Troubleshooting Low Pressure in One Sprinkler Zone: 10 Likely Culprits

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  • Post last modified:June 6, 2023
  • Reading time:16 mins read
One possible cause of low pressure in one zone of a sprinkler system is a faulty backflow preventer valve that is not fully open. Another possible cause is a leak or break in the water line. Additionally, if the pressure is low at only one or two sprinkler heads, they may simply be dirty or clogged.

Having low pressure in one zone of your sprinkler system can be frustrating and time consuming to troubleshoot. However, with a little knowledge and guidance, you can quickly identify the cause of the problem and repair it. In this article, we’ll discuss some of the possible causes behind low pressure in a sprinkler system. We’ll look at issues like clogged filters, worn components, improper sizing of pipes, leaks in the system and more. Understanding these potential causes will help you diagnose and resolve any issues quickly so that you can get back to enjoying your beautiful lawn!

Key Takeaways

  • Low pressure in one zone of a sprinkler system can be caused by a variety of factors, including clogged filters, worn components, partially open/closed isolation valves, inadequate pressure from the main source, improperly sized pipes, and leaking pipes.
  • To resolve low pressure issues, it is important to check for visible signs of damage or wear on the regulator, inspect all pipes and connections, consult with an expert before proceeding with repairs or replacements, ensure all elements of the system are in balance, and check for obstructions in spray heads or zone valves.
  • Regular inspection of sprinkler heads is important to ensure they are not defective, stuck, clogged, or incorrectly adjusted, as even one malfunctioning head can affect the performance of the entire zone.
  • The use of a pressure vacuum breaker (PVB) is required by most local codes to protect against water contamination caused by backflow, and routine inspection is important to check for damage or deterioration. Other factors contributing to low pressure include rusting, leaking, or cracking PVBs, leaks or breaks in water lines leading to one zone, organic matter accumulation inside sprinkler heads, and broken nozzles caused by lawn mowers or weeds.

Clogged Filter

If the pressure is low at just a few sprinkler heads, it could be because they’re clogged or dirty – so check your filter! A clogged filter can impede water flow and reduce water pressure in an individual zone. It’s important to inspect the filter regularly to make sure it isn’t blocked by debris, dirt, and other substances. If you see any blockage in the filter, clean it out immediately. Additionally, you should also check for any blockages in the spray head or zone valve that could impact water pressure.

If these components are not free of obstructions, then the water won’t be able to travel freely through them which will result in low water pressure throughout the zone. To restore normal water pressure levels, take apart these components and remove all obstructions from inside them. You may need to use a specialized tool such as a brush or forceps to clear stubborn build-ups of dirt and debris from within them.

Once all obstructions have been cleared away, put everything back together again and turn on the main valve for that zone. You should find that your system has returned back to its correct operating level with sufficient water pressure running through it once more.

Worn Components

Check your sprinkler system for worn components, as these can be the culprit behind poor irrigation. Old valves, such as backflow preventers and zone valves, may be leaking or not opening fully due to age or rusting. Similarly, old sprinkler heads may be weak and unable to handle water pressure properly, resulting in diminished spray coverage and low pressure. If you have a valve box with an isolation valve that is partially open or closed shut, this could also affect the pressure of just one zone of your irrigation system.

Examine all the components of your sprinkler system for any signs of wear and tear. Look for corrosion on metal parts; check rubber seals to see if they are still soft and flexible; inspect plastic parts for cracks or breaks. Finally, make sure there are no obstructions in the pipes leading to each sprinkler head – clogs can cause backpressure which reduces flow rate throughout all zones.

If you suspect that one of your components is worn out, replace it immediately with a new part from a reputable supplier in order to ensure optimal performance across all zones in your sprinkler system.

