Fix Uneven Watering Before You Try Crop Steering

Uneven watering wrecks consistency. In this episode, Omar from Rivulis joins Tyler from Front Row Ag to break down the most common mistakes in irrigation system design, from pressure regulation to clogged emitters, and how to fix them with real-world setups and smarter components.
Topics: 

• The truth about pressure vs. flow
• Why your “perfect” crop steering protocol fails if irrigation is off
• What dripper pressure specs actually mean
• Best practices for line cleaning and dripper maintenance
• Whether automatic flush valves are worth the investment

Perfect for: growers, irrigation techs, facility managers, and anyone building or troubleshooting fertigation/irrigation systems in commercial agriculture.
Subscribe to Front Row Ag on YouTube for more grow system science & expert insight.
Chapters:
00:00 – Why Uneven Watering Happens in New Facilities
01:30 – Pressure ≠ Flow: What Every Grower Gets Wrong
03:00 – Common Mistakes: Leader Pumps Without Pressure Regs
04:05 – You Can’t Crop Steer if Your Irrigation is Garbage
05:30 – How to Calculate Flow, PSI, and Zone Design Like a Pro
06:45 – Why Emitters Matter & How to Pick the Right One
08:00 – How Often Should You Replace Drippers?
09:45 – Fixing Filters, Clogged Emitters & Cleaning Mistakes
13:15 – Correct Way to Clean Irrigation Lines (2-Part Flush Method)
20:00 – Understanding Opening Pressure vs Sealing Pressure
24:30 – Sizing Pumps, Choosing Tubing, and Avoiding Supply Mistakes 32:00 – Automatic Flush Valves: Worth It or Waste?

In new facilities, one of the most common mistakes is installing PVC piping first—whether schedule 40 or schedule 80—before planning the plant count and irrigation needs. Without designing the correct flow rates for the actual application, systems often fail to deliver proper performance once they’re turned on.

As irrigation manufacturers, we’re responsible for delivering the correct amount of water and nutrients to plants. Even though irrigation components may not be the most expensive part of a facility, they’re critical and carry the most liability when it comes to system performance.

A frequent issue is choosing incorrect components. For example, if you use a Leader pump without any pressure regulation at the bench, you’ll get uneven distribution. Drippers are designed to operate within specific pressure ranges, and exceeding those limits doesn’t make them “pop off,” but it does cause friction losses and uneven delivery.

It’s important to understand that pressure and flow are not the same thing. Many people confuse the two. Leader and DAB pumps, for instance, operate differently, and knowing how each works is essential for setting up the right pressure and flow for your benches.

Drippers themselves are designed with specific ranges. Some open at 9.5 psi, others at 17 psi, and both typically work up to 50 psi. The key is to keep them operating within their intended range to maintain consistency. Without regulation, you end up with “tallies and shorties”—plants at different points in the row receiving different volumes. Even with top-quality emitters, incorrect setup creates variability.

Adding simple components like regulators and gauges can solve many problems and make troubleshooting much easier. Without them, diagnosing uneven irrigation is possible but slower.

From a crop steering perspective, uniform delivery is non-negotiable. Even the best steering protocols are useless if plants aren’t getting equal volumes. Planning early with basic math—counting emitters per plant, calculating flow per zone, matching it against the pump curve—prevents most issues. Unfortunately, many facilities skip this step.

Rivulis Supertif emitters and similar components offer features like pressure compensation, minimum opening pressures, and non-drain options that can be valuable depending on the setup. But again, the priority is ensuring every plant gets the intended volume during each irrigation event.

On the fertigation side, clogged emitters are one of the most common complaints. Problems often come from poor pH adjustment, improper mixing, or neglecting line maintenance. Proper filtration and regular cleaning are critical. Whether using screen or disc filters, the important factor is monitoring pressure differential across the filter—typically a 3–7 psi drop indicates it’s time to clean.

For post-harvest line maintenance, the best practice is a two-step cleaning process. First, fill the lines with an acid or cleaning solution and let it sit with flush valves open, ensuring biofilm and debris are cleared from tubing. After flushing the lines, a second pass can run cleaning or sanitizing solution through the emitters themselves for direct service. Always finish with clean water before replanting.

Emitter design plays a role here as well. Pressure-compensated non-drain emitters (PCND) retain water in the lines, preventing air pockets and ensuring more consistent starts. They have specific opening and sealing pressures that dictate when they activate and shut off. Using higher opening pressure emitters can also improve line maintenance procedures.

Ultimately, irrigation should be designed around flow rates, not just pressure. Pumps, fittings, tubing diameters, and layouts all affect hydraulic performance. For example, 17mm tubing may only handle 5 gallons per minute at proper velocity, while 18mm or larger diameters allow more. Closed-loop layouts with flush valves and pressure gauges at the ends of benches improve uniformity and make maintenance easier.

