When a pool has been sitting unused for weeks or even months, it can quickly become a breeding ground for algae, debris, and unbalanced chemicals. Whether this happened due to a busy schedule, seasonal changes, or a simple oversight, a neglected pool may seem daunting to clean. But with the right guidance and a methodical approach, you can bring your pool back to its sparkling best — and safely enjoy it for years to come.
This comprehensive article will walk you through every essential step of cleaning a pool that has been sitting, including proper water chemistry balancing, manual cleaning methods, and maintenance tips to prevent future issues. Let’s dive in!
Step 1: Assess the Pool Condition and Remove Surface Debris
Before diving into the cleaning process, it’s important to visually evaluate the pool’s current state. Note the water clarity, presence of algae, any floating debris, and possible damage to the pool surface or equipment.
Begin with Skimming the Surface
Use a skimmer net to manually remove leaves, twigs, and other floating debris. This helps reduce the organic load in the pool and makes it easier for chemicals and filtration to work effectively.
Empty the Skimmer Baskets and Pump Basket
After skimming, ensure the skimmer and pump baskets are free of accumulated debris. A clogged basket can impede water flow and filtration performance.
Inspect the Filter
Depending on the type of filter (sand, cartridge, or diatomaceous earth), it might need cleaning or inspection before proceeding. A clogged or dirty filter won’t effectively support the cleaning process.
Step 2: Drain and Refill if Necessary
If the pool water is black, heavily stained, or contains high levels of contaminants, it may not be cost-effective to chemically treat the existing water. Draining should be considered only when:
- There’s significant algae buildup that chemical treatments can’t easily correct
- The water is extremely cloudy or has an unpleasant odor
- There’s an excessive buildup of metals or other contaminants
Check Local Regulations Before Draining
In some areas, local codes or environmental laws regulate how pool water should be discharged to prevent damage to sewers, plants, or natural waterways. Consult your local municipality before emptying the pool.
Use a Submersible Pump for Draining
If draining is necessary, use a submersible pump or rent a de-watering pump. Ensure proper hose placement for directing water away from property or landscape damage.
Step 3: Shock the Pool and Balance the Water Chemistry
Even with clean-looking water, stagnant pools lose chemical stabilization over time. Pool shocking involves adding a large dose of chlorine or non-chlorine oxidizer to eliminate bacteria and organic contaminants.
Test the Water with a Pool Test Kit or Strips
Before shocking, use a reliable test kit to measure:
- Chlorine levels
- pH levels
- Total alkalinity
- Calcium hardness
- Cyanuric Acid (CYA)
These readings will guide you in properly balancing the water after shocking.
Choose the Right Pool Shock
There are two primary types of shock:
- Chlorine-based Shock – Most common and effective. Use calcium hypochlorite or sodium dichlor. Ensure proper dissolution and never add shock directly to the skimmer.
- Non-Chlorine Shock – Ideal for swimming quickly after treatment, usually with potassium monopersulfate (MPS). Less effective for severe algae breakouts.
Important Tips:
- Test and adjust pH before shocking.
- Shock the pool in the evening to prevent sunlight degradation of chlorine.
- Wait 8–12 hours before swimming or retesting water quality.
Step 4: Run the Filter System Continuously
To circulate the water and clear out the dead algae and particles after shocking, the filtration system must run constantly for at least 24–48 hours, if not longer. This is crucial to restore water clarity.
Backwash or Clean the Filter As Needed
Monitor the filter pressure gauge. If it’s significantly higher than normal, it’s time to backwash (sand or DE filters) or clean the cartridge. Dirty filters can re-contaminate the pool water.
Use Clarifiers or Flocculants
When the water remains cloudy, these products help bond tiny particles so the filter can capture them more efficiently. Depending on your setup:
- Water Clarifiers are ideal for cartridge and DE filters.
- Flocculants (like alum) are used with sand filters because they sink particles to the bottom for vacuuming.
Step 5: Brush and Vacuum the Pool Floor and Walls
Once the filter system has been running and the chlorine levels are stabilized, it’s time to manually scrub algae and debris off the pool surfaces.
Use the Right Brush
Choosing the correct brush type is important depending on your pool surface:
| Pool Surface | Recommended Brush |
|---|---|
| Concrete (Plaster) | Stiff nylon or steel bristles |
| Vinyl Liner | Soft nylon bristles |
| Fiberglass | Soft to medium bristles |
Vacuum with a Pool Vacuum and Hose
It’s best to set the filter to the “waste” setting if your valve allows it. Vacuum up large volumes of dead algae or sediment directly to waste instead of through the filter to avoid clogging.
