Opening your swimming pool for the season is a critical task that sets the stage for clean, safe, and enjoyable water throughout the summer months. One of the first decisions pool owners must make after uncovering the pool is whether to start the pump on the filter setting or the recirculate setting. This seemingly small choice can have a significant impact on the effectiveness of your startup process, water clarity, chemical distribution, and overall pool maintenance.
In this detailed article, we will explore the key differences between pool filter and recirculate settings, explain when and why you should choose one over the other, and walk you through the best practices for opening your pool. Whether you’re a seasoned pool owner or a first-time user, understanding these fundamentals will make your pool startup smoother and more effective.
Understanding Pool Filter and Recirculate Settings
Before diving into the best setting for opening your pool, it’s important to understand what these two modes do and how they affect water circulation and filtration.
What Is the Filter Setting?
The filter setting is the standard and most commonly used position for your pool’s multiport valve. In this mode:
- Water is drawn from the pool and passed through the filter system (sand, DE, or cartridge).
- The filter traps dirt, debris, and contaminants, returning clean water to the pool.
- This is the preferred setting for normal pool operation after startup.
The filter setting is ideal for keeping the pool clean once it’s balanced, but it may not always be the best choice at the very beginning of the opening process if the water is heavily contaminated.
What Is the Recirculate Setting?
The recirculate setting is a bypass mode that:
- Prevents water from going through the filter.
- Re-circulates water directly back into the pool after passing through the pump and heater (if applicable).
- Helps mix and distribute chemicals faster without the filter capturing them.
This setting can be useful during the initial stages of pool opening when you’re adding chemicals and don’t want them to be stripped out by the filter before they can take effect.
Why the Opening Process Matters
The way you start your pool at the beginning of the season has a lasting impact on its performance throughout the year. A proper startup ensures that:
- Water is balanced chemically (pH, alkalinity, calcium hardness).
- Algae and bacteria are prevented or eliminated early.
- The filter system is not overwhelmed by debris or contaminants.
- Equipment operates efficiently and lasts longer.
One of the most common mistakes during startup is running the system on the filter mode immediately after adding clarifiers or algaecides, which can reduce their effectiveness. This is where the recirculate setting becomes valuable.
When to Open the Pool on Recirculate Mode
To understand when to use the recirculate setting, you must first consider the state of your pool water after the winter. Pools that have not been properly winterized or maintained during the off-season may experience:
- Discoloration (green, brown, or cloudy water)
- Algae growth
- Unbalanced chemical levels
If your pool falls into any of these categories, starting on the recirculate setting may be the best approach.
Recirculate Advantages During Pool Opening
There are several reasons why recirculate might be the better starting point when opening your pool:
1. Faster Chemical Mixing:
When you add clarifiers, algaecides, or pH adjusters, the recirculate mode prevents these chemicals from being filtered out before they’re fully dispersed. This ensures a more uniform chemical balance.
2. Preventing Filter Overload:
Pools that have gone unattended for months often have a high level of suspended particles and organic matter. Sending this directly through the filter can clog it prematurely, reducing its efficiency and possibly damaging the system.
3. Avoiding Costly Backwashing:
If you start with the filter setting and the water is very cloudy or full of contaminants, you may need to backwash the filter repeatedly. This wastes water and shortens the life of your filter media.
Best Practices When Using Recirculate for Startup
If you decide to use the recirculate setting, follow these best practices:
- Run for a limited time (up to 6–8 hours): Use recirculate only until chemicals are sufficiently mixed—typically one or two pump cycles.
- Bypass the heater: If you have a pool heater, ensure it is not engaged during recirculate unless specifically designed for it.
- Monitor chemical levels: Test the pool water frequently to ensure it is stabilizing.
- Switch to filter afterward: Once chemicals are evenly distributed, change the valve to the filter setting to start cleaning and clarifying the water.
When to Open the Pool on Filter Mode
On the other hand, in some cases, starting directly on filter mode is appropriate. This is especially true for pools that have been well-maintained over the winter or those with minimal contamination.
Advantages of Starting on Filter Mode
- Promotes circulation and filtration early: If the water is relatively clean, starting on filter helps remove any minor dirt or organic material.
- Maintains water clarity faster: The filter begins removing particles immediately, which can result in clearer water sooner.
- Reduces manual cleaning: Running the filter can naturally pull in surface debris and bottom sediments if the pool is skimmed and vacuumed properly.
Best Practices When Using Filter for Startup
If you choose to start on the filter mode, here are some guidelines to follow:
- Ensure the filter is clean and functional: Before winterizing, service your filter media and check for any damage to valves or tanks.
- Add water-soluble chemicals sparingly: Distribute them evenly and consider reducing the amount to avoid them being stripped out too quickly.
- Keep a close eye on pressure: If the filter pressure rises quickly, it may be a sign of buildup, requiring frequent backwashing.
