After a heavy rainstorm, your swimming pool can suffer in ways that aren’t always immediately obvious. Standing water, debris, and chemical imbalances can quickly turn a peaceful backyard oasis into a potential health hazard. If you’re wondering what to do to your pool after a heavy rain, this guide will walk you through each necessary step—from inspection to maintenance, ensuring your pool remains safe and sparkling clean.
Whether you own an in-ground chlorinated pool or an above-ground saltwater system, understanding proper post-rain care can prolong your pool’s lifespan and minimize costly clean-up or repairs. Let’s dive into everything you need to know to restore your pool after a heavy downpour.
1. Initial Inspection: Safety First
Before jumping straight into cleaning, your first priority should be safety. A post-rain environment may hide serious hazards.
Check for Structural Damage
Inspect your pool’s edges, tiles, coping stones, and decking for signs of damage caused by water pressure or displaced objects. In-ground pools may be more vulnerable to shifting or cracking, especially following a severe storm or flooding.
- Look for signs of leaks such as sunken or muddy spots around the pool structure
- Inspect the filter system and pool equipment for water intrusion or damage
- Ensure all pool lights are covered and dry before powering them on
Survey the Electrical System
Pools rely on a network of electrical equipment. If any part of your pool’s electrical component has been submerged, disconnect power immediately and seek professional help. You should not attempt to operate or manually inspect electrical systems unless you’re 100% certain they are dry and intact.
Key Points:
- Never plug in the pump if there’s standing water near equipment.
- If your breaker may have tripped, label and log the issue before resetting.
- A faulty electrical system can lead to shocks or equipment failure.
2. Remove Excess Surface Water and Debris
One of the first challenges after heavy rain is excessive water on the pool surface. A full pool could overflow, altering chemical balance and potentially damaging surrounding structures.
Skim the Surface First
Use your manual skimmer net to remove leaves, dirt, sticks, and any other floating debris. The faster you do this, the easier it will be to avoid staining or filter clogging later.
Use the Pool Pump or Manual Pump
If the water level has risen significantly:
- Use your pool pump on the “drain” setting if available
- If your pump cannot lower water enough, a submersible sump pump can help lower the level quickly
Ideally, you want to bring the water level to just slightly below the skimmer (about halfway up the tile line).
Tip:
Avoid lowering the water level too much if you have an in-ground pool unless the ground water could cause hydrostatic pressure that threatens to lift the pool structure.
3. Test and Adjust Chemical Levels
Heavy rain often introduces rainwater runoff, which can be slightly acidic or laden with debris and contaminants. In turn, this dilutes the pool water, changing key chemical balances.
Common Imbalances to Expect:
| Chemical | Effect After Rain |
|---|---|
| Chlorine | Likely reduction due to water volume increase; possible algae bloom |
| pH | May drop due to acidic rain or increase from debris |
| Alkalinity | Usually lowered by heavy volumes of rain |
| Calcium Hardness | Possibly unchanged unless the refilling involved well or softened water |
To begin the chemical restoration process, use a high-quality pool testing kit. Focus on the following:
- pH level (ideal range: 7.4–7.6)
- Free chlorine levels (recommended 1–3 ppm)
- Total alkalinity (TA) – maintain between 80–120 ppm
- Calcium hardness (200–400 ppm for vinyl, 200–275 for plaster or marcite surfaces)
Important:
Remember, even if your pool has a saltwater system, rainwater dilutes the salt content. You’ll need to test for salinity and adjust accordingly.
Once you’ve taken readings, adjust the levels with appropriate chemicals. Make adjustments gradually to avoid overdosing, which may create other water quality issues.
4. Run the Filtration System
Once the water is at the proper level (below the skimmer) and basic chemicals are balanced, it’s time to get the water circulating.
Run the Pump for Long Cycles
After a pool refill or storm exposure, run the pump for at least 8 to 12 hours per day for several days to help stabilize chemical distribution and remove particulates.
Backwash or Clean the Filter
Given that the filter likely trapped a lot of debris from the storm, you should clean or backwash it depending on the system:
- Sand filter: Switch to the “backwash” position and run until the water runs clear (this may take 3–5 minutes).
- Cartridge filter: Remove the cartridge and rinse thoroughly with a hose.
- Diatomaceous Earth (DE) filter: Backwash and then re-charge the filter with DE powder.
Note:
Once the filter has been cleaned, ensure it’s primed correctly before restarting to avoid air locks or low circulation.
5. Scrub and Vacuum
Despite the rain “washing” much of the exposed area, your pool is still at risk of algae spores and localized staining.
Manually Brush All Surfaces
Start by manually scrubbing all walls and corners. Algae and microorganisms tend to attach to the pool walls, especially if chlorine levels dipped during the rain.
Use a brush appropriate for your pool surface:
- Vinyl liner pools – Use nylon brushes to avoid tears or scratches.
- Concrete (plaster) pools – Stiff brushes are okay and often preferred.
- Fiberglass pools – Use softer brushes to preserve finish.
Check for Algae or Discoloration
Pay special attention during brushing to any greenish or darker patches. These could be early signs of algae bloom.
If algae is visible:
- Scrub it off thoroughly.
- Shock the pool with a high dose of chlorine.
- Use an algaecide to prevent regrowth.
Use your vacuum system next. Pool vacuums—whether manual or automatic—help remove the dirt and particulates brought in by the storm runoff and rain.
