Pool maintenance is a critical aspect of owning a residential or commercial swimming pool. It’s not just about aesthetics; it’s also about safety, longevity of pool components, and creating a comfortable environment for swimmers. One of the basic—but often overlooked—decisions pool owners must make is whether to set their suction valves between the skimmer and the main drain.
The answer to “Should my pool be set to skimmer or main drain?” isn’t one-size-fits-all; instead, it depends on several key factors including the type of pool, climate, frequency of use, and your maintenance goals. This guide will help you understand the differences between the skimmer and main drain, when to use one over the other, and how balancing both can enhance pool maintenance efficiency.
Understanding Pool Suction: The Basics
To make an informed decision about your suction settings, it’s essential to first understand how your pool’s circulation and filtration system works.
What is the Skimmer?
The skimmer is an open box located in the wall of the pool, usually at the waterline. It is designed to remove floating debris like leaves, insects, and oils from the water’s surface. The skimmer also houses the skimmer basket and, in many pools, holds the floating pool cleaner hose or robotic cleaner intake.
By pulling water from the top layer, the skimmer helps to:
- Reduce visible debris
- Prevent algae growth by removing surface oils
- Maintain cleaner, clearer water
What is the Main Drain?
The main drain is located at the deepest point in the pool, typically at the bottom of the deep end. It is responsible for pulling water from the bottom of the pool, which helps in:
- Removing heavier debris like sand and sediment
- Encouraging water circulation and preventing stagnation
- Assisting in even distribution of chemicals in the water
Unlike the skimmer, which also serves filtration duties, the main drain generally doesn’t have a basket. This means anything entering the drain goes straight into the pump and filter system.
Skimmer vs. Main Drain: Where Do They Pull From?
Understanding where the skimmer and main drain draw water from provides crucial insight into when to prioritize one over the other.
Water Flow and Debris Collection
The skimmer draws water from the surface, where the majority of organic matter, such as leaves and pollen, floats. Surface water can also contain oils from sunscreen, body lotions, and other contaminants that can affect water balance and clarity.
The main drain, on the other hand, pulls from the bottom. In a typical pool, dirt, sand, and heavier debris settle here. Without proper main drain activity, sediment can build up and reduce filter efficiency.
Chemical Circulation
Pool water is chemically balanced and sanitized as it passes through the filtration system. Since the main drain pulls from the bottom, it helps recirculate the water from the deepest part of the pool, ensuring chemical distribution is not just at the surface.
The skimmer helps maintain chemical balance by bringing treated surface water through the system and recirculating it.
Energy Efficiency and Suction Balance
When both the skimmer and the main drain are partially open, the pool pump can operate more efficiently. This is because balancing the suction points reduces pressure and prevents the pump from working too hard. If only one valve is open (e.g., just the skimmer), the pump may experience strain, increasing wear and energy consumption.
When to Prioritize the Skimmer
Depending on the environmental conditions and usage patterns of your pool, you may want to prioritize the skimmer.
During Pool Opening Season
When you open your pool at the start of the season, especially after winter, a significant amount of debris tends to accumulate on the surface. In this case, running the pump with the skimmer valve fully open (or mostly open) helps remove this floating matter more quickly.
This can be particularly helpful in early spring when pollen and early-season foliage are prevalent.
Heavy Surface Debris Days
If your pool is surrounded by trees, experiences frequent pollen, or if there’s a lot of wind carrying leaves and other debris across the surface, setting more suction to the skimmer side is crucial.
This can prevent:
- Unclean water with an oily surface film
- Increased chlorine demands to oxidize surface contaminants
- Blocked filtration caused by organic matter
When Using a Floating Pool Cleaner
Many automatic pool cleaners, especially floating types, operate by being connected directly to the skimmer. In these situations, you may want to reduce the main drain suction to avoid interrupting the cleaner’s water flow or performance.
When to Prioritize the Main Drain
There are certain scenarios when relying more heavily on the main drain makes more sense.
If You’re Having Issues with Pool Bottom Debris
Heavy sediment, sand, or dirt buildup on the pool floor can be a challenge. If the filtration system is over-prioritizing the surface water, it may leave heavier debris undisturbed.
Opening up the main drain valve more fully can help draw water (and debris) from the bottom more effectively and assist in a thorough cleaning.
During Algae Outbreaks or Pool Shocking
During or after shocking your pool—especially after a green or cloudy water incident—it’s important to engage all water circulation paths. Algae and contaminants often settle on the bottom of the pool, making the main drain an essential tool in this process.
Using both suction lines at once (or increasing main drain intake temporarily) can speed up overall water turnover, increasing the effectiveness of the shock treatment.