Comparing Filter and Recirculate Settings: Pros and Cons
To help you better understand the appropriate use of each setting during pool opening, let’s summarize the key pros and cons in a table.
| Setting | Pros | Cons |
|---|---|---|
| Filter |
|
|
| Recirculate |
|
|
How to Determine Which Setting Is Best for Your Pool
Ultimately, the choice between filter and recirculate depends on the condition of your pool water. Here are some questions to ask yourself when opening your pool:
- Is the water clear or cloudy? If cloudy or green, recirculate may be better initially.
- Did you winterize properly? Properly closed pools may start on filter with little initial buildup.
- Did algae or staining occur during the off-season? If yes, starting with recirculate lets you address chemical dosing more effectively.
- Is your filter clean and functional? A well-maintained filter can handle early filtration better.
Step-by-Step Guide to Opening a Pool: Choosing Between Filter and Recirculate
To help you apply this knowledge effectively, here’s a practical, step-by-step opening process that includes setting selection.
Step 1: Remove Winter Cover and Gutter
Start by removing the pool cover, winterizing pillows, and leaf netting. Use a cover pump or submersible pump to eliminate excess water from the cover before removing it. Clean the cover and store it in a dry, shaded place.
Step 2: Skim and Vacuum the Pool
Before starting the pump, skim large debris from the water and vacuum the pool floor to reduce initial contaminants. This also helps reduce strain on the filter system.
Step 3: Refill Water Level if Necessary
During the winter, evaporation or runoff may lower your water level. Refill the pool so the water reaches the middle of the skimmer intake.
Step 4: Reconnect Equipment and Prime the Pump
Reattach the pump basket, inspect and reconnect the return jets, skimmer, and main drain. Prime the pump and ensure a solid water flow to prevent dry operation.
Step 5: Choose Recirculate or Filter Based on Water Quality
At this stage, examine the water. If it appears reasonably clean and balanced, start on filter. If it’s cloudy or green, start on recirculate for a short duration.
Step 6: Add Initial Chemicals
If using recirculate, add algaecide, clarifier, and pH adjusters now. Let the system run for a few hours to ensure good mixing.
Step 7: Switch to Filter and Begin Regular Filtration
After chemicals are distributed, switch the valve to filter. Run the pump for 8–12 hours daily for the first few days and monitor the pressure.
Step 8: Test and Adjust Water Chemistry
After 24–48 hours of filtration, test the water using professional-grade strips or a liquid test kit. Adjust chlorine, pH, total alkalinity, and calcium hardness as needed.
Maintenance After Startup: Which Mode Should You Use?
Once your pool has been opened successfully and the water is clear and chemically balanced, the answer becomes straightforward: always use the filter mode during normal operation.
Leaving the pool on recirculate for extended periods can lead to:
- Reduced water clarity over time
- Algae spore resurgence
- Unstable chemical levels
- Potential water stratification (poor water movement)
Use the recirculate setting only during short, intentional periods during startup or when you’re adding specific chemicals that need even distribution before filtration.
Common Mistakes to Avoid When Opening a Pool
To ensure a successful opening, avoid these common pitfalls:
- Starting the pump without priming: This can damage the impeller or cause air locks.
- Adding too many chemicals too quickly: Overdosing can lead to cloudy water, filter damage, or chemical imbalance.
- Leaving the system on recirculate for days: This prevents water purification and can allow algae to regrow.
- Ignoring early signs of algae: Green water or sliminess should be treated immediately with shock and algaecide.
- Not maintaining the pump schedule: Consistent filtration is key to keeping the water clean.
Professional Tips for a Seamless Pool Opening
Here are expert tips from pool professionals and veteran pool owners:
- Keep a pool opening checklist to ensure nothing is missed during startup.
- Invest in high-quality test kits for accurate readings.
- Use a pool brush to scrub walls and steps during and after opening.
- Keep a log of chemical readings and treatment steps for future reference.
- Consider using enzyme-based clarifiers to break down oils and organics gently.
Conclusion: Make an Informed Decision Based on Your Pool’s Needs
Choosing between filter and recirculate when opening your pool isn’t a one-size-fits-all decision—it depends on the current condition of the water, the type of winter care your pool received, and the chemicals you’re using.
If your pool has visible contamination or needs chemical balancing, starting on recirculate can help distribute chemicals more effectively without straining the filter. However, once the initial phase is complete, always switch back to the filter mode to begin cleaning and clarifying the water.
By understanding the role of each setting and the needs of your specific pool, you can ensure that your startup goes smoothly, your water stays clear and safe, and your equipment lasts for years to come.
Final Thoughts: A Good Start Equals a Great Swimming Season
A well-planned pool opening not only makes pool maintenance easier but also improves the health and aesthetics of your pool water. Whether you choose to begin on filter or recirculate, the key is to have a purpose behind your choice and to follow up with proper testing, maintenance, and care.
Don’t rush the startup process—taking the time to evaluate your water chemistry, clean your equipment, and make strategic setting choices will save you time, money, and frustration down the line. With the right approach, your pool season can be off to the cleanest, safest, and most enjoyable start yet.
Remember, the goal is crystal-clear water, balanced chemistry, and a functional system. Your initial startup setting is just the beginning of achieving that.