Low Water Pressure from Main Source

You might notice weak water flow in certain parts of your yard, which could be the result of inadequate pressure from the main source. To understand what is happening, you need to check the entire system from start to finish. This includes:

  1. Checking the garden hose for any kinks or blockages that will restrict flow;
  2. Ensuring that there is a water pressure regulator installed and set correctly;
  3. Verifying whether the main water valve supplying your sprinkler system is functioning properly.

If all these components are working as designed, then you may need to consider replacing parts of the system that have worn out or become clogged over time. In this case, it may be necessary to replace valves or pipes within the sprinkler system itself in order to restore adequate pressure throughout the zone.

Improperly Sized Pipes

You’ll want to make sure your pipes are the right size for your sprinkler system, as otherwise you may not get the water pressure you need throughout the entire yard. The main water supply coming from the street needs to be regulated and equalized with the pipe work leading into your yard. This is done by using pressure regulators on each end of piping that connects to both sources.

Main Water SupplyPressure RegulatorsWater Pipe Work

In order for your sprinkler system to function effectively, it is important that all elements are in balance, including the sizes of pipes used. If any part of the piping leading to or inside your yard is too small, it could cause a noticeable decrease in water pressure at one zone of your sprinkler system. It’s also important that any valves controlling flow between zones are working properly and not restricting the flow of water unnecessarily. Not only will this affect water pressure, but also leave certain areas dry when other areas become oversaturated with water.

Leaks in System

Leaking pipes can wreak havoc on a sprinkler system, resulting in uneven water distribution and decreased performance. Low pressure in one zone of the sprinkler system can be caused by a number of factors, including leaks or broken lines in the system. Here are 4 common signs that indicate you may have leaks:

  1. Unusually wet areas around the sprinklers, even when they’re not running
  2. Uneven distribution of water
  3. Discoloration to the soil around certain sprinklers
  4. A decrease in pressure at one or more valves

When any of these signs appear, it’s important to act quickly to prevent further damage and costly repairs down the line. Check for visible broken lines or leaking joints and repair them immediately with new parts or fittings if necessary. Additionally, inspect all pipes and connections for wear-and-tear that could cause future issues like corrosion or weakened seals over time. Taking these proactive steps will help ensure your sprinkler system performs as expected for years to come!

Defective Pressure Regulator

A defective pressure regulator can wreak havoc on your sprinkler system, leaving you feeling frustrated and helpless. A pressure regulator is a type of valve that reduces the water pressure in the system, allowing for consistent performance in multiple zones. If the pressure regulator is not functioning correctly, it can cause low water pressure in one zone of the sprinkler system. This can be caused by a variety of factors, such as a broken spring or diaphragm within the regulator, an incorrect setting on the valve or a buildup of debris that prevents proper flow.

In order to diagnose if you have a defective pressure regulator causing low water pressure in one zone, you should check several components. First, inspect all pipe fittings and connections to ensure they are tight and free from leaks. Next, check for visible signs of damage or wear on the regulator itself such as cracks or corrosion. Finally, measure the incoming water pressure at both ends of the valve using a gauge and compare them to see if there is any difference between them.

If these tests indicate that your problem may be due to a faulty pressure regulator then it will need to be replaced with one that meets local codes and has been properly sized for your system’s requirements. It’s important to remember that any change made to your sprinkler system could have drastic impacts so it’s best practice to consult with an expert before proceeding with repairs or replacements.

Poorly Positioned Valves

If you’re experiencing problems with your sprinkler system, poorly positioned valves could be to blame. Valves control the flow of water in a sprinkler zone, so if they are not properly adjusted, it can cause an unequal distribution of pressure throughout the system. If one zone has significantly lower pressure than others, it’s likely due to a faulty valve. This could include a loose solenoid or other components that are no longer working correctly.

To diagnose this problem, first check for any visible signs that the valves are misaligned. Then look for any loose connections that may have come undone over time. If these issues are present and you’re still seeing lower pressure in one zone than in others, then it could mean there’s something wrong with the internal parts of the valve itself.