Automatic flush valves are another option. They release water briefly at the start of an irrigation cycle, clearing debris before resealing. While they add extra water use that must be accounted for, many growers find them beneficial, especially in large facilities.

With good line maintenance and filtration, emitters can last many years, though replacement every 6–12 months is often recommended for reliability. Like LED lights, emitters may keep “working” but won’t necessarily deliver the correct output forever, especially under heavy use and chemical exposure.

In summary:

• Design irrigation around flow rate, not just pressure.
• Size pumps, tubing, and emitters to match plant count and zone demand.
• Use regulators, gauges, and flush valves for consistency and troubleshooting.
• Maintain filters properly and clean lines in a two-step process.
• Consider emitter replacement as part of regular maintenance.

These steps ensure even delivery, prevent clogging, and keep fertigation systems reliable over multiple crop cycles.

Transcript:

One of the most common causes of uneven irrigation in a new facility actually begins during the design phase.

A lot of facilities install all of their PVC piping first and only later decide how many plants they'll have or how much water each irrigation zone will need.

That approach creates problems because the hydraulic system wasn't designed around the actual flow requirements of the crop.

As irrigation manufacturers, our responsibility is ultimately to deliver the correct amount of water and nutrients to every plant. Even if irrigation components aren't the most expensive part of a facility, they're one of the most critical because they're the final step before the solution reaches the crop.

Beyond pipe sizing, component selection is equally important.

For example, imagine an irrigation bench supplied by a pump but without any pressure regulation at the bench itself.

In that situation, it's very easy to end up with uneven water distribution.

Many growers think about pressure and flow as if they're the same thing, but they're not.

If there's one concept I hope everyone takes away from any irrigation discussion, it's this:

Pressure and flow are two completely different variables.

You need both to be correct.

Different pumps behave differently.

Some pumps allow much finer pressure control than others, so understanding the equipment you're using is just as important as selecting the right emitters.

The same principle applies to pressure-compensating drippers.

Different models operate within different pressure ranges.

For example, one emitter may begin operating at approximately 17 PSI, while another begins opening around 9.5 PSI. Both may function properly up to around 50 PSI, but understanding those operating ranges is essential when designing the irrigation system.

A real-world example illustrates the problem.

Imagine a facility with two irrigation benches supplied by a pump that has no pressure regulation at the bench.

When one irrigation zone turns on, the pressure reaching that bench might be 55 PSI.

That exceeds the recommended operating range for many emitters.

This doesn't necessarily mean the drippers will fail mechanically or blow off the tubing.

Instead, it means they may no longer deliver the precise amount of water they're designed to provide because they're operating outside their intended specifications.

The result is uneven irrigation.

You often see this expressed directly in the crop.

Plants closest to the water source become larger and more vigorous, while plants farther down the irrigation line remain noticeably smaller.

Growers sometimes blame genetics or environmental variation, when the real issue is simply inconsistent hydraulic performance.

Even the best irrigation components can't compensate for poor system design.

Proper pressure regulation, pressure gauges, and other relatively inexpensive hydraulic components often solve much larger problems.

Some people assume recommending those components is simply about selling additional equipment.

From my perspective, it's really about making the entire system easier to troubleshoot.

If pressure gauges and regulators are already installed, diagnosing irrigation issues becomes quick and straightforward.

Without them, you can still troubleshoot the system—it just takes considerably longer.

This matches what we see from the nutrition side as well.

Many growers want to jump directly into advanced irrigation strategies like crop steering.

But none of those strategies matter if every plant isn't receiving the same amount of water to begin with.

Even the best crop steering protocol falls apart if irrigation uniformity isn't there.

Before worrying about advanced irrigation scheduling, every facility should first verify that:

• Every plant has the same number of emitters.
• Every emitter has the same flow rate.
• Each irrigation zone is operating within the correct pressure range.
• The pump can deliver both the required flow and the required pressure simultaneously.

It's surprising how often facilities skip this planning process.

Ideally, before construction even begins, someone should calculate:

• The total number of plants.
• Emitters per plant.
• Flow rate per emitter.
• Total flow required for each irrigation zone.
• Whether the selected pump can deliver that flow at the desired operating pressure.

A relatively small amount of hydraulic planning prevents a tremendous number of irrigation problems later.

Good irrigation design is mostly good math.

When those calculations are done correctly from the beginning, everything else becomes much easier.

Hydraulics are the foundation of irrigation uniformity.

When a facility is experiencing uneven watering, one of the first questions to ask is whether the system is actually capable of delivering the required flow rate.

A common mistake occurs when a facility is originally designed around one emitter size and later changed.

For example, if the irrigation system was designed around lower-flow emitters and someone later switches to higher-flow emitters—or increases from two emitters per plant to four—the total water demand can increase dramatically.

