this canal is regulated by an authority and depends on the water availability in the reservoir and the water requirements of the rice fields connected to the canal. Especially in the dry season, the canal may not contain water for a long time.
• The small pond ("Pond South"), located in the southeastern corner of the Baan Sammi property. This is the only pond connected to the public southern canal by a narrow ditch and a culvert, thus enabling unregulated water inflow from that canal.
• A small pond ("Pond East"), that is farther extended by ditches and culverts to the northern ponds ("Pond North"), and by a side ditch with culverts to the large natural swimming pond ("Dragon's Paddling Pool").
• The deep well (bore), over 100 m deep with a submersible pump ("SM"), located next to the driveway and between Pond South and Pond East, and with a pipe outflow to each of these two ponds.
• Two constant-pressure water pumps ("P1" and "P2") for plant irrigation: Pump 1 with an inflow pipe from Pond South; Pump 2 with two inflow pipes, one from Pond South and the other from Pond East.
• The underground PVC pipe system for irrigation, consisting of 4 main lines: Line East ("E", blue on the map), Central ("C", orange), West ("W", red), and South ("S", green). The Main Lines East, Central, and West are connected to both pumps, and the Main Line South is connected to Pump 1 only.
• There are main in-line taps for all the main lines of the underground irrigation system. These main in-line taps are installed in above-ground PVC pipes at the pumps to allow water to flow out. Pump 1 has four main in-line taps for Lines E, C, W, and S. Pump 2 has three main in-line taps for Lines E, C, and W. As the main lines are interconnected, you need to decide first which pump to use and which of the main in-line taps to open or close.

Not shown on the map are the numerous secondary sublines with their outlet taps of the four main lines of the underground pipe system. How these irrigation outlet taps can be recognized (and should not be confused with village water outlet taps providing drinkable water) is explained in the aforementioned Chapter 19, Section 2.

There are two basic types of taps for the plant irrigation pipe system:
● In-line taps (also called saddle taps or saddle valves) are taps installed directly into a pipe (usually larger than 1/2 inch in diameter) to regulate the water flow of that pipe. In-line taps are installed in the pipe close to the water pump, so they work as the main or primary taps.
● Outlet taps (also called end-of-line taps, outflow taps, or spigots) are taps installed at the end of a water pipe for plant irrigation. They are often connected and extended for several meters by a 3/8 inch garden hose.

In-line tap (left), all the other taps are outlet taps

Explanation of the functions of the main components for irrigation:

• Water runs in the public canal for most of the year. During the dry season, the flow of water may be temporarily stopped for a few weeks or even longer than a month, and the public canal may dry out.
• Generally, the water from Pond South is used for irrigation, provided the water level is sufficient. The water level is insufficient if it decreases lower than the pipe end for water inflow to Pump 2, which can happen if the public canal runs out of water. In this case, Pond South needs to be filled with groundwater from the deep well by the submersible pump.
• Occasionally, the water from Pond East can be used for irrigation, provided the water level is sufficient. The water level is insufficient if it decreases lower than the pipe end for water inflow to Pump 2, which may happen naturally over a couple of weeks, mainly during the dry season. In this case, Pond East needs to be filled with groundwater from the deep well by the submersible pump.
• The water from the deep well (bore) is pumped up by the submersible pump for the only purpose to raise the water level of the ponds.
• Irrigation can start when, firstly, Pump 2 (or/and Pump 1) will be switched on and, secondly, the main in-line taps (next to the pumps) regulating the water flow for the three/four main lines are opened (not the other way round!). Irrigation can stop when, firstly, the main in-line taps are closed, and, secondly, the switch for Pump 2 (or/and Pump 1) is switched off (not the other way round!).
• On the main outflow pipe of Pump 2, each particular main line (E, C, and W) can be regulated independently by turning on or off the relevant in-line tap. On the main outflow pipe of Pump 1, each particular main line (E, C, W, and S) can be regulated independently by turning on or off the relevant in-line tap. As three main lines, E, C, and W are connected with both pumps, the in-line taps for E, C, and W can be turned on at one pump but must be turned off at the other pump.
• On Pump 1, there is an additional (second) outflow pipe with an outlet tap, but it is not connected to an underground line. This outlet tap can be turned on for extra water flow, so the pump can work uninterrupted.
• On Pump 1, there is a half-inch PVC underground pipe with an in-line tap that connects to the outflow pipe of the pump. This half-inch pipe bears the word "village" next to its in-line tap, and it is connected to the village's tap water supply system. This in-line tap must remain permanently turned off. Only in the very rare case where all the pumps are out of work for days, and some plants in the garden need drip irrigation to help them survive a long drought, this in-line tap can be turned on to water the plants with village water for a limited time.

The standard operation mode of irrigation is by using Pump 2 with water from Pond South. The starting and finishing irrigation of this mode is explained below. Any other mode, e.g., using Pump 1 instead, is similar and explained in one of the sections below.

