Shallow Buried Pipelines for Summer Pasture Livestock Watering

Author(s):Reynold Woelcke, Peace River District Office, Peace River, AB

If pasture land is adjacent to a farmstead then an alternative to constructing numerous pasture dugouts for summer pasture livestock watering needs is to install a shallow buried pipeline from the farmstead water source out to the pastures. When several pasture quarter sections are in an adjoining block the pipeline can extend from one quarter section to the next. With the availability of electric power from a power grid at the farmstead and by not burying the pipe more than 12 inches, pipelines that are several miles long are both practical and economical.

The advantages of the shallow buried pipeline are:

The cost of the pipeline is less than one or more pasture dugouts with remote watering systems. The cost per foot of the polyethylene pipe can decrease significantly as larger amounts are purchased.

A pipeline from a farmstead water source, whether a well or dugout, generally has water of better quality for livestock watering than a pasture dugout. Higher quality water consumption by livestock is believed to result in improved rates of gain. The farmstead water source is also generally better maintained and tends not to degrade in quality as quickly as a pasture dugout.

A shallow buried pipeline is a very flexible watering system, allowing water to be brought to practically any place in a pasture. A pipeline through the middle of the pasture allows for the ability to cross-fence the pastures because multiple outlets with shut-off valves can be inserted in the pipeline as desired. This increased cross fencing leads to shorter duration rotation grazing, resulting in better pasture health and increased pasture carrying capacity.

A pressurized pipeline is simple to install and operate.

A well or a larger farmstead dugout tends to physically degrade slower over time than pasture dugouts.

If during a drought the pasture water supply has dwindled, and the farm supply is secure (i.e. deep well or large dugout) then the water can be brought to the pasture relatively quickly.

A meter can easily be used to determine the livestock's water consumption rate. This is useful to indicate potential livestock health problems before they are visually apparent.

Some kinds of medication can be administered through the water.

Considerations

1. If the electrical power supply is likely to be interrupted for more than six hours in a day a back up water source or electrical power supply is required.
2. A non-functioning float valve at the stock tanks. The solution is to make sure that the float valve is securely protected from the livestock, and not to use at freeze after in the autumn.
3. In autumn before freeze up, the pipeline should have as much water removed as is easily done.
4. Having a backup water source such as an old water hauling truck, existing dugout, stream, or water pumped to a reservoir is also a solution if the water pipeline system is temporarily not functioning.

Design

When designing a pasture pipe system there are five criteria; (1) total cost, (2) the pressure limit of the pipe (usually set at 75 psi), (3) pumping time required to meet the livestock water needs, (4) the topography over which the pipe is laid, (5) the pump used.

Cost

The cost becomes a limiting factor when the pastures are not adjacent to each other, and if there are significant distances between pastures or between the pasture and the water and electrical power source. Also having to go through a road where a culvert does not exist adds significant cost to a project.

Pipe

The water pressure in the pipe must not exceed the pipe design pressure. When water is not flowing in the pipe the maximum pressure in the pipe is the pressure at the pump plus pressure resulting from any part of the pipeline being lower than the pump. For every 2.31 ft that the pipeline is lower than the pump add 1 psi to the maximum pressure in the pipeline.

The pressure rating of low density black polyethylene pipe relative to what it can actually withstand depends on whether it has a CSA approval rating or if it is non-CSA approved pipe. The non-CSA approved pipe often can be purchased from the same manufacturer either as a thick walled or thin walled pipe. It is important to know which is being purchased since the thinner walled pipe kinks much easier and has about half of the actual maximum pressure capability than the thick walled non-CSA approved pipe. The thick walled non-CSA approved pipe has very similar characteristics to the CSA approved pipe but has not undergone all the rigorous standards and testing that the CSA approved pipe must undergo. Thick walled non-CSA approved pipe is likely a better choice for this type of pipeline since;

1. it is significantly cheaper than CSA approved pipe but with similar strength,
2. the pipe is not used for human drinking water,
3. if it were to fail, the failure site would easily be found and the pipe repaired.