If not, vacuum on the “filter” setting and combine with frequent backwashing. For pools with high debris, a robotic pool cleaner can greatly speed this process.
Step 6: Re-Balance the Water Chemistry
Once the water clears and the pool is mostly clean, it’s time for a final round of water chemistry testing and adjustment.
Adjust pH to 7.2–7.6
A balanced pH ensures chlorine works effectively and makes swimming comfortable. Use pH increasers or decreasers as necessary.
Check Total Alkalinity (80–120 ppm)
Balancing alkalinity before adjusting pH yields more stable results. Sodium bicarbonate is commonly used to raise alkalinity.
Maintain Calcium Hardness (200–400 ppm)
Too low calcium can cause plaster damage; too high causes scaling. Add calcium chloride if levels fall below 200 ppm.
Set Cyanuric Acid Levels (30–50 ppm)
CYA (stabilizer) prolongs chlorine’s effectiveness under sunlight. Add stabilizer carefully to avoid going above 100 ppm, which can lead to “chlorine lock.”
Step 7: Inspect Pool Equipment and Make Necessary Repairs
With the water clean and balanced, it’s the perfect time to check all your pool system components:
Check the Pump and Motor
Ensure the pump is running properly and the motor isn’t making unusual noises. Tighten or replace leaking fittings.
Inspect the Return Jets and Skimmers
Make sure jets are not clogged and skimmers have no cracks or blockages. Proper water circulation starts here.
Test the Pool Heater, if Applicable
Run the heater through its basic cycle to check ignition and temperature responses. Contact a technician if problems arise.
Verify Automation (Pool Cleaner, Valves, Chlorinator)
If your pool setup includes automation or a saltwater system, test these after cleaning for functionality.
Step 8: Maintain Your Cleaned Pool to Prevent Future Neglect
Cleaning a long-stagnant pool is time-consuming, but the same steps can serve as a foundation for effective maintenance.
Skim and Brush Weekly
Consistent manual cleaning can drastically slow algae growth and prevent larger interventions.
Test and Adjust Chemicals Weekly
Maintaining balanced chemistry is key to keeping pool water clear and swimmer-safe.
Backwash or Clean Filters Monthly
Depending on environmental conditions, your filter may need cleaning every few weeks or at least once a month.
Use a Pool Cover
To reduce evaporation, heating costs, and debris accumulation, invest in a solid pool cover. This is especially valuable during off-season or prolonged neglect periods.
Tips for Faster and More Effective Cleaning
To optimize the cleaning process even further, try these professional-level practices:
Hire a Pool Professional for Deep Cleaning
If your pool has excessive staining, a professional pool company can offer pool acid washing, deep vacuuming, or stain removal services safely and more efficiently.
Use Pool Water Test Kits Instead of Test Strips
Test strips are convenient, but a liquid DPD or digital water-testing kit gives more accurate readings — crucial when rebalancing after a deep clean.
Invest in a Good Robotic Cleaner
For regular maintenance or deep cleaning, robotic cleaners are fast, energy-efficient, and operate independently of your filtration system.
Apply Pool Algaecide Weekly as Preventative Support
Weekly addition of a metallic or quaternary algaecide can deter algae regrowth — especially helpful for pools that are inconsistently maintained.
Conclusion
Cleaning a pool that has been sitting unused can seem like a major task, but with this thorough approach, it’s possible to revive your pool to a gleaming, safe, and enjoyable state. From initial debris removal to chemical balancing and equipment checks, following this detailed guide will bring your swimming sanctuary back to its best condition.
Remember, consistent maintenance is the key to avoiding months of neglect in the future. Invest in the right tools, stay on a chemical testing schedule, and consider automation or help from professionals when necessary. With these efforts, your pool will always be ready for a refreshing dip!
By using this guide, you’ll not only save money on repairs but also preserve the life and appearance of your investment. So, roll up those sleeves, grab your tools, and get ready to enjoy a sparkling clean pool all season long.
How long does it take to clean a pool that’s been sitting unused?
Cleaning a long-neglected pool can take anywhere from a few hours to several days, depending on how long it’s been unused and the condition it’s in. If the pool has been sitting for just a few weeks, you may be able to clean and balance the water in a day. However, for pools that have turned green or developed algae, mold, and debris buildup over months or seasons, the process requires more intensive cleaning, filtration, and chemical balancing, which may extend over multiple days.
Timelines are also affected by the efficiency of equipment such as the filter and pump. If your filtration system is working properly, circulation and water clarity will improve more quickly. During the cleaning process, you may need to backwash filters frequently and even replace filter media if necessary. Patience and consistency are key, especially when it comes to restoring proper chemical levels to ensure safe and clear swimming conditions.
