Interview Questions for Swimming Pool Automation Systems

Pool automation systems range from simple timers controlling basic functions to sophisticated, integrated systems managing multiple aspects of pool maintenance. Think of them as the ‘brains’ of your pool, taking care of things automatically.

• Basic Timer Systems: These are the most affordable, using simple timers to schedule pump operation. Imagine a basic kitchen timer controlling your pool pump’s on/off cycle. They lack sophisticated features.
• Advanced Programmable Logic Controllers (PLCs): These are the workhorses of sophisticated pool automation. PLCs offer precise control over multiple components, including pumps, filters, heaters, lights, and even chemical dispensing. They are programmable, allowing customization to suit specific pool needs and preferences. This is like having a sophisticated computer managing your pool’s entire operation.
• Cloud-Based Systems: These integrate with the internet, providing remote access and control through smartphones or computers. This is the ultimate in convenience, allowing you to monitor and adjust your pool settings from anywhere in the world. It’s like having your pool in the palm of your hand.
• Integrated Systems: These combine several components, such as pumps, cleaners, and water features, into a single, centrally controlled system. They offer greater efficiency and streamlined operation. These systems represent a holistic approach to pool management.

I have extensive experience programming PLCs for pool automation, primarily using Siemens TIA Portal and Allen-Bradley RSLogix 5000 software. My expertise extends to designing and implementing control logic for various pool components, including pumps, heaters, chemical feeders, and cleaning systems.

For example, I once developed a PLC program that optimized the filtration cycle based on real-time water temperature and clarity sensors. The system adjusted the pump speed and filter backwash schedule dynamically, reducing energy consumption and maintaining optimal water quality. This involved writing ladder logic to manage sensor inputs, setpoints, and output commands to the pool equipment.

This illustrates how PLC programming allows for complex automation and optimization of pool systems beyond the capabilities of simple timers.

Troubleshooting pool automation systems requires a systematic approach. I typically begin by gathering information – what’s not working, when did it start, any recent changes?

• Check the Obvious: Power supply, circuit breakers, fuses. Many issues are simple power problems.
• Sensor Diagnostics: Test sensors (temperature, water level, flow) for proper operation. A faulty sensor can lead to incorrect control actions.
• PLC Program Review: Inspect the PLC program for logic errors or incorrect settings. Simulation tools can help identify issues without affecting the pool.
• Component Testing: Verify individual components like pumps, valves, and actuators. Is the motor working? Is there a blockage?
• Communication Check: For networked systems, verify communication between components and the central control unit. This often involves checking network cables and settings.

For example, if the pump isn’t starting, I would first check the power supply, then the pump motor itself, and finally the PLC program for any commands that might be preventing it from starting. A systematic process is key to efficient troubleshooting.

Safety is paramount when working with pool automation equipment. Electricity and water are a dangerous combination.

• Lockout/Tagout Procedures: Always follow proper lockout/tagout procedures before working on any electrical components. This prevents accidental energization.
• Grounding and Bonding: Ensure all equipment is properly grounded and bonded to prevent electrical shocks.
• Personal Protective Equipment (PPE): Wear appropriate PPE, including safety glasses, rubber gloves, and non-conductive footwear.
• Water Safety: Never work near the pool while the equipment is energized or water is circulating. Be aware of slippery surfaces around the pool.
• Chemical Handling: When working with chemical dispensing systems, follow all safety instructions provided by the chemical manufacturer.

Ignoring safety procedures can lead to serious injury or death. Safety should be the top priority in all aspects of pool automation work.

I’ve worked with a variety of pool pumps, including single-speed, variable-speed, and two-speed models. The automation of these pumps varies depending on their type and the control system in use.

• Single-Speed Pumps: These are typically controlled by simple on/off timers or basic PLC programs. The automation is straightforward, simply switching the pump on and off at scheduled intervals.
• Variable-Speed Pumps: These offer more sophisticated control, allowing for adjustment of pump speed based on various factors (water temperature, clarity, etc.). PLCs with analog input/output modules are needed for precise speed control. This leads to energy savings and better water circulation.
• Two-Speed Pumps: These offer a compromise between single-speed and variable-speed, providing two distinct speeds. Automation involves switching between these speeds based on pre-programmed schedules or sensor input.