When the Skimmer Baskets Are Clogged
If your skimmer baskets are full and you’re not able to clean them regularly, the suction power to the pump drops, and your filtration becomes inefficient. Temporarily increasing main drain suction can help maintain filtration performance, even if the skimmer line is compromised.
Why You Should Often Use Both Together
While choosing between skimmer and main drain is a valid strategy depending on conditions, most experts recommend running both suction sources together for optimal filtration, especially during routine weekly maintenance.
Balanced Water Turnover
A balanced valve setting—typically 75% skimmer and 25% main drain or vice versa—ensures the most effective water turnover. This helps maintain cleanliness throughout all layers of the pool water and prevents stagnation.
Efficient Chemical Mixing
When both lines are active, you promote even chemical distribution. If all the suction came from the skimmer, chemicals may not fully circulate through the entire water body, particularly the bottom.
Preventing Pump Issues
Running only one suction line (especially main drain alone) can cause issues with your pump like:
- Airlocks
- Overheating from increased strain
- Reduced flow efficiency
Using both suction points helps balance flow and maintain optimal pump performance.
Adjusting Valve Settings: A Practical Guide
Properly adjusting the suction line valves ensures you’re optimizing your filtration system.
Understanding Your Multiport Valve or Diverter Valves
Most pools use multiport valves or individual diverter valves for the suction lines (sometimes labeled as skimmer and main drain). These can be manually adjusted to allow more or less flow from each suction point.
Recommended Settings for Different Scenarios
Here’s a summary of valve settings for different maintenance tasks:
| Pool Condition | Recommended Skimmer Valve Setting | Recommended Main Drain Valve Setting |
|---|---|---|
| After Pool Opening | 70–90% | 10–30% |
| Intense Pollen Season | 80% | 20% |
| Bottom Sediment Problem | 30–50% | 50–70% |
| Routine Filtration | 60–70% | 30–40% |
| Shock Treatment Week | 50% | 50% |
How Often Should You Adjust Suction Valves?
Valve adjustments generally don’t need to happen daily. However, you should review and adjust when there is a change in pool conditions, such as:
- Increased debris from a storm
- Refilling after drain
- Chlorine level imbalances
- Unusual water cloudiness
Readjusting your suction points once every couple of weeks based on seasonal conditions will help keep your maintenance efficient.
Safety Considerations: Main Drain Hazards and Best Practices
While effective, main drains also come with certain safety concerns, especially in residential and community pools.
Anti-Entrapment Regulations
Older pools with a single main drain are at higher risk for drain entrapment, which is why the VGSS (Virginia Graeme Baker Pool and Spa Safety Act) mandates pools to be equipped with anti-entrapment drain covers and multiple suction outlets.
Always ensure your main drain complies with current safety codes. If you’re using a single main drain with high suction, even unintentionally (by closing the skimmer line), you risk entrapment hazards for bathers.
Running on Main Drain Alone
While possible in emergencies or during specific maintenance tasks, running your pool filtration only through the main drain is not recommended for long-term periods. Doing so can:
- Decrease the turnover of surface water
- Increase energy usage due to flow inefficiency
- Create hazardous traction conditions for swimmers
It’s best to always have some level of skimmer input.
Skimmer Optimization Tips
To get the most out of your skimmer and improve your pool’s cleanliness and filtration:
Keep the Skimmer Baskets Clean
Empty and rinse the baskets at least twice a week during the swimming season, more often if your pool is surrounded by trees or shrubs. A clogged basket can reduce flow efficiency and strain the pump.
Use Skimmer Socks
Skimmer socks are mesh inserts that go into the skimmer basket and trap finer particles, oils, and lint. These can prolong the life of your pump and reduce filter work.
Regular Skimmer Line Inspection
Ensure that the skimmer suction line is free of obstructions, cracks, or debris buildup. An improperly sealed skimmer seal can allow air to enter the pump, reducing efficiency or causing performance issues.
Conclusion: Finding the Best Setup for Your Pool
So, should your pool be set to skimmer or main drain? The short answer is: both, most of the time. However, depending on your specific pool type, environmental conditions, and maintenance needs, you may want to tilt the balance one way or the other.
By understanding the unique role each suction line plays and making small adjustments based on real-world conditions, you’ll enjoy clear water, efficient filtration, prolonged equipment life, and reduced chemical costs.
Final Recommendations
- Use both skimmer and main drain for daily filtration.
- Allow for slight adjustment depending on debris levels and season.
- Never fully close the skimmer unless under emergency circumstances.
- Inspect and clean skimmer baskets and drains regularly.
For optimal results, track your settings over a few seasons and adjust based on your most recurring pool challenges. With this strategy, your pool can maintain a level of cleanliness and circulation that keeps your family safe and happy all year round.
What is the difference between a pool skimmer and a main drain?
