Creating design/builds for commercial irrigation projects can feel like walking a tight rope. You need to find balance between overdesigning, which has the potential to price you out of the market, and under-designing where you may not meet a client’s needs or expectations.
When you find the right balance, the opportunity is tremendous and will allow you to outperform and outsell the competition. Better yet, having the right balance doesn’t mean you have to choose the least expensive products to stay competitive either. The opportunity is in how you help your client approach total cost of ownership for a project. So, what do I mean by that?
The total cost of ownership includes hard costs such as installation, maintenance, repairs, water, power and landscape replacement, and maintenance costs. But there are nontangible costs that are often just as critical to the client such as playability of sports fields, usability of open park spaces, and curb appeal to renters/commercial tenants/users.
Offering value-added solutions can help lower the total cost of ownership for your client. Yes, there may be a higher upfront investment cost but things like less maintenance, remote monitoring to fix issues before they become a problem, increased usable lifespan (doubling to tripling it), and the functionality to add service contracts help lower the total cost of ownership for a client. A brief explanation in your proposal of each value-added option could separate you from the competition and help create a consultative relationship with the decision makers.
Below are four examples of value-added options to help you find the right balance with your commercial irrigation projects and help you stand out from your competition:
1. Center-Feed vs End-Feed
Think of a row of ten heads fed from a valve at one end. This is referred to as end-fed. Since dynamic pressure is always greater closer to the valve, the first head will see the most pressure. Due to friction loss through pipe, the tenth head will see the least pressure, assuming no downward slope.
For best performance, dynamic pressure at the last head of any zone should be within 5 – 10% of the first head. This can be difficult to achieve in end-fed zones. Operators will often increase run time to make the furthest area of the zone as lush and green as the area closest to the valve. This however results in wasted water, need to water outside of acceptable times, overwatered plant material, saturated/unhealthy turf—and ultimately wasted money.
Now, think of those same ten heads being fed by the valve placed between the fifth and sixth heads. There will be five heads on each side. This is referred to as center-fed. When the zone operates, the dynamic pressure at the first two heads on each side of the valve will be the same, as will the second two heads, and so on. Essentially, there will be only five different dynamic pressure readings at all ten heads rather than ten different readings like with end-fed.
Center-fed zones make it easier to keep dynamic pressure throughout the zone from varying by more than 5 – 10%. Center-fed zones may require more lateral pipe, which means a higher initial cost but ultimately the long-term results will speak for themselves: water savings, labor savings, less likely to need to treat unhealthy turf or replace plant material—and ultimately a lower total cost of ownership for your client and less headaches all around.
2. Use Pressure Regulation
How to Calculate the “Sweet Spot”
The manufacturer’s spray and rotor performance charts are based on dynamic pressure at the base of the head and show the resulting flow in gallons per minute and radius of throw. All nozzles available for the head are shown in the charts. For each nozzle, 5 or 6 dynamic pressure points are usually given. The “sweet spot” of best performance for that product is usually in the middle of the points shown. I always recommend to design at the “sweet spot.”
For your system to work correctly when installed, it is critical that the heads operate at the dynamic pressure selected in your design. If pressure is higher than the design point, too much water will flow. This could result in an inefficient spray pattern that is more susceptible to wind drift or the radius of throw could be reduced, resulting in dry areas. Operators will often increase run time, attempting to eliminate the dry areas but they actually just end up wasting water and money.
Eliminate Excess Pressure & Inefficiencies
Pressure regulation can easily eliminate the consequences of excess pressure. You should always perform friction loss calculations on your design—it is better to know before installation that regulation will be necessary than to have to add it later. There are several pressure regulation choices: an in-line regulator at the point of connection, an add-on regulator at the master and/or zone valves, and built-in regulation at the spray or rotor.
Generally, regulation at the head is best because it is closest to the nozzle. Virtually all manufacturers have optional regulation built into spray and rotor bodies designed to reduce excess pressure to the sweet spot. Since it is built into the body, it cannot be added later without replacing the existing body. This is never a good choice; plan carefully in advance so it will not be necessary. Also note, that several states are now requiring pressure regulating heads, I anticipate that we will see this trend continue and more regulations added.
Manufacturers offer optional add-on regulation for their commercial valves. Read the specifications carefully – they work only within certain flow and pressure ranges. They often require higher flow than the valve is capable of managing without the added regulator.
In-line regulators at the point of connection are typically made of bronze and rated for very high pressure – often up to 300 PSI. Common regulators can be used to reduce pressure by 20 to 75 PSI.
In cases of very high system pressure, it is often necessary to use two forms of regulation: at the point of connection and at the valve or head. Regulation at the point of connection lowers system pressure to a range that the regulator at the valve or in the head can manage.
3. Flow Sensors
Flow sensors should be used when clients need to report water usage or if they wish to track usage for their own purposes. Several types of sensors are available: impeller, magnetic and ultrasonic. Care should be taken in selecting the right type and size.
For most relatively simple commercial applications, an impeller meter is fine and is usually the most cost effective. Different sensors provide different outputs to the controller. It is important to know the differences and the types of inputs your controller of choice can accept. If you are not sure, let us advise you. We can also advise you if the controller and controller software can provide data in the format that meets your client’s needs.
Depending on hydraulic design, flow sensing can become complex. Commercial controllers may manage multiple mainlines, there may be multiple controllers managing one mainline or multiple points of connection into one mainline. In very large mainlines, a “bypass” sensor in a small section of main can pick up lower flow rates beyond the capability of the large sensor.
4. Isolation Valves
Isolation valves can be on the mainline and before each zone valve. These can be either gate or ball valves and brass or plastic. Isolation valves are helpful on long mains, looped mains, and those with various submains. Think in terms of repairing the main in case of a leak or break. Instead of shutting down the entire system, it is always better to isolate just a section for repairs while letting the rest continue to operate.
Isolation valves in front of zone valves are helpful when the valve needs to be opened for repair. This avoids the need to shut down and drain the entire main, or a section of the main to do a simple valve repair. I once saw a large system take 24 hours to drain before a damaged valve diaphragm could be replaced. The replacement took 15 minutes, but an entire irrigation cycle was lost.
At Central Turf, we are experienced in commercial design and projects. Ask us your toughest questions; we are here to assist and help make you more efficient, competitive, and profitable in your commercial work.
About Dave Shane
Dave has more than three decades of experience in the irrigation industry in both distribution and manufacturing roles. He specializing in commercial project solutions with an emphasis on controls to meet complex requirements. He is an excellent resource for any technical questions about irrigation systems and finding the right solutions for efficient irrigation systems.