Maintaining an inground pool involves a variety of tasks, from regular cleaning to balancing chemical levels. One of the more debated topics among pool owners is how often they should drain the pool. Many assume that periodic draining is a necessary part of maintenance, but the truth isn’t always so clear-cut.
In this comprehensive guide, we’ll explore everything you need to know about draining your inground pool. We’ll break down the reasons you might consider draining it, how often that’s actually necessary, what happens during the process, and best practices for doing it safely. By the end, you’ll have a clear understanding of when—and why—you should drain your pool, and when it’s better to leave the water in place.
Why Draining Your Pool Might Be Necessary
Before discussing frequency, it’s important to understand why one would even consider draining an inground pool. There are several valid reasons that might prompt you to let the water out:
1. High Total Dissolved Solids (TDS)
Over time, pool water accumulates minerals, chemicals, and other residues. This buildup increases the Total Dissolved Solids (TDS) level. When TDS levels become too high, the effectiveness of sanitizers like chlorine drops significantly. High TDS can also cause water to become cloudy or irritating to swimmers.
Draining is typically considered when TDS levels surpass 1,500 ppm, though this can vary depending on the type of system and water source.
2. Staining and Scale Buildup
Some pool surfaces, particularly plaster or exposed aggregate finishes, are prone to staining and scaling. If your pool’s water has high calcium hardness or pH levels that fluctuate often, it can leave behind mineral deposits that dull the finish and trap algae. Regular acid washing or manual scrubbing can help, but in severe cases, draining the pool may be the only solution.
3. Major Renovations or Repairs
Draining is necessary when you’re undergoing a pool renovation, such as replastering, resurfacing tile, fixing cracks, or replacing a broken main drain. These types of structural or aesthetic updates almost always require the pool to be empty and dry.
4. Severe Algae Infestation or Poor Water Balance
If your pool has suffered a persistent algae problem that chemicals alone can’t correct, completely draining and refilling could provide a “fresh start.” Similarly, chronic imbalances in pH, alkalinity, or calcium hardness may eventually lead to draining the water to reset its chemical foundation.
How Often Is Too Often?
The general rule of thumb for draining an inground pool is every 3 to 5 years. This timeline allows pool water to be updated before chemical buildup becomes problematic while also ensuring you don’t unnecessarily subject the structure and equipment to wear through repeated dewatering.
Daily Use vs. Seasonal Use
In regions with long swimming seasons, a pool could see heavy use for six months or more. This frequent usage increases contaminant buildup, requiring more rigorous water maintenance. In these cases, even if you’re diligent with chemistry, the water may still need to be refreshed every 3 years on the shorter end of the timeline.
For pools used seasonally—only in spring and summer—the cycle can stretch closer to five years unless the chemical demand increases dramatically due to poor maintenance or environmental factors like vegetation, dust, or hard water.
Climate and Environmental Factors
Your local environment and water supply play a key role in how quickly water deteriorates. In hard water areas, mineral deposits can accumulate faster, forcing earlier drain cycles. For those in dry or dusty regions, particulate matter and organic growths may mean more frequent draining to restore clarity and surface aesthetics.
Chemical Maintenance Practices
A well-maintained pool is likely to sustain quality water longer than a pool with inconsistent maintenance. If an owner properly balances pH, alkalinity, chlorine, and other chemical levels, and uses technologies like saltwater chlorinators or phosphate removers, draining can safely be extended closer to the five-year mark.
Signs Your Pool Water Needs Draining
Knowing when to drain requires more than just keeping a calendar. Be alert for these key indicators:
1. Persistent Cloudiness or Irritation
Chronic murkiness even after chemical correction can point to high TDS. Swimmers might also complain of dry skin or burning eyes even when chemical levels appear to be within range.
2. Failure to Balance Water Chemistry
If you’re constantly adjusting for high total alkalinity or calcium hardness and nothing seems to hold, it’s time to consider draining and starting fresh. When the chemical load is too high, no amount of adjustment will stabilize the water effectively.
3. Plaster Degradation
Cracks in the plaster, flaking, or uneven textures can indicate an aging surface that’s reacting poorly to poor water chemistry. Acid washing or draining for resurfacing might be the next logical step.
4. Visible Scale Formation
Hard, chalky buildup along tile, skimmer faces, or inside pool returns suggests calcium scaling. While minor scale can be addressed with chemical treatments or manual scrubbing, persistent issues may necessitate full draining.
5. Pool Filter Efficiency Declines
If your pool continues to hold particles even after consistent filtration and cleaning, or if your filter struggles to maintain flow rates due to scale or clogging, high TDS could be gumming up your system—and draining may be the solution.
What Happens During Pool Draining?
Draining an inground pool isn’t as simple as just turning on a pump and letting the water flow out. If not done correctly, this process can cause costly structural damage.