What is the difference between the filter and recirculate settings on a pool pump?
The filter setting is the standard operating mode for your pool pump, where water is drawn from the pool, passed through the filter to remove debris, and then returned to the pool. This setting helps maintain water clarity and cleanliness by continuously cycling the water through the filtration system. On the other hand, the recirculate setting bypasses the filter media entirely, allowing water to flow directly back into the pool without being filtered.
Choosing between the two depends on what you’re aiming to achieve during pool maintenance or startup. The recirculate setting is often used when adding chemicals to the pool water, as it allows the chemicals to mix more evenly without passing through the filter, which could otherwise trap some chemicals before they disperse fully. However, it should not be used for extended periods because the water isn’t being cleaned of debris and contaminants.
When should I use the recirculate setting while opening my pool?
The recirculate setting is best suited for situations where you want to mix chemicals or water additives thoroughly throughout the pool without immediately filtering them out. This is particularly helpful after winterizing your pool or when you’re adjusting chemical balances during the startup process. Using recirculate in these cases ensures that treatment chemicals such as algaecides or clarifiers disperse more effectively without being trapped in the filter too soon.
However, using the recirculate setting should be short-term. While it helps evenly distribute chemicals, it does not clean the water. If left in this setting for too long, debris and particles will remain in the pool, leading to cloudy water and potential algae growth. Once the chemicals are fully dispersed, it’s advisable to switch back to the filter setting to begin cleaning the water properly.
Can I damage my filter by using the recirculate setting for too long?
Using the recirculate setting for an extended period does not directly damage the filter itself, but it bypasses the filtration process, which can lead to a buildup of contaminants in the pool water. While the filter is not actively being used in this mode, it remains in the system and may still be exposed to debris that could be stirred up during operation. Over time, this could indirectly impact the filter’s efficiency when you return to normal operation, especially if the pool has become cloudy or has high particulate levels.
To avoid putting extra strain on your filter later, it’s best to limit the use of recirculate to short durations for mixing chemicals or preparing the pool for filtration. Once you’ve achieved even chemical distribution, switching back to the filter setting ensures that your filtration system can properly clean the water and maintain optimal pool conditions.
Is it safe to open the pool using the filter setting right away?
Yes, using the filter setting right away during pool opening is generally safe and even recommended if the water appears visibly dirty or has debris from the winter cover. Starting on filter allows you to immediately begin removing suspended particles and improving water clarity. It’s particularly useful after removing a cover laden with leaves, dust, and other contaminants that fall into the pool during off-season.
However, if your priority is to mix initial doses of pool chemicals such as shock or algaecide, you may want to start on recirculate for about 30 minutes to an hour to ensure even distribution. After mixing chemicals thoroughly, you should switch back to filter mode to start cleaning the water and maintaining balance. Always check your filter pressure and ensure your system is primed correctly to avoid damaging the pump.
Will using the recirculate setting help clear a cloudy pool faster?
Using the recirculate setting will not help clear a cloudy pool because it bypasses the filter media, which is essential for removing fine particles that cause cloudiness. If your pool water is cloudy or green, starting on filter mode is critical to begin the process of circulating and filtering out debris, dirt, and microorganisms. In fact, using recirculate in this situation may prolong the time it takes to clear the water because impurities won’t be captured by the filter.
Instead of using recirculate, focus on brushing the pool walls and floor, adjusting chemical levels appropriately, and running the pump continuously on filter mode. Regularly backwashing or cleaning your filter will also enhance the water-clearing process. Once chemical levels stabilize and the water becomes visibly clear, maintenance can shift to normal filtration cycles.
How do I know which startup setting is best for my specific pool type?
The best setting for your pool during startup depends on your goals and the current state of the water. If the pool is already chemically balanced and the main purpose is even chemical distribution, recirculate is an effective choice. On the other hand, if the pool is covered with debris, green, or cloudy from winter, starting on the filter setting helps kickstart water purification immediately. Always assess your pool’s condition before selecting a startup setting.
Additionally, consider your filtration system type. For example, sand filters may perform differently than cartridge or DE filters during startup. Understanding your system and being aware of the manufacturer’s recommendations will help you make an informed decision. If you’re unsure, starting on filter is generally the safest option, as it supports healthy circulation and filtration right from the beginning of the pool season.
Can using the recirculate setting affect my pool’s chemical balance?
Using the recirculate setting itself does not alter your pool’s chemical balance, but it influences how chemicals disperse through the water. When on recirculate, the water is not filtered, which means chemicals are not removed or diluted as they might be during normal filtration. This can help achieve a more even chemical mix, especially after shocking the pool or adding algaecides. However, since filtration is paused, solids and debris remain suspended in the water, which could interfere with accurate chemical testing.
For best results, use the recirculate setting briefly to disperse chemicals, then switch to filter mode for effective cleaning and ongoing balance maintenance. Once the filtration system is active again, you can accurately monitor chemical levels and make adjustments as needed. Balancing chemical addition with effective filtration ensures a clean, safe, and well-maintained pool.