Before making those changes, you need to verify that the existing pump and plumbing can still supply enough water to every irrigation zone.

Otherwise, you're asking the system to deliver more water than it was ever designed to provide.

When that happens, problems usually appear very quickly.

Within the first crop cycle you'll often notice uneven plant growth, and growers may assume individual emitters are clogged.

In reality, many of those emitters aren't clogged at all.

They're simply not receiving adequate flow because of hydraulic limitations elsewhere in the system.

That's why troubleshooting should always begin with the hydraulics before replacing irrigation components.

From the fertilizer side, we spend a lot of time helping growers troubleshoot clogged emitters as well.

We pay close attention to things like:

• Injection pH
• Concentrate compatibility
• High EC interactions
• Routine line maintenance
• Filter maintenance

Proper filtration is one of the most important preventative measures available.

Many growers ask whether they should use screen filters or disc filters.

The answer depends largely on the application.

Some systems perform better with disc filtration upstream, while others use screen filters closer to the irrigation benches.

Neither option is universally better.

What's much more important is knowing when the filter actually needs cleaning.

This is where pressure gauges become extremely valuable.

A filter should have one pressure gauge upstream and another downstream.

The upstream gauge measures the pressure entering the filter, while the downstream gauge measures pressure after the water passes through it.

As debris accumulates inside the filter, the pressure drop across the filter gradually increases.

Once the pressure differential reaches roughly 3 to 7 PSI, it's time to clean the filter.

Instead of opening filters every day to check whether they're dirty, simply monitor the pressure gauges.

Many facilities even mark the gauges with a red line so operators immediately know when service is required.

Pressure gauges aren't only useful at the filter.

Installing another pressure gauge at the end of each irrigation bench allows you to verify that the emitters are operating within their intended pressure range.

This makes troubleshooting much faster whenever irrigation problems occur.

Line cleaning is another area where mistakes are common.

Many facilities add a cleaning solution to the irrigation system, immediately push it through the emitters, allow it to sit, and then restart irrigation.

The problem is that emitters aren't designed to pass large amounts of loosened debris and biofilm.

A better approach is to clean the irrigation lines first while preventing the emitters from opening.

The process looks something like this:

1. Fill the irrigation lines with the cleaning solution while keeping the emitters closed whenever possible.
2. Allow the solution to remain in the lines for the appropriate contact time.
3. Open the flush valves and thoroughly flush the loosened biofilm and debris from the tubing.
4. Only after the irrigation lines have been cleaned should the cleaning solution be passed through the emitters themselves.
5. Finish by flushing the entire system with clean water before placing it back into service.

This two-step approach keeps dislodged debris from being forced directly through the emitters and greatly improves the effectiveness of post-harvest irrigation maintenance.

The discussion here is focused on post-harvest maintenance, after the crop has been removed from the room—not while plants are still actively growing.

Separating line cleaning from emitter cleaning helps preserve emitter performance while removing much more accumulated biofilm from the irrigation system as a whole.

Another important concept is understanding how pressure-compensating, non-draining emitters actually work.

These emitters contain a check valve that retains water inside the irrigation tubing after each irrigation event.

That serves two important purposes.

First, the emitter provides pressure compensation, meaning it delivers a consistent flow rate across a specified pressure range.

Second, because the tubing stays full of water after irrigation stops, every emitter begins flowing much more uniformly during the next irrigation event instead of having to refill empty tubing first.

These emitters have both an opening pressure and a closing (sealing) pressure.

For example, one emitter may begin flowing at approximately 9.5 PSI, while another may require around 17 PSI before it opens.

Once irrigation stops, the internal check valve seals at a much lower pressure, trapping water inside the tubing until the next irrigation cycle.

Higher opening-pressure emitters can also simplify maintenance because it's easier to keep them closed while performing certain cleaning procedures.

One thing many people focus on is pressure.

In reality, irrigation design should be driven primarily by flow rate.

Pressure is important, but flow determines how much water the system actually needs to deliver.

Everything should be sized around the required flow:

• Pump capacity
• Pipe diameter
• Tubing size
• Manifolds
• Fittings
• Emitters

Even something as simple as incorrect fittings between the storage tank and the pump can create hydraulic restrictions that affect the entire irrigation system.

Sometimes the irrigation layout throughout the room is perfectly designed, but the plumbing feeding the pump is undersized.

If the pump can't receive enough water—or can't move enough water into the manifold—every downstream component suffers.

Hydraulic problems often begin before water ever reaches the irrigation benches.

Air management is another commonly overlooked topic.

If a pump starts and the plumbing visibly shakes or vibrates, that's a sign something isn't right.

Air release and proper hydraulic design play an important role in overall system performance, yet they're rarely discussed.