Professional vs DIY Approach
While homeowners skilled in pool mechanics might attempt a draining, it’s highly advisable to leave it to professionals. Most pool contractors or service companies have experience draining pools safely, which is critical to preserving the structure and integrity of your pool.
Dewatering Steps
- Chemical levels check: Before draining, ensure that chlorine and other chemicals are neutralized to environmentally acceptable standards to avoid harming your plumbing system or local waterways.
- Equipment shut off: Disconnect and power off pool pumps, heaters, chlorinators, and any automation systems.
- Pump and remove water: Using a submersible pump or city water truck, the water is extracted carefully.
- Monitor for hydrostatic pressure: Some pools have a hydrostatic relief valve that allows groundwater pressure to be released. If not, a professional must monitor the structure for signs of upheaval or damage.
The Risk of Hydrostatic Uplift
One of the most significant dangers when draining an inground pool is hydrostatic uplift. If the water table surrounding the pool is higher than the water level inside the pool, the groundwater pressure can push the empty pool upward—a major concern for concrete or plastered pools. This issue is less common with fiberglass and vinyl-lined pools, though precautions still apply.
To reduce this risk, many pools are equipped with a hydrostatic valve located near the main drain. When drained, this valve opens to allow groundwater in to balance pressure and prevent uplifting. However, not all pools have such systems, and in some areas, the water table is high regardless, so caution and professional oversight are essential.
The Cost of Draining a Pool
The cost of draining an inground pool can vary depending on several factors, including pool size, structure type, location, and the presence of a dewatering system. Generally, you’re looking at:
- Small pools (10,000–15,000 gallons): $300–$600
- Medium pools (15,000–25,000 gallons): $600–$1,200
- Large pools (25,000+ gallons): $1,000–$2,500 or more, particularly if structural checks and hydrostatic controls are required
These cost ranges include the physical act of draining, water disposal coordination (if required), and professional guidance. If pool resurfacing or repairs need to be scheduled as part of this process, total project expenses can climb significantly.
Best Practices When Draining Your Pool
To prevent costly repairs and extend the life of your pool, follow these best practices when you decide to drain it:
1. Check Local Regulations
Many municipalities regulate where and how pool water can be disposed of. High chlorine content requires dechlorination before release into sewer systems or storm drains.
2. Use the Right Equipment
High volume pumps are essential for efficient draining. Also, using sump pumps from the pool’s deep end can expedite the process—but always monitor the surrounding soil and pool structure.
3. Never Leave It Empty for Long
A drained pool should be refilled as soon as possible—within 24–48 hours in most cases. Leaving it empty for any longer—especially during hot or rainy weather—can compromise water balance features and increase the risk of structural damage.
4. Clean and Inspect the Shell
With the water removed, it’s the ideal time to inspect the shell for cracks, leaks, or wear. Minor scum buildup or plaster etching can be cleaned. If significant repair work is needed, address this before refilling.
5. Rebalance the Water After Refilling
Using fresh water from the city supply is the ideal solution—though well water users should have their water tested first for hardness and mineral content. Once refilled, rebalancing the pool water is crucial before allowing anyone to swim.
Alternatives to Draining the Pool
Before you resort to draining, consider other techniques that can help manage water quality and chemical buildup:
1. Partial Drain and Refill
If your water is becoming saturated but not yet unmanageable, consider draining a portion—say 20–30%—of the pool instead of the full volume. This lowers TDS and chemical concentrations while reducing overall cost and risk.
2. Use a TDS Reducer
Some water treatment companies offer specialized TDS reduction services using reverse osmosis technology. This method can filter the water on-site, reducing mineral and chemical content without full draining. While more expensive upfront, it may actually offer a longer interval between full drain cycles.
3. Advanced Sanitization Methods
Incorporate advanced systems like mineral purifiers, UV clarifiers, or ionizers to reduce chemical dependency and slow the buildup of byproducts in your pool water.
Real-Life Examples: When To Drain—and When Not To
Let’s consider two real-life scenarios:
Example 1: A Concrete Inground Pool in Arizona
A homeowner in sunny Phoenix has a 20,000-gallon concrete inground pool. The water hardness in the city is high, and evaporation is significant in summer. They’ve maintained the pool well but used mostly chlorine tablets and shock. Their water tests reveal:
– TDS: 2,000 ppm
– pH: consistently high
– Hardness: 350 ppm
– Plaster is flaking and feels gritty
Draining would make sense here—this pool has reached the five-year mark and is showing classic signs of over-mineralization. Refilling with softer water will prevent continued damage to the surface and reduce chemical usage moving forward.
Example 2: A Fiberglass Pool in Florida
A similar-sized fiberglass inground pool in humid, subtropical Florida has a pH that fluctuates but balances within a week after adjustment. The owner has a salt chlorine generator and diligently maintains all water levels. Despite heavy swimmer loads, the pool looks clear, no scale is evident, and a water test shows TDS at just 900 ppm.
