Identification of Different Irrigation Valves: A Comprehensive Guide

Irrigation systems play a vital role in maintaining healthy lawns and gardens. To ensure efficient water distribution, it’s crucial to understand the various types of irrigation valves and their specific purposes. In this article, we’ll explore the different types of irrigation valves and provide insights into key terms associated with them.

Lawn Irrigation Systems: Inline or Anti-Siphon?

Inline systems feature valves that are aligned with the underground supply pipe or tubing. These valves control or block flow through a mechanical obstruction that can be activated manually or electronically. The advantage of inline valves is their ability to be installed inconspicuously anywhere in the landscape without causing visual disruptions.

Anti-siphon systems, on the other hand, have valves positioned above ground. These valves sit on a supply line that loops up from the ground at a discreet location. Anti-siphon valves employ an air gap mechanism to prevent backflow when a backflow condition occurs. This above-grade installation eliminates the risk of submersion and provides convenient access for maintenance and repairs.

Categorizing Lawn Sprinkler System Valves by Use

1. Isolation Valve: This valve serves to isolate the irrigation system from the main water supply when closed. Opening this valve allows water from the main supply line to enter the irrigation system, while closing it is necessary for winterization. In an inline irrigation system, the isolation valve is typically located underground near the meter. In an above-ground system, it can be found indoors or above ground near the point where the main water line exits a structure, such as a basement or garage.

2. Backflow Prevention Device: Considered the most critical component for health and safety purposes, this valve or series of valves prevents water from flowing back into the potable water system. It ensures that water entering the irrigation system stays isolated. The backflow prevention device should always be downstream from the isolation valve, regardless of whether it is above or below ground.

3. Automatic Zone Control Valve: Connected to a timer/controller, this valve regulates the flow of water to a specific zone of sprinkler heads and drip emitters. In inline systems, zone control valves are installed in an underground valve box. For anti-siphon systems, they are discreetly installed above ground.

4. Lateral Line Drain Valve: This simple valve is strategically placed at the downstream ends and low spots in the system to drain lateral lines after each use, preventing water from becoming stagnant and causing damage.

Identifying Lawn Sprinkler System Valves

Valves are identified based on their size, inlet connection type, outlet connection type (if different), and mechanism. For example, a valve could be labeled as “1″ NPT (National Pipe Thread) ball valve.”

Mechanism Types

1. Ball Valve: This type of valve opens when a sphere with a hole in the center aligns with the inlet, allowing water to flow. It closes when the ball is turned using a quarter-turn handle, positioning the hole perpendicular to the inlet.

2. Gate Valve: A gate valve is open when a disk-shaped “gate” is lifted out of the water pathway. Rotating the handle clockwise lowers the gate into the pathway, effectively closing the valve.

3. Check Valve: Equipped with a disk positioned at a forty-five-degree angle to horizontal, a check valve allows water to flow in the normal direction by pushing the disk upward. In the event of backflow, the disk is pushed down against the seat, stopping the flow.

4. Automatic Valve: Powered by a solenoid, this valve automatically opens at programmed times and intervals set by the system controller.

Connection Types in Inline Underground Irrigation System Valves

1. FPT (Female Threaded): Also known as FIP, female threaded connections are commonly found in inline underground irrigation system valves.

2. MPT (Male Threaded): Sometimes called MIP, these male threaded connections are also prevalent in inline underground irrigation system valves.

3. NPT (National Pipe Thread): Another type of threaded connection, NPT is commonly used in inline underground irrigation systems.

4. S (or Slip): This straight, smooth female connector is designed to receive pipe or “street” (male) fittings. Metal slip connections are soldered or brazed, while plastic connections are glued.

5. Barb: This male connector with barbs is inserted into pipe or tubing and secured with stainless steel crimp clamps. However, barb connections are not used for backflow prevention devices.

6. Union: Installed in pairs, these two-piece threaded connectors allow for easy disconnection of the connected parts. When installing unions, the inlet and outlet of each union are glued to the pipe or valve. Tightening the nut completes the connection by securing the threaded portion of one piece to the other.

Miscellaneous Terms

1. PVC (Schedule-40 PVC Pipe): Often used for supply lines downstream of zone control valves, PVC refers to Schedule-40 PVC pipe. This type of pipe is commonly used for valve installations explained in this article.

2. Solenoid: An electromagnetic device consisting of wire wrapped around a core, a solenoid produces a magnetic field when activated. In irrigation applications, it opens automatic lawn sprinkler system valves when prompted by the system controller.

3. Glue (Solvent Cement): Despite the common use of the term “glue,” solvent cement is the proper name for the adhesive used in plastic joints. Solvent cement chemically reacts with plastic, causing it to soften or melt slightly, creating a secure connection between hub and pipe.

4. Thread Tape: A thin, non-adhesive tape used for making threaded connections, thread tape provides a waterproof seal for tapered-thread joints when applied correctly. The Teflon material reduces friction, allowing for tight threading and expansion to fill gaps.

5. Thread Sealant Compound: Easier to apply than thread tape, thread sealant compound is impregnated with Teflon for effective friction reduction. It works well with brass, copper, and PVC materials, but any excess compound should be manually removed to avoid clogging valves. Note that some plastic types may be damaged by the solvents in the compound, so thread tape should be used with those materials.

By understanding the different types of irrigation valves and their specific functions, you’ll be better equipped to plan and maintain an efficient irrigation system for your lawn or garden. Whether you choose inline or anti-siphon systems, ensuring proper valve identification and connection types is essential for optimal performance.