How to start irrigation using the Main Lines E, C, W, and Pump 2 with water from Pond South?

1. Go to Pond South: Check out if the water level in Pond South is sufficiently high.
2. Go to Pump 1(!): Check out the main in-line taps of the Main Lines E, C, W, and S at Pump 1: The in-line tap S can be open, and only one of the other three in-line taps (E, C, W) can also be open. This would allow the water to flow through Line S if Pump 2 is operating.
3. Go to Pump 2. The two in-line taps of the water inflow pipes for Pump 2 from Pond South and Pond East are still closed.
4. Switch on Pump 2.
5. Turn on the in-line tap of the water inflow pipe from Pond South (standard operation mode; the in-line tap of the water inflow pipe from Pond East remains closed). Almost simultaneously open the main in-line taps of the Main Lines E, C, or/and W.
6. Now, water flows through the pipes of the main lines and sublines to the outlet taps.
7. Go and open any of the outlet taps of the main lines/sublines, so you can start with the irrigation of plants.
8. As the power of the constant-pressure water pump (P2) is limited to 350 W, the water output volume decreases with every additional tap that is turned on. If maximum sprinkler output is required, no more than two sprinklers should be in operation at the same time, ideally on different water main lines. With drip irrigation, almost any number of taps can be opened fully or partially.

How to stop or finish irrigation using Main Lines E, C, W, and Pump 2 with water from Pond South?

1. To stop irrigation just for a while at a particular outlet tap, you merely need to turn off that open outlet tap.
2. To finish irrigation for the day, you first need to turn off all outlet taps along the Main Lines E, C, and W, then turn off the main in-line taps for all three Main Lines E, C, and W at Pump 2, and turn off the in-line tap of the inflow pipe from Pond South.
3. Pump 2 should have stopped working (after a few seconds).
4. Thereafter, switch off Pump 2 (NEVER the other way round: switching off the pump and then turning off taps).

How to let the water flow from the deep well into Pond South?

• Be aware that one of the two in-line taps of the outflow pipes from the deep well pipe must ALWAYS be kept open, meaning water can potentially flow through that in-line tap. NEVER CLOSE BOTH IN-LINE TAPS! If it happens that both in-line taps are closed while the submersible pump is switched on, extreme damage can be the result. Such damage can be the overheating of the submersible pump, followed by the burning and melting of its internal wiring. Thus, the PVC pipes together with the submersible pump have to be removed by pulling up step by step, and the pump replaced with a new one. Costs will be around 50,000 Baht. Even more severe damage can occur when the PVC pipe that leads down to the submersible pump bursts from water pressure. Then it might be impossible to remove the pipes from the borehole, and a new bore next to the existing one must be drilled. Costs may reach 400,000 Baht.

1. Check if the in-line tap of the deep well pipe towards Pond South is open.
2. If it is closed, open it and then close the in-line tap of the outflow pipe towards Pond East.
3. Thereafter, switch on the submersible pump, and, after a few seconds' delay, water from the deep well will flow into Pond South.
4. When this pond has reached the higher water level wanted, switch off the submersible pump, but DON'T TURN OFF THE IN-LINE TAP OF THE OUTFLOW PIPE.

Deep well

Deep well:
In-line tap (open) of the outflow pipe to Pond East (left).
In-line tap (close) of the outflow pipe to Pond South (right)

Pump hut with Pump 1 (P1)

Pump hut with Pump 1 (P1), from left to right:
Pump 1, showing outflow pipe with main in-line tap on the left and inflow pipe on the right;
outflow pipe, connecting to 5 underground main lines E, C, W, and S, each with an in-line tap, and with an additional in-line tap that connects to village tap water;
a second outflow pipe of the pump, with an outlet tap but not connected to an underground line;
the switch for Pump 1

Pump hut with Pump 2 (P2)

Pump hut with Pump 2 (P2), from left to right:
inflow pipe from Pond S and Pond E, each with an in-line tap
 (the left tap is open, the right tap is closed);
outflow pipe, with in-line tap, connecting to the underground main line E;
outflow pipes, each with an in-line tap, connecting to the underground main lines W and C;
switches are in the right gray box that can be opened: the left switch is for the submersible pump, the right switch is for Pump 2

An alternative operation mode of irrigation is by using Pump 1 with water only from Pond South. The starting and finishing irrigation of this mode is somewhat different from Pump 2. The difference in elevation between the water level in Pond South and Pump 1 is 1–2 m greater than that for Pump 2. For this reason, Pump 1 has a better suction capacity than Pump 2. Furthermore, to ensure smooth operation of Pump 1 (without constant automatic switching on and off), a greater discharge capacity is required than for Pump 2. To start Pump 1 for irrigation, several outlet taps (3 or more) from two main lines (e.g., West and South simultaneously) should be opened first. Only then should the corresponding main in-line taps on these main lines be opened. The pump will then start immediately. To stop the operation, first close the main in-line taps, then the outlet taps.