In order to solve this issue, you’ll need to replace or repair the faulty valve component by either calling an expert or attempting to do it yourself depending on your level of expertise and comfort with plumbing repairs. It may also be necessary to adjust other valves within the same zone as part of troubleshooting process so that all areas receive equal pressure throughout the sprinkler system.

Defective Sprinkler Heads

Now that we have discussed the possible cause of low pressure in one zone of a sprinkler system due to poorly positioned valves, let’s shift our focus to defective sprinkler heads. If the problem zone does not have any faulty backflow preventer valves or damaged lines, then it is likely that there is an issue with one or more of the sprinkler heads in this area. A stuck solenoid, for example, could be preventing water from flowing out of some heads. This may lead to uneven water distribution and low pressure throughout the entire zone.

In addition to solenoid issues, other problems can arise with sprinkler heads such as clogs, broken nozzles, and incorrect adjustments. Clogs may occur if organic matter accumulates inside a head and blocks the flow of water through it. Broken nozzles can happen if they are hit by a lawn mower or get tangled in weeds which cause them to crack or break off completely. Finally, incorrect adjustments mainly affect rotary spray heads; if they are set too close together then they end up competing for water leading to lower pressure than necessary.

It is important to check all sprinkler heads in an affected area because even one malfunctioning head can cause problems for an entire zone’s performance – resulting in low pressure and poor coverage overall. This is why inspecting these components regularly will help keep your system running efficiently and ensure that each area receives adequate irrigation regardless of how many sprinklers are installed there.

Pressure Vacuum Breaker

You may need to ensure that the pressure vacuum breaker in your sprinkler setup is functioning properly, as it can have a significant impact on the effectiveness of the irrigation. A pressure vacuum breaker (PVB) is a backflow preventer device that helps protect against water contamination caused by backflow from an irrigation system. This device prevents potentially hazardous water from entering into the public water supply and is required by most local codes when installing a sprinkler system.

It is important to routinely inspect the PVB for any signs of damage or deterioration, such as rusting, leaking, or cracking. If left unchecked, these issues can lead to decreased water pressure in one zone of your sprinkler system which can cause problems with your irrigation coverage. Additionally, if you suspect there may be a leak or break in the water line leading to one zone of your sprinkler system, this can also contribute to decreased water pressure as well.

Frequently Asked Questions

How do I know if my backflow preventer valve is faulty?

To check if your backflow preventer valve is faulty, look for signs of leakage or corrosion on the valve stem. If this is present, you may need to replace it. Additionally, try opening and closing the valve to see if it functions properly.

What is the best way to identify a leak or break in a water line?

To identify a leak or break in a water line, check for visible cracks or holes. Then, look for signs of water leaking out or pooling around the area. Finally, use an acoustic leak detector to pinpoint the exact location of the break.

Are there any other causes of low pressure in my sprinkler system besides the ones listed?

Yes, other causes of low pressure in your sprinkler system can include a blocked or damaged spray nozzle, an incorrectly adjusted pressure regulator, or a pump that is malfunctioning.

How often should I clean or replace my sprinkler heads?

You should clean your sprinkler heads every 1-2 months or replace them every 3-5 years depending on their condition. Regular maintenance will ensure optimal performance and pressure in your system.

Can I adjust the pressure regulator on my own or do I need to call a professional?

You can adjust the pressure regulator on your own, but be aware that it requires careful attention and knowledge. It’s best to contact a professional if you’re unsure about the process.


It’s important to understand the various causes of low pressure in one zone of a sprinkler system so you can diagnose and fix the issue quickly. Clogged filters and worn components can reduce water flow, while a low water pressure from the main source or improperly sized pipes can also cause issues. Leaks, defective pressure regulators, poorly positioned valves, and defective sprinkler heads are all factors that need to be considered when diagnosing low pressure in one zone. With some investigation and troubleshooting, you should be able to identify and fix the issue quickly so your sprinkler system runs like new again.