The temperature of the pipe has a significant affect on how much pressure that it can withstand. The higher the temperature, the lower the pressure that the pipe can withstand. For example CSA approved 75 psi series pipe at 23 C has a four fold burst pressure safety factor, i.e. is designed to fail at 300 psi; however, the same pipe at 60 C will fail at 45 psi.

The weight of the pipe /unit length of pipe can be used to distinguish the thicker walled pipe from the thinner walled pipe. The following are their typical specific weights:

Livestock Water Needs

The water flow rate must be sufficient to pump the required amount of water to the livestock during a 18 hour period (i.e., number of hours they are actively drinking). If there is insufficient flow in the pipeline, the solution is: (1) to use a larger diameter pipe, or (2) to use a pipe and/or pump with a higher maximum pressure rating. Although each situation is unique, in general 1" diameter pipe is sufficient to water up to 200 mature cattle; 1.25" diameter pipe may be needed for larger numbers of cattle.

Pipeline Burial

Unless the pipe is under shade, it should be buried to keep the water in the pipe from heating up as a result of direct sunlight (hotter water is less palatable to the livestock) and a hotter pipe has lower maximum pressure rating. Burying the pipe 6 to 12 inches is sufficient unless the land is to be cultivated in the future; if so, it should be buried 18 inches deep, though in many situations a 5 ft. wide uncultivated strip left over the pipeline is a practical alternative. The deeper that a pipeline is buried, the longer it can be used in late autumn. If not completely drained; however, the pipeline will stay frozen longer in spring and delay its use.

To bury the pipe economically, a deep plow can be used. A trenching plow built specifically for this use can be borrowed from Alberta Agriculture out of Fairview ( Contact Stephen Madden at 835-2291 ). This plow requires about a 50 hp tractor with a 3 point hitch. It can plow in a half mile of pipe in about 30 minutes.

Even though the pipe has some UV light inhibitors, it will become brittle and lose its strength quicker if it is left in the sun as opposed to being put underground. Burial also protects the pipe from damage from animals such as coyotes chewing on it.

Float Valve and Stock Tank

At the stock tanks a float valve with an opening at least ½ inch in diameter should be used in order to minimize excess pressure loss at the outlet. This may be as simple as a homemade strap hinge valve, a Gallagher float valve, a Hudson float valve, or a Honeywell Braukmann model VF270 float valve. The valve should be protected from the livestock.

A water trough made of plastic is useful since they are light and are resistant to damage when moved from one paddock to another. If this watering system is used in combination with short duration rotational grazing which in turn results in smaller pastures, the stock tanks do not need to be very large (300 gallons or less) since cattle will water individually or in small groups rather than large herds.

If livestock need to travel longer distances to water and therefore water as a herd then larger stock tanks are needed. In extreme cases where the water flows in the pipe most of a 24 hour period then the stock tank should hold up to half of the daily livestock watering requirement.

Water Hammer

ater hammer is not generally a concern in the design of this kind of pipeline for several reasons. The pipeline being long and made from low density polyethylene pipe is elastic enough to absorb the shock wave if it where to occur. The float valve used at the stock tank closes relatively slowly. Water velocities in pipelines longer than ½ mile are generally relatively slow (less than 5 ft/sec).

Before Freeze-up

Before freeze-up in the fall, remove as much water in the pipeline as is practical. Any sloping pipe should have valves installed at low points to be used as drains in the fall. Pipes installed on flatter land should have compressed air used to push as much water as is easily done. When using compressed air to blow out the water, high air flow rate ( i.e. cfm ) is needed rather than high pressure. One farmer has used the exhaust from an 8 cylinder truck motor as a mobile blower; estimated to produce about 45 cfm@ 3000 rpm and zero pressure. If used, rinsing the pipe in the spring before using it is advised.

Black polyethylene pipe is able to withstand freezing with some water remaining in the pipe. If water remains in the pipe at freeze-up, it is very important that the water pressure be removed in the pipe before the water is allowed to freezing in the pipe. The risk in allowing the pipe to freeze with it completely full of water is that if uneven freezing occurs; where the water on the ends freezes before the water in the middle, then the pipe in the middle will be forced to stretch beyond its elastic limit, will weaken and may break.