In this case, draining isn’t currently necessary. While it should be watched closely, another 1–2 years before draining seems acceptable.
Conclusion: Make Informed Decisions About Draining
Draining your inground pool doesn’t have to be a common chore, but it can become a necessary one. Plan to fully drain the pool every 3–5 years unless signs of water saturation or structural damage demand earlier intervention.
Understanding the science behind TDS, the risks involved in the draining process, and effective alternatives can save you thousands of dollars in damage—and extend the life of your cherished backyard oasis.
If you’re ever unsure whether to drain your pool, consult with a professional pool technician or service provider. They can test your water parameters, inspect the pool structure, and determine the most cost-effective, safe course of action for you.
Maintaining clean water doesn’t always mean emptying it. Sometimes, the smartest strategy is better chemical management and upgrading your pool system instead of hitting the reset button. But when the signs do tell you it’s time—act wisely and carefully.
How often should you drain an inground pool?
Draining an inground pool is not something that needs to be done frequently. As a general guideline, you should only drain your pool every 3 to 5 years. This timeframe allows the water chemistry to remain balanced and prevents unnecessary wear on the pool structure. However, certain situations like high total dissolved solids (TDS), staining, or significant algae buildup might require earlier draining.
If you’re dealing with routine maintenance or minor water chemistry issues, there are often ways to correct those problems without full draining. Partial draining combined with dilution using fresh water can be effective. Always consult with a pool professional before draining to ensure it’s necessary and to avoid damage to your pool surface or equipment.
What are the risks of draining an inground pool too often?
Frequent draining can harm both the structure and the longevity of your inground pool. Pools are designed to have water in them, which helps maintain balance and structural integrity. Draining too often can cause stress on the pool shell, especially in areas with high groundwater levels, which might lead to shifting or cracking.
In addition to structural risks, draining too often can cause unnecessary wear on filtration systems, plumbing, and interior finishes. It also increases water and chemical usage, leading to higher costs and environmental impact. Proper maintenance is usually a better solution than regular draining for most pool-related problems.
When is it necessary to drain an inground pool?
You should consider draining your inground pool when the water becomes unsalvageable due to severe staining, high TDS levels, or persistent algae infestations that resist conventional treatments. Draining is also necessary during major renovations, repairs, or when winterizing the pool in freezing climates.
In some cases, changing the type of sanitization system (e.g., from traditional chlorine to a saltwater system) might also require new water with the correct chemical base. However, always verify with a pool expert to confirm if draining is essential or if treatments or partial water replacement would suffice.
Can you drain part of your inground pool instead of completely emptying it?
Yes, in many cases partial draining is sufficient and preferred over completely emptying an inground pool. Lowering the water level to just below the tile line or to the midpoint of the skimmer allows for maintenance tasks like acid washing or treating chemical imbalances without exposing the entire structure.
Partial draining also helps maintain structural integrity, especially in environments where groundwater pressure could damage an empty pool. Additionally, this method conserves water and reduces chemical costs for refilling. It is an effective way to deal with moderate issues while avoiding the risks and expense associated with full draining.
What should you consider before draining an inground pool?
Before draining your inground pool, it’s important to evaluate local groundwater conditions. In areas with a high water table, hydrostatic pressure from groundwater can cause an empty pool to float out of the ground. Pool professionals often recommend keeping the pool full or timing draining during dry seasons when the risk is lower.
Also consider local water restrictions and environmental impacts, as draining a pool can use a large amount of water. Be mindful of chemical levels in the water—chlorine and pH must be neutralized before discharging water into the sewer system or onto the ground. A licensed pool technician can help ensure the process is done legally and safely.
How long does it take to drain an inground pool?
The time required to drain an inground pool depends on its size and the method used. Using a standard submersible pump, it can take anywhere from 8 to 14 hours for an average-sized pool. Larger pools or using a smaller pump can extend this time significantly. If you’re using a pool’s built-in drainage system or a professional service, it may be faster or slower depending on equipment capacity.
It’s important to closely monitor the draining process to avoid unexpected issues such as clogged lines or damage to the pool surface. During the process, ensure that skimmer and return lines are closed or properly winterized to prevent damage. Draining should ideally be done under the guidance of a professional or someone experienced in pool maintenance.
What steps should you take after draining your inground pool?
After draining your inground pool, the next steps depend on the reason for draining. If you’re doing maintenance or repairs, inspect the pool for cracks, leaks, or worn tiles and address any issues before refilling. Cleaning the surface and applying any necessary treatments, such as plastering or resurfacing, should be done before adding water.
It’s also essential to refill the pool promptly, especially if you live in an area with high groundwater levels. Filling too slowly or waiting too long can expose the pool to damage. After refilling, rebalance the water chemistry carefully before restarting equipment and adding sanitizer to maintain proper pool function.