For example, a variable-speed pump might be automated to run at a lower speed overnight for gentle circulation and a higher speed during the day for filtration. This would be controlled via a PLC program reading a clock signal and adjusting the pump speed accordingly.

Maintenance and servicing of pool automation systems are crucial to ensure efficient and safe operation. A regular maintenance schedule is essential.

• Regular Inspections: Visually inspect all components for signs of wear, corrosion, or damage. Check for leaks or loose connections.
• Sensor Calibration: Calibrate sensors periodically to ensure accurate readings. Incorrect sensor data can lead to problems.
• Software Updates: Update the PLC program and control software as needed to address bugs or add features. Manufacturers frequently release updates.
• Cleaning: Keep the equipment clean and free of debris. This is especially important for pumps and filters.
• Backwashing/Cleaning Filters: Regularly backwash or clean the pool filter according to the manufacturer’s instructions.

Preventative maintenance significantly reduces the risk of failures and extends the lifespan of the equipment. Think of it like regular servicing for your car; it’s essential for long-term performance.

Cloud-based pool automation systems offer several advantages over traditional systems.

• Remote Access and Control: Manage your pool from anywhere with an internet connection, using a smartphone, tablet, or computer. This is particularly useful for vacation homes or pools that are difficult to access.
• Data Monitoring and Analysis: Gather real-time data on various pool parameters (temperature, pH, water level) and historical trends. This helps identify potential issues before they become major problems.
• Automated Alerts and Notifications: Receive alerts for critical events, such as low water levels, equipment failures, or chemical imbalances. This ensures timely intervention and prevents costly damage.
• Enhanced Security: Cloud platforms often have enhanced security measures to protect against unauthorized access.
• Easy Integration: Many cloud-based systems offer seamless integration with other smart home devices and services.

Cloud-based systems provide a level of convenience, control, and insight that is unmatched by traditional systems. Imagine getting an alert on your phone if a pump fails while you’re away, allowing you to take action remotely.

Integrating different pool automation components requires a systematic approach. It’s like building with LEGOs – each piece needs to connect correctly to the whole system. My experience covers a wide range of components, including pumps, filters, chlorinators, heaters, lighting, and robotic cleaners. I’ve worked with both wired and wireless systems, from simple setups to complex, multi-zone installations.

For example, I recently integrated a new variable-speed pump with an existing automated control system. This involved understanding the communication protocols (e.g., BACnet, Modbus) of both the pump and the controller to ensure seamless operation and data exchange. I also had to configure the control system to adjust the pump speed based on real-time sensor data, like water temperature and flow rate. This resulted in significant energy savings and optimized filtration. Another project involved integrating a smart phone app for remote control of the entire system, requiring meticulous configuration and testing to ensure system stability and security.

• Understanding the communication protocols (e.g., BACnet, Modbus, TCP/IP)
• Careful wiring and connection of components
• Configuration of the central control system
• Testing and troubleshooting to ensure proper operation

Diagnosing faults in pool automation systems is a methodical process. Think of it as detective work. I start by gathering information: checking error logs, visually inspecting components, and testing sensors. I use multimeters to check voltage and current, and specialized tools for testing communication signals.

For instance, if the pump isn’t turning on, I’d first check the power supply and fuses. If the power is good, I’d then check the control signals going to the pump using a multimeter. If the signals are absent or incorrect, I’d trace the problem back to the control system, possibly checking for software glitches or faulty wiring. I utilize troubleshooting flowcharts and diagnostic software provided by the manufacturers to isolate and resolve the issue efficiently. Remote access to the system via software allows for faster diagnosis and sometimes remote repair.

My approach involves a combination of:

• Visual inspection of components
• Testing with multimeters and specialized tools
• Reviewing error logs and diagnostic reports
• Following systematic troubleshooting procedures
• Utilizing manufacturer-provided diagnostic software

I’m proficient in various software and tools used for programming pool automation systems. This ranges from simple programming interfaces for smaller systems to complex SCADA (Supervisory Control and Data Acquisition) software for larger, more integrated ones.

I’ve worked with software from major manufacturers such as Pentair, Hayward, and Jandy. This includes their dedicated programming software for configuring controllers, setting schedules, and monitoring system performance. I’m also familiar with industry-standard programming languages like Ladder Logic (used in PLCs). For more advanced systems, I’ve used SCADA software packages that provide a centralized view of the entire automation system allowing for comprehensive monitoring, control, and data logging. I’m also adept at using diagnostic tools and network analyzers to troubleshoot communication issues and optimize system performance.

