Go back to Part I - MarketGro 1500 System - Overview

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Main Valve Assembly

First we extend the 1-1/2" Series 75 supply tubing from the source pump or standpipe to the edge of the crop area at full pressure. That way the water pressure at the source is maintained as long as possible and will help overcome friction losses. We can leave the entire system above ground so that it is easy to monitor and maintain.

If you are using municipal water or if there is a possibility of contamination by syphon or backflow into the water source, you should install an anti-syphon valve or anti-backflow valve or both. Qualified plumbers can supply the parts and install to code requirements.

At the edge of the crop area, we will add a 1-1/2" ball or gate valve which is available from any local plumbing shop. The valve will serve to shut off water pressure to all components downstream when maintenance is required. Next we add a Tee (FB25) and a Air Release/ Vacuum relief valve (OE17). The relief valve will allow air trapped in the system to escape at startup so that air is not trapped in the filter or pressure regulator. When the system is shut down, it allows air to flow into the system to prevent damage from a vacuum.

Filter Assembly

After the Air Release valve, we install a disc filter with 1-1/2" pipe threads, such as our FLR7 that has a capacity of up to 35 gallons per minute ( 2100 gallons per hour).

Immediately after the filter, we add a pressure regulator with 1-1/2" pipe threads. Our PR7 will work well and has a flow capacity up to 35 gallons per minute (2100 gallons per hour) and a pressure rating of 15 psi. (Other pressures are available)

Row Assembly

After the pressure regulator comes the Row Assembly for our system. The Row Assembly (header) delivers water to the start of each row. You have a choice. To make the Row Assembly you can either use the same 1-1/2" heavywall supply tubing that was employed as the supply line. Or we can replace that 1-1/2" tubing with 1-1/2" Polynet flat tubing (T6600). Polynet flat tubing has the advantage of being inexpensive, shippable, lightweight and easy to roll up to move from one field location to another. The wall thickness of Polynet is also thin enough to use a punch for barbed fittings. We can use Polynet only for the Row Assembly since the maximum working pressure is 21 psi, not sufficient for use as the main supply tubing from the well/source. Our Row Assembly photo shows 1-1/2" Series 75 PE tubing.

Next we install a tee insert fitting (FB24) at each row. Screw clamps (OE21) are necessary at each tee and silicon tape (OE16) should be wrapped three wraps around all pipe threads to seal the threads. Then we install an adaptor (FB19T or FB20) to go from the FB24 fitting to the dripline or tubing you wish to use in each row. Lastly, add an end stop (FB18T or OE7) at the end of each row of tubing, depending on the type of dripline or tubing you choose. Figure 7 shows an optional ball valve that can be used to shut off each row if needed.

Dripline Options

Thinwall dripline is much less expensive but will have approximately half the service life of heavywall dripline. Other considerations include the quality and cleanliness of your water source. Heavywall dripline is often better for a long-term installation with excellent water. Thinwall is best for temporary installations or if water quality is less. Thinwall is lighter and easier to move out of the way for field cultivation but heavywall will take more abuse.

End Assembly

To close off the end of the Row Assembly (header), we could simply add an end cap. But trapped air may create problems so it's best to add a Tee fitting (FB25) and another Air Release/ Vacuum Relief Valve (OE17) to the End Assembly just before the end of the header. (See Figures 8 and 9) The flush valve shown in Figure 9 is another option for flush-cleaning the header.

Air in the System

Small bubbles of air can accumulate in a drip system. They can come from a leaky pump, suction hose or fitting. When enough air is trapped in the tubing or in a filter or regulator, the flow of water can be blocked and reduced. Test by allowing air to escape.

Figure 7 - Row Assembly with ball valve to control each row - Click to Zoom

Air accumulates at the high points of a system. Add Air Release/Vacuum Relief Valves (OE17) whenever air collects in the system and blocks the flow of water. The Air Release valve allows air to escape until a preset pressure is reached, then the valve closes.

When a drip irrigation system is shut down, water will flow out the drippers and may form a partial vacuum within portions of the tubing. The vacuum may be strong enough to collapse tubing. An Air Release/Vacuum Relief Valve (OE17) will allow air to flow into the tubing to relieve the vacuum. As with air release, high points in the system are the best locations to relieve a vacuum.

Flushing Header

One option that is recommended is a flushing header. Instead of simply ending dripline in each row with an end stop, all dripline ends are joined to a length of 1-1/2" tubing in the same way that the dripline is joined to the Row Assembly. The 1-1/2" tubing Flushing Header is capped at both ends and serves two purposes. To flush the rows, simply open one end of the flushing header to flush all rows at the same time. Even more important, a flushing header permits water to flow both ways in the rows. This turbulence keeps sediment moving until it can flush out of the dripline.

A flushing header requires 30% more flow than normal and an increase of 6 to 8 psi. It may be necessary to divide the system into two zones to provide the extra flow. The source water needs to be bypassed through a regulator with a higher pressure rating for flushing. Otherwise, flush each row individually.

Maintenance

Drain all water from all tubing and parts in the fall before winter to avoid damage from freezing water.

Flush all tubing in the spring when the system is first started up and again in the fall when the system is shut down. Flush regularly if water quality is not the best. Remove end stops and let water flow through each header and row one at a time until the water runs clean. Re-install the end stop and move on the next length of tubing.

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Figure 10 - Optional Flushing Header installed at end of all rows