One question growers often ask is how frequently emitters should be replaced.

With proper maintenance, many facilities successfully use the same emitters for five years or more.

Good maintenance can dramatically extend their service life.

That said, emitters shouldn't be viewed as permanent components.

Their job is simple but critical:

Deliver the correct amount of water and nutrients at exactly the right time.

Over years of operation they're exposed to acids, sanitizers, fertilizers, mineral deposits, and routine cleaning chemicals.

Eventually, replacement should be considered as part of normal preventative maintenance.

There's no universal replacement schedule.

Some facilities may choose every six months, others annually, while some may successfully operate much longer depending on maintenance practices and system performance.

The important point is to evaluate emitter performance rather than assuming they'll remain perfectly accurate forever.

If you begin noticing uneven irrigation, first verify the hydraulics, confirm proper maintenance has been performed, and measure actual emitter output before assuming individual emitters are at fault.

Another common design question involves the layout of irrigation tubing on each bench.

Many facilities run a single line with a flush valve at the end.

Personally, I prefer a closed-loop design with both a flush valve and a pressure gauge installed at the end of the loop.

The closed loop helps equalize pressure throughout the bench, while the flush valve makes maintenance easier and the pressure gauge provides immediate feedback about how the irrigation system is performing.

Tubing size also matters more than many people realize.

Different tubing diameters support very different flow rates.

Simply calling something "half-inch" or "three-quarter-inch" tubing isn't enough, because different manufacturers use different inside diameters with different hydraulic capacities.

Selecting the proper tubing size based on expected flow is another key part of achieving uniform irrigation.

When all of these pieces work together—proper hydraulic calculations, correct pump sizing, appropriate tubing, pressure monitoring, filtration, routine maintenance, and thoughtful system layout—you create an irrigation system capable of delivering truly uniform watering across the entire facility.

Automatic flush valves are another component that often generates questions.

In principle, they're a useful tool.

When irrigation begins, the flush valve opens briefly, allowing water to flush accumulated debris from the end of the irrigation line before sealing and allowing normal irrigation to continue.

The key consideration is that the flushed water still counts toward your total irrigation volume.

If each irrigation zone flushes a fraction of a gallon every time irrigation starts, and you're running many zones with high-frequency irrigation, those losses add up.

For example, if multiple zones each discharge a small amount of water at the beginning of every irrigation event, the total water and nutrient solution lost over the course of a day can become significant.

That doesn't necessarily make automatic flush valves a bad idea.

It simply means you need to account for that additional volume when calculating irrigation shot sizes and overall water use.

Many automatic flush valves also have adjustable settings depending on the flow rate through the irrigation zone.

For lower-flow benches, the lower flush setting is generally appropriate, while higher-flow benches may require a larger flush volume.

Table length also influences how much flushing is needed.

A 40-foot bench behaves differently than an 80- or 100-foot bench.

Even with automatic flush valves, most of the irrigation water remains inside the tubing after each irrigation cycle, so only a relatively small amount is discharged during the flushing process.

Some growers have had excellent success with automatic flush valves, particularly in large greenhouse facilities with long irrigation runs.

Their experience suggests the benefits can outweigh the additional water use, provided the irrigation schedule is adjusted appropriately.

Another common design question involves irrigation tubing layouts.

Rather than running a single line that dead-ends at the far side of the bench, I generally prefer creating a closed-loop system.

With a closed loop, I also like installing:

• A flush valve at the end of the loop.
• A pressure gauge near the end of the bench.

The closed loop helps equalize pressure throughout the irrigation circuit, while the pressure gauge provides immediate confirmation that the emitters are operating within their intended pressure range.

Flush valves also make routine maintenance much easier.

Tubing size is another factor that's frequently misunderstood.

Different tubing sizes support very different flow capacities.

For example, one tubing size may only be suitable for relatively low flow rates, while a slightly larger tubing diameter can nearly double the amount of water it can deliver.

Simply referring to tubing as "half-inch" or "three-quarter-inch" isn't enough because actual inside diameters and hydraulic capacities vary between products and manufacturers.

Choosing the proper tubing size depends entirely on the required flow rate for that irrigation zone.

If the tubing is undersized, pressure losses increase and uniform irrigation becomes much more difficult to achieve.

The ideal tubing size should always be selected based on hydraulic calculations rather than convention.

When all of these design decisions come together—proper pump sizing, correct tubing diameter, balanced flow rates, pressure monitoring, closed-loop layouts, filtration, and routine maintenance—you end up with an irrigation system that delivers uniform water and nutrient distribution across every plant.

Ultimately, that's the foundation of successful fertigation.

Before implementing advanced irrigation strategies or crop steering techniques, the hydraulic system itself has to be working correctly.

Uniform irrigation always comes first.