• Manufacturer-specific programming software (Pentair, Hayward, Jandy)
• SCADA software for large-scale systems
• Ladder Logic programming for PLCs
• Network analyzers and diagnostic tools

Sensors are the eyes and ears of a pool automation system. They provide critical data, enabling the system to make intelligent decisions. My experience includes working with a wide variety of sensors:

• Water level sensors: These sensors monitor water levels to prevent overflows or dry runs. I’ve used both float switches and ultrasonic sensors, each with its own advantages and disadvantages.
• Temperature sensors: Essential for controlling heaters and monitoring water temperature for optimal swimming conditions. These can be resistance temperature detectors (RTDs) or thermistors.
• Flow sensors: Monitor water flow through the filter to ensure proper filtration and identify potential blockages. These often use mechanical or ultrasonic technologies.
• pH and ORP sensors: Measure water chemistry to ensure proper sanitation and prevent corrosion. These are crucial for automated chemical control systems.
• Turbidity sensors: Measure water clarity and trigger cleaning cycles when necessary.

Understanding the limitations and calibration requirements of each sensor type is crucial for accurate system operation. For example, biofouling can impact the accuracy of pH and ORP sensors, requiring regular cleaning or replacement.

Emergency situations require a swift and decisive response. My experience includes handling various failures, from pump malfunctions to power outages. My priority is always safety.

If a critical system component fails (e.g., the pump stops during a high-temperature situation), I’ll immediately assess the situation, taking safety precautions like turning off power to affected components if necessary. Then I initiate backup procedures (if available). If backup is not in place, I begin troubleshooting immediately, prioritizing restoring essential functions and minimizing further damage or safety risks. For example, if a power outage occurs, a battery backup system should kick in to maintain essential functions. If not, manual intervention may be required and safety is paramount.

Thorough documentation and preventative maintenance are crucial in minimizing emergencies and enabling quick recovery.

• Immediate safety assessment
• Initiation of backup procedures
• Rapid troubleshooting and repair
• Clear communication with stakeholders

Energy efficiency is a major concern in pool automation. My experience involves implementing various strategies to reduce energy consumption.

This includes using variable-speed pumps, which adjust their flow rate based on demand, resulting in significant energy savings compared to traditional single-speed pumps. I also optimize filtration cycles based on water usage and sensor data. Smart scheduling, where the pool systems run only when needed, also saves energy. Properly sizing pumps and filters based on pool characteristics is crucial to prevent over-operation and associated energy waste. Additionally, I integrate energy-monitoring tools to track energy use and identify areas for improvement. For instance, implementing a system that reduces the heater operation during peak energy demand periods.

• Variable-speed pumps
• Optimized filtration cycles
• Smart scheduling
• Proper equipment sizing
• Energy monitoring and analysis

Remote monitoring and control offer significant advantages in pool automation, providing convenience and efficient troubleshooting. I have extensive experience in setting up and managing remote access systems. This often involves utilizing cloud-based platforms and secure communication protocols.

For example, I’ve configured systems that allow clients to control pool features (e.g., pumps, lights, heaters) through smartphone apps. These apps also provide real-time data on water temperature, pH levels, and other parameters. Additionally, remote diagnostics capabilities enable quick identification and resolution of potential problems before they escalate. Security is paramount, so I always use robust security protocols and encryption to protect the system from unauthorized access. It’s like having a remote control for your entire pool system, allowing for proactive management and efficient energy use, plus the ability to identify problems before they become major issues.

• Cloud-based platforms and mobile apps
• Secure communication protocols (e.g., HTTPS, VPN)
• Real-time data monitoring
• Remote diagnostics and troubleshooting
• Robust security measures

Pool automation systems rely on various communication protocols to exchange data between different components. Think of these protocols as the ‘languages’ devices use to talk to each other. The most common ones include:

• Wi-Fi: A ubiquitous standard, offering ease of setup and wide compatibility. Many controllers and sensors use Wi-Fi to communicate with the central hub and potentially with cloud services for remote monitoring and control.
• Zigbee: A low-power, mesh networking protocol ideal for sensors and actuators spread throughout a pool area. It’s excellent for battery-powered devices because it’s energy-efficient. Zigbee allows for robust communication even in areas with obstacles.
• Z-Wave: Similar to Zigbee in its low-power nature, Z-Wave is another mesh networking protocol. Its strong security features make it popular for high-security applications. It’s commonly used in smart home ecosystems and can be integrated with other smart home devices seamlessly.
• Bluetooth: Useful for short-range communication, Bluetooth finds applications in configuring and interacting with individual components directly from a smartphone or tablet. It’s less suitable for extensive network communication.
• Ethernet (wired): Offers a highly reliable and faster connection, though it involves cabling. This is often used for connecting controllers to a central network management system or for integrating with wired smart home systems. It’s less flexible than wireless protocols.

The choice of protocol depends on factors like range, power consumption, security needs, and the overall architecture of the pool automation system. For example, a large commercial pool might leverage a combination of Ethernet and Wi-Fi for robust and expansive communication, while a smaller residential pool might primarily use Wi-Fi or Zigbee.

Cybersecurity is paramount in pool automation. A compromised system could lead to equipment damage, water waste, or even safety hazards. Here’s how we ensure robust cybersecurity:

• Strong Passwords and Authentication: Enforcing strong, unique passwords for all system components and using multi-factor authentication wherever possible.
• Regular Software Updates: Keeping all firmware and software up-to-date patches vulnerabilities exploited by hackers.
• Network Segmentation: Isolating the pool automation network from other home networks limits the impact of a breach. This is similar to having a separate ‘guest’ Wi-Fi network, but for your pool’s devices.
• Firewall Protection: Implementing a firewall to control network traffic, preventing unauthorized access to the system.
• Intrusion Detection Systems: Monitoring network traffic for suspicious activity and alerting administrators to potential threats.
• Data Encryption: Encrypting data both in transit and at rest to protect sensitive information.

We also advise clients on best practices, such as avoiding default passwords and changing them immediately upon installation. Furthermore, choosing reputable vendors with a demonstrated commitment to security is crucial. Think of it like using strong locks and a secure alarm system for your home—multiple layers of protection are essential.

Integrating pool automation with other smart home systems can present challenges, primarily due to differences in protocols and standards. Imagine trying to connect two devices that speak completely different languages!

• Protocol Incompatibility: Different systems may use different communication protocols (e.g., Zigbee vs. Z-Wave), making direct integration difficult. This often necessitates using a central hub or gateway that acts as a translator.
• Data Format Differences: Even when protocols are compatible, data formats can vary, requiring custom integrations or middleware to ensure seamless data exchange.
• Security Concerns: Ensuring the security of the integrated system is vital. A vulnerability in one system could potentially compromise the entire network.
• Vendor Lock-in: Some systems might be proprietary and don’t easily integrate with others, limiting flexibility and future upgrades.

To overcome these, we use home automation platforms like Home Assistant or smart home hubs that support multiple protocols. This allows us to act as a bridge between different systems, translating data and commands to create a unified, controlled environment. Careful planning during the initial design phase is key to minimizing integration headaches.

I’ve worked extensively with various pool heater types and their automation. The automation aspect usually involves controlling the heater’s on/off cycles and potentially its temperature based on factors like time of day, ambient temperature, and water temperature.

• Gas Heaters: These are typically controlled by a thermostat, either directly wired to the heater or via a relay controlled by the automation system. Automation allows for scheduling, ensuring the pool is heated only when needed, saving energy and costs.
• Heat Pumps: Heat pumps offer efficient heating. Their automation is often more sophisticated, involving control over the compressor and fan speed to adjust the heating capacity based on the desired water temperature and ambient conditions. The automation system can monitor both water and ambient temperatures, adjusting the heat pump accordingly.
• Electric Heaters: These are simpler to automate, generally using a relay to switch the heater on and off based on programmed schedules or sensor readings. However, due to their high energy consumption, smart automation is even more critical to control costs.

In all cases, robust safety features are crucial. The automation system needs to incorporate safeguards to prevent overheating, over-pressure, and other potential hazards. Real-time monitoring of heater operation is essential, allowing for immediate alerts in case of malfunctions. I’ve developed custom algorithms to optimize energy use by leveraging weather forecasts and predicted pool usage.