Can I use household bleach to clean my pool?
While household bleach can technically disinfect water because it contains chlorine, it’s not the ideal substitute for pool-grade chlorine. Pool chlorine is specifically formulated to maintain safe and balanced water chemistry and is available in stabilized forms that protect against sunlight degradation. Household bleach is often lower in strength (typically around 5-8% sodium hypochlorite) and does not contain stabilizers or other additives that help maintain chlorine’s effectiveness in a pool.
If you’re in a dire situation and only have access to bleach, you can use it temporarily to shock the water. However, you must choose unscented bleach without additives like dyes or thickeners. Accurate calculation of the required dosage is crucial to avoid underchlorination or dangerously high chlorine levels. After using bleach, it’s important to follow up with proper pool chemicals to maintain the correct pH, alkalinity, and chlorine stabilization over time.
Is it necessary to drain the pool completely before cleaning?
Draining a pool completely is generally not necessary unless the water is heavily contaminated with debris, algae, or has an extremely high concentration of dissolved solids. In most cases, you can clean and restore your pool without draining, especially if the structure is in good condition and only requires filtration, brushing, and chemical balancing. Draining a pool can actually be risky, as emptying it may lead to structural damage due to groundwater pressure pushing the pool upward.
If the water is very cloudy or discolored but the pool structure remains intact, it’s best to keep the water and start by shocking it with chlorine, brushing the surfaces, and running the filter continuously to restore clarity. Partially draining the pool can help in situations where total dissolved solids (TDS) or metals (such as iron or copper) are too high, but a professional water test can determine whether that step is truly needed.
How often should I clean and maintain my pool after reviving it?
After successfully cleaning and restoring your pool, regular maintenance is essential to keep it in optimal condition. At minimum, you should test your water chemistry two to three times a week and adjust chemical levels accordingly. Daily skimming, weekly brushing of walls and floors, and routine vacuuming will help prevent debris buildup and algae growth. Your filter should run for 8–12 hours per day during warmer months to ensure proper circulation and filtration.
Seasonal changes, heavy usage, and weather conditions will impact how frequently you need to clean your pool. For instance, after rainstorms or during the fall season when leaves are more prevalent, extra skimming and vacuuming are typically necessary. Maintaining a consistent schedule after the initial clean-up will not only save you time in the long run but also extend the life of your pool and equipment, ensuring a healthy swimming environment year-round.
What type of filter should I use during the cleaning process?
The type of filter you should use during the cleaning process depends on what kind of filtration system your pool already has—sand, cartridge, or diatomaceous earth (DE). For revitalizing a stagnant pool, all three can work, but each requires specific attention. Sand filters may need frequent backwashing, cartridge filters require thorough cleaning or replacement if they’re too clogged, and DE filters must be broken down and recharged with fresh DE powder after cleaning out the grids.
Regardless of the type, it’s important to ensure your filter is functioning properly to clear out debris and contaminants efficiently. If your system has been dormant, inspecting the filter for damage or wear before starting the cleaning process is essential. Once the pool is clear, you may clean or replace the filter media as needed to maintain optimal filter performance during regular use.
Do I need to brush the pool even if I have an automatic cleaner?
Yes, brushing the pool surfaces is an important step even if you have an automatic cleaner. An automatic cleaner typically works best on a pool that’s already in relatively good condition, but it may not be effective immediately on a neglected pool with thick algae or biofilm buildup. Brushing loosens debris, algae, and contaminants that stick to the walls and floor, allowing your filter and chemicals to work more efficiently at removing them.
In addition, brushing helps to evenly distribute chemicals throughout the pool and improves water circulation, which reduces dead spots where algae can thrive. While an automatic cleaner can take over after the initial brushing and shocking phase, manually brushing at least once or twice during the cleaning process is essential for a more thorough and faster cleanup.
How can I prevent algae from returning after cleaning the pool?
Preventing algae regrowth starts with maintaining proper water balance and consistent chlorine levels. Algae thrive in unbalanced water, especially when free chlorine is too low or the pH drifts outside the ideal range of 7.4 to 7.6. Regular testing and adjustment of sanitizer levels, along with stabilizer (cyanuric acid) should help protect chlorine from UV degradation.
In addition to chemistry, brushing your pool weekly and ensuring all circulation systems run sufficiently will discourage algae. You can also use an algaecide as a preventive measure, especially if the pool has a history of algae growth. Keeping the pool free of organic debris like leaves and dirt, and ensuring your filter is clean and working properly will also reduce the likelihood of algae returning. With consistent maintenance, your revived pool can stay algae-free all season long.