The pool skimmer and main drain serve distinct but complementary roles in maintaining proper water circulation and cleanliness. The skimmer is located near the water’s surface and primarily removes floating debris such as leaves, insects, and oils before they sink to the bottom. It also draws water from the top layer, which helps in filtering out contaminants and maintaining chemical balance.
Conversely, the main drain is located at the bottom of the pool and is responsible for drawing in water from the lower levels. This ensures that the entire volume of water circulates through the filtration system, preventing stagnant zones and promoting even temperature and chemical distribution. While the skimmer helps with surface-level maintenance, the main drain plays a key role in overall water turnover and system efficiency.
Should I use only the skimmer, only the main drain, or both?
The ideal setup depends on various factors, including pool usage, season, and water conditions. Using only the skimmer may be sufficient under normal conditions, especially when the pool is exposed to a lot of surface debris. However, relying solely on the skimmer can lead to poor circulation at the pool bottom, which can result in algae growth or cloudy water.
On the other hand, using only the main drain is generally not recommended because it misses the opportunity to remove floating debris and oils. For most pool owners, using both the skimmer and the main drain in a balanced manner ensures comprehensive circulation and filtration. Valves can be adjusted seasonally or based on specific needs, but a combination approach typically delivers the best results for water clarity and system performance.
How does using the skimmer or main drain affect water chemistry?
Proper water circulation through both the skimmer and main drain significantly influences water chemistry balance. Skimmers help remove surface contaminants such as oils and organic materials that can deplete chlorine levels and cause foam or scum lines. By eliminating these early, they reduce the chemical demand and help maintain sanitizer efficiency.
Main drains, by pulling water from the bottom, prevent chemical stratification and ensure even distribution of sanitizers throughout the pool. This helps maintain consistent pH and chlorine levels, which are crucial for sanitation and swimmer comfort. Neglecting either component can lead to uneven chemical distribution and potential problem areas in the pool, such as algae pockets or cloudy water.
Can the choice between skimmer and main drain affect energy efficiency?
Yes, the configuration of your skimmer and main drain settings can influence the energy efficiency of your pool system. If too much suction is directed toward the main drain, the pump may have to work harder to draw water from the bottom, especially if the drain’s flow is restricted or if the pump is not optimized for this setup. This can increase energy consumption and wear on the pump motor.
Adjusting the balance between skimmer and main drain valves properly allows the pump to operate at an optimal flow rate, reducing strain and power use. Additionally, when the system runs more efficiently, it can maintain water quality with fewer chemical adjustments and filter run times, indirectly contributing to lower operational costs. A balanced approach using both inlets is generally best for energy efficiency.
How does debris type determine whether to use the skimmer or main drain?
The type of debris your pool collects plays a significant role in determining whether you should focus more suction on the skimmer or the main drain. For instance, if your pool is surrounded by trees and receives a lot of floating debris such as leaves, pollen, or petals, increasing the skimmer’s intake will help capture these particles before they sink and decompose in the pool.
In contrast, if the pool floor tends to accumulate fine sediment or algae growth, especially after a heavy rain or during algae season, more suction from the main drain can help circulate that water through the filter for better cleaning. A combination of both inlets is often best, allowing for the efficient capture of both floating and submerged debris, ensuring a balanced and clean system.
What are the safety concerns associated with main drain usage?
Main drain safety is a serious consideration, especially in older pools that may not have updated drain covers or dual-drain systems. Single main drains pose a risk of entrapment if the cover becomes loose or damaged. This can lead to dangerous situations where a swimmer’s body, hair, or clothing gets trapped, potentially resulting in serious injury or drowning.
To mitigate these risks, the U.S. Consumer Product Safety Commission requires compliance with the Virginia Graeme Baker Pool and Spa Safety Act (VGB Act), which mandates the use of anti-entrapment drain covers. If your pool has a single main drain, it’s recommended to install a secondary drain or retrofit with VGB-compliant covers. Additionally, regularly inspecting the drain covers and ensuring they are secure is vital for safe operation.
How often should I adjust the skimmer and main drain settings?
The frequency of adjusting skimmer and main drain settings depends largely on seasonal factors, pool conditions, and how often the pool is used. During the swimming season, especially in spring and fall when debris is more prevalent, it may be necessary to adjust valve settings weekly based on the level of floating or settled debris. Frequent rains, high winds, or nearby vegetation can also necessitate more frequent adjustments.
If your pool has a consistent usage pattern and is well-maintained, adjusting the settings every few weeks or monthly may suffice. However, monitoring water clarity and filter pressure can guide necessary changes. Regular adjustments help ensure optimal water circulation and filtration, reducing maintenance issues and chemical demand in the long run while maintaining a clean and safe swimming environment.