Pool lighting automation offers both convenience and aesthetic appeal. We typically use programmable controllers and dimmers to control the intensity and color of pool lights. This allows for:

• Scheduled Lighting: Setting the lights to turn on and off at specific times, creating a consistent ambiance. This could be linked to sunrise/sunset times or customized schedules based on pool usage.
• Remote Control: Adjusting lighting settings remotely via a smartphone app or other control interface. This is great for convenience and even enhances security by making the pool appear occupied when away from home.
• Dynamic Lighting Effects: Creating captivating lighting displays with color-changing LED lights, which can be programmed for different occasions or moods.
• Integration with other systems: Pool lighting can be integrated with other smart home elements, such as music systems, for a fully synchronized, immersive experience.

I’ve worked with a variety of lighting systems, from simple on/off controls to sophisticated RGBW LED systems that can create an extensive range of colors and dynamic lighting scenes. The key is to ensure smooth integration with the overall automation system and to prioritize energy-efficient solutions. I also emphasize safety protocols, ensuring low voltage systems or properly grounded higher voltage systems, especially in underwater lighting scenarios.

Data from pool automation systems provides invaluable insights into pool operation and maintenance. This data includes water temperature, chemical levels, pump runtimes, energy consumption, and more.

We use dedicated software platforms and dashboards to visualize and interpret this data. This allows us to identify trends, detect potential problems early on, and optimize pool operations. For example:

• Predictive Maintenance: Analyzing pump runtimes and energy consumption can help predict when maintenance is needed, preventing costly breakdowns. Think of it like a car’s maintenance light – but for your pool equipment.
• Chemical Level Monitoring: Continuous monitoring of chemical levels allows for proactive adjustments, ensuring the pool water stays balanced and safe. This can prevent costly chemical imbalances and health concerns.
• Energy Optimization: Analyzing energy consumption patterns helps identify areas where efficiency can be improved, reducing operating costs. This often involves smart scheduling of equipment, such as pumps and heaters.

We provide clients with clear, easy-to-understand reports and visualizations, empowering them to actively manage their pool’s health and minimize operational costs. The data-driven insights we provide go beyond simple monitoring, aiding in preventative maintenance and overall efficiency optimization.

Robotic pool cleaners are increasingly integrated into automation systems, significantly enhancing efficiency and convenience. Integration typically involves scheduling cleaning cycles, monitoring cleaner status, and potentially receiving alerts if problems arise.

• Scheduling: Automation allows you to schedule cleaning cycles based on your preferences, ensuring the pool is consistently clean without manual intervention. This could be a daily, weekly, or even custom schedule.
• Status Monitoring: The automation system can track the cleaner’s operational status, including battery level, cleaning time, and any errors encountered. This proactive monitoring prevents unexpected downtime.
• Integration with other systems: The cleaner’s operation can be linked to other aspects of the pool automation, such as adjusting the pool pump’s operation during the cleaning cycle for optimal performance.

Different robotic cleaners use various communication protocols, so the automation system needs to be compatible. I have experience integrating various models using Wi-Fi, Bluetooth, and even dedicated communication protocols specific to certain cleaner brands. Proper integration ensures optimal cleaning performance and seamless operation within the overall pool automation ecosystem.

Pool water chemistry control systems automate the crucial task of maintaining ideal water balance. They integrate with automation systems to ensure consistent water quality, reducing manual intervention and the risk of imbalances. There are several types:

• Basic Controllers: These use sensors to measure pH and chlorine levels, activating pumps and dispensing chemicals as needed. Think of them as a simple thermostat for your pool’s chemistry.
• Advanced Controllers: These offer more sophisticated features like dissolved oxygen monitoring, temperature control, and integration with other pool equipment, such as automatic cleaners. They’re like a smart thermostat, learning patterns and optimizing performance.
• Automated Dispensing Systems: These systems precisely dispense chemicals based on real-time water analysis, offering extremely precise control and reducing chemical waste. These are analogous to a high-precision dispensing robot in a pharmaceutical lab.

Integration with automation typically involves connecting these systems to a central control panel or software platform. This allows for remote monitoring, scheduling of tasks (e.g., chemical additions), and automated alerts if parameters fall outside the desired range. For example, an advanced controller might automatically send a notification to your phone if the pH level drops too low.