Rigid parts such as valves and sleeved pipe connections are susceptible to damage from ice formation. The connection sleeves should be made of galvanized steel. Remove all valves and store in a warm place before freeze-up. Care should be taken that mice do not enter the pipe while they are open.

Pump Considerations

The more often a pump turns off and on, the sooner it will wear out. So in setting up the pump for a pasture watering system the objective is to minimize the number of times that the pump cycles on and off, preferably having the pump stay on for more than three minutes per cycle. There are three ways of doing this: (1)adjusting the pressure settings on the pressure switch controlling the pump, (2) add a larger pressure tank (a hydro-pneumatic pressure tank ) to the system, (3) buy a separate pump whose pump characteristics best match the pipe system.

Ideally, once the float valve opens at the stock tank (e.g., when the tank is half empty) the pump should run continuously until the stock tank is full. In order for this to occur a steady state must be obtained, where the rate at which water is pumped into the pressure tank equals the rate the water flows out of the tank and to the stock tank, at a pressure below the shut-off pressure. The longer the pipeline is and/or the smaller the pipe diameter, the more pressure loss occurs in the pipe for a specific water flow rate, or the lower the water flow rate in the pipeline for a specific pressure.

If the pump is overpowered for the pipeline system then this equilibrium cannot be achieved and the pump will cycle on and off. Adding a large hydro-pneumatic pressure tank near the pump will reduce the frequency of pump on/off cycling. Doubling the volume of a hydro-pneumatic tank reduces the pump on/off cycles by half. If more tank volume is desired, then adding a tank instead of replacing the exiting tank is beneficial.

Shallow well jet pumps are commonly used to draw water to a house from a dugout, and are well suited for that application. However, they are relatively inefficient pumps, so if many livestock are being given water, then a different overall pumping system or a separate livestock pump may be worth getting (e.g., a pump setup with low or zero suction pressure on the inlet side of the pump).

In some situations adding a livestock watering pipeline to a household pump system may cause inconvenience in the house where the house water pressure becomes too low when water is being pumped to the livestock. This can occur if large numbers of livestock are being watered and the pipeline to the stock tank does not produce enough back pressure. This is generally the case for shorter and larger diameter pipelines. There are several solutions to this: (1) the simplest solution is to restrict the flow to the stock tank with a partially closed valve, (2) another solution is to use a smaller diameter pipe to the stock tank, (3) to install a separate hydro-pneumatic tank, pressure switch, solenoid valve and check valve to the system ( see figure. 1 ), and (4) to install a separate water pump from the water source to the stock tanks.

Generally, for watering a large amount of livestock, the following is recommended: If pumping water from a dugout a separate pump should be installed where the pump is relatively close to the dugout in both elevation and distance to minimize the negative pressure on the pump's suction side. Where the water is being pumped from a well, using a solenoid valve ( see figure 1 ) is a practical alternative to developing a separate new well for the livestock.

Tables

• Download tables (Excel spreadsheet)

Tables 2 and 3 give estimated design values of a pipeline scenario in which 100 cattle are being watered for six months from a pipeline which is on level ground. The only difference between table 2 and table 3 is that in table 2 the pressure at the start of the pipeline is set to 45 psi and in table 3 it is set to 75 psi. Each table has common input values except for pipeline length which varies from one column to the next. Each column in the tables gives estimated water flow rates and other calculated values associated with that pipeline length in the same column.

Note how the "Minimum Motor Power" requirement is reduced as the pipeline lengthens. The power required to pump water to stock tanks is only proportional to the pressure and the water flow rate. As a pipe becomes longer, it adds resistance to the water flow, resulting in less flow, and hence less power is needed to pump the water. The annual power cost is essentially proportional to the amount of water pumped and the pressure that it is pumped at. It is not affected by the rate at which water is pumped.

These Tables give a feel for what can be expected from a pipeline. A more accurate estimation of the performance of a pipeline would include a specific pump's performance data, pump pressure switch settings and the size of the hydro-pneumatic tank associated to the pipeline system.

PFRA can assist you in designing a summer pasture livestock watering pipeline for more specific situations. For more information, please contact Reynold Woelcke at (780) 624-7666 or your nearest PFRA office.