I’m familiar with a wide range of manufacturers, including Pentair, Hayward, Jandy, and Zodiac. Each offers unique features and strengths. For instance:

• Pentair IntelliChlor: Known for its salt chlorine generation system and robust automation capabilities, offering excellent control and energy efficiency.
• Hayward OmniLogic: Offers a user-friendly interface and extensive system integration, allowing control of multiple pool components from a single platform.
• Jandy Aqualink RS: A reliable and versatile system suitable for a variety of pool sizes and features, known for its compatibility with third-party devices.
• Zodiac iAquaLink: Provides remote access and control through a mobile app, enhancing convenience and user experience.

My experience extends to both residential and commercial systems, enabling me to understand the specific needs and considerations for each application. I can effectively troubleshoot and configure systems from various manufacturers, adapting my approach based on the specific technology and features involved.

I once encountered a complex problem with a Pentair IntelliChlor system where the salt cell wasn’t generating chlorine despite showing no errors. My approach was systematic:

1. Gather Information: I started by reviewing the system logs, checking water parameters (salt level, pH, etc.), and visually inspecting all connections and components.
2. Isolate the Problem: The logs indicated normal power to the cell, but the chlorine generation remained low. I then tested the flow rate through the cell, discovering it was significantly reduced due to a partially clogged filter.
3. Implement Solution: Cleaning the filter restored the flow, and the salt cell began functioning correctly.
4. Preventative Measures: To prevent future issues, I recommended a more frequent filter cleaning schedule and provided training to the pool owner on maintaining proper water flow.

This highlights the importance of a systematic approach, combining technical knowledge with careful observation and analysis. Often, the solution isn’t immediately obvious, and a methodical investigation is key.

Prioritization of tasks depends on several factors: system criticality, urgency, and potential impact. I use a combination of methods:

• Urgency/Impact Matrix: I assess each system’s current status and potential consequences of a malfunction. Systems impacting safety or causing significant water quality degradation are prioritized higher.
• Scheduling and Time Management: I create a schedule based on the urgency matrix, allocating time slots for each task while considering travel time and potential complications.
• Remote Monitoring: I leverage remote monitoring capabilities to track system performance and identify potential issues proactively, allowing for preemptive maintenance.

For example, a malfunctioning pump impacting water circulation is a higher priority than a minor adjustment needed for the lighting system. This approach ensures efficiency and prevents minor issues from escalating into major problems.

Key Performance Indicators (KPIs) for evaluating pool automation systems include:

• Water Quality Consistency: Measured by the stability of pH, chlorine levels, and other relevant parameters.
• Energy Efficiency: Monitoring energy consumption of pumps, heaters, and other components.
• System Uptime: Tracking the percentage of time the system is operational without faults.
• Chemical Usage: Tracking chemical consumption to identify potential inefficiencies or leaks.
• Maintenance Frequency: Measuring the frequency of maintenance tasks, aiming for minimization.
• User Satisfaction: Assessing the user experience through feedback and usability surveys.

These KPIs provide quantifiable data to measure the effectiveness of the automation system and identify areas for improvement.

Staying current in this rapidly evolving field requires a multi-pronged approach:

• Industry Publications and Websites: I regularly read publications like Pool & Spa News and relevant trade websites to stay informed about the latest advancements.
• Trade Shows and Conferences: Attending industry events provides valuable insights into new technologies and networking opportunities.
• Manufacturer Training: Participating in manufacturer training programs ensures familiarity with the latest features and troubleshooting techniques.
• Online Courses and Webinars: Utilizing online learning platforms to enhance technical skills and knowledge.

Continuous learning is essential to maintain a high level of expertise in this dynamic industry.

Thorough documentation is crucial for efficient maintenance and troubleshooting. My documentation process includes:

• System Diagrams: Detailed diagrams illustrating the system’s components, wiring, and connections.
• Configuration Settings: Records of all system settings, including chemical dispensing schedules and sensor calibration data.
• Maintenance Logs: Detailed records of all maintenance activities, including dates, performed tasks, and any issues encountered.
• Troubleshooting Guides: Step-by-step procedures for resolving common problems.
• Parts Lists: Lists of all system components, including part numbers and suppliers.

I use a combination of digital and physical documentation methods to ensure accessibility and prevent data loss. This systematic approach minimizes downtime and streamlines the maintenance process, ensuring the long-term performance and reliability of the automated pool system.