6. Shock the Pool to Reclaim Sanitation
Even if chemical levels were slightly balanced earlier, shocking the pool after heavy rain is essential for ensuring full sanitation and oxidizing any contaminants.
Types of Pool Shock and Their Uses
| Shock Type | Best For | Notes |
|—————–|———————-|——————————-|
| Calcium Hypochlorite | High sanitization needs | Adds calcium to water |
| Dichlor | Stabilized chlorine | UV-resistant, but can raise CYA levels |
| Lithium Hypochlorite | Balanced effect | Dissolves quickly, safer when kids nearby |
| Non-chlorine shock | Oxidization without adding chlorine | Good for maintenance in between shocks |
When to Shock:
- After each heavy rainstorm
- Whenever pool water becomes cloudy or has visible algae
- After heavy bather load or contaminant introduction (runoff from fertilizer use, pet access, etc.)
Remember: To shock your pool, use about 1 pound of shock per 10,000 gallons of water. Always follow label instructions carefully.
7. Maintain the Pool Surrounding Area
While the pool water can absorb rain’s impact, the backyard around the pool also takes a hit. Debris, standing water, and wet chemicals can pose ongoing hazards.
Clean Up the Decking and Gates
Use a garden hose and mild detergent to wash off your pool deck. This prevents slip hazards and removes chemicals that may have splashed from the pool.
Check for Standing Water and Drainage Issues
If water is pooling next to your pool equipment or deck, solve the issue proactively:
- Clean gutters and nearby drains
- Use sandbags or redirect garden slopes for better drainage
- Consider installing a catch basin or French drain for persistent standing water
Preventing Future Damage:
Over time, heavy rains can create washouts, erosion issues, or even mildew around pool decks and equipment compartments. Investing in proper grading and rainwater management can protect all outdoor pool assets.
8. Inspect and Maintain Pool Equipment
Once everything dries out (or as much as possible after a storm), inspect and maintain all pool equipment.
Inspect Pumps, Filters, and Timers
- Ensure all systems are dry, especially if they were flooded
- Use fans to dry wet equipment cabinets
- Check for rust, leaks, or unusual odors from electrical units
Check Salt Chlorinators and Digital Controllers
If your pool uses a salt system, inspect:
- Salt cell for scale buildup (rinse in acid if indicated)
- Digital control units are functional with no display errors
- Salt level is sufficient (test with appropriate meter)
Tip:
After heavy rain, use a voltage meter to ensure proper operation of automation systems. Avoid turning on equipment if you suspect moisture remains in sensitive areas.
9. Monitor for Algae Over the Next Few Days
Even with aggressive chemical balancing and brushing, algae can make a comeback if conditions are right (low chlorine, high temperature).
Look Beyond the Obvious
Check corners and below the waterline:
- Algae in early stages may appear as slick patches rather than green clumps
- Black algae can embed in cracks and be difficult to remove completely
Address Algae Proactively
If you suspect algae:
- Boost chlorine level to 3–4 ppm
- Use a clarifier or algaecide to help break organic layers
- Vacuum thoroughly, possibly daily until the problem resolves
Reminder: Once you’ve treated the pool, continue testing your chemistry at least once a day for three to five days to ensure algae doesn’t return.
10. Preventative Strategy: Reduce Post-Rain Work
After every storm comes an opportunity to improve your pool maintenance routine and make future clean-ups easier.
Use a Good Pool Cover
Invest in a high-quality solid safety cover or automatic pool cover system if feasible. These can significantly reduce debris and rainwater intrusion.
Install Drainage Solutions
Proper landscaping or the addition of storm drains around your pool can keep rainwater from directly flowing into the pool during storms.
Keep Supplies Nearby
Store pool skimmers, brushes, chemicals, and testing kits in a convenient, waterproof container for easy access after a sudden storm.
Smart Strategy:
Integrate a smart pool monitoring system if possible. These devices notify you via app if key chemical levels dip, helping you react before real problems arise.
11. When to Call a Professional
Despite your best efforts, some situations are better handled by pool professionals:
- If your pool is cracked or shows signs of lifting
- Electrical systems show signs of water damage or failure
- Chlorine levels continue to drop without visible cause, pointing to possible organic contamination
- Persistent algae or water clarity issues
Swimming pool companies offer post-storm inspection and maintenance services that can give you peace of mind and protect your investment long-term.
Conclusion
Knowing what to do to your pool after a heavy rain is crucial not only for aesthetics but also for safety and long-term equipment care. The aftermath of heavy rainfall requires prompt action—ranging from chemical adjustments to physical cleaning and inspection.
Here’s a fast recap of what not to skip:
- Ensure safety and power systems are in check
- Lower water level and skim debris
- Test and rebalance chemicals, especially chlorine and pH
- Brush walls, shock the water, and vacuum frequently
- Monitor for algae and adjust maintenance as needed
Taking the time to restore your pool after heavy rain isn’t just a response—it’s a way to ensure better care and preparedness for the seasons to come. With a proactive, consistent maintenance approach, even the heaviest storms won’t keep you out of the water for long.
If you found this article helpful, consider bookmarking it for your next post-rain workout—or better yet, share it with fellow pool owners in your community!
Why is it important to check the water level after heavy rain?
After heavy rain, your pool’s water level can rise significantly, which may lead to several issues. Excess water can dilute the chemical balance, reducing the effectiveness of chlorine and other sanitizers. It can also put pressure on the pool structure, especially in in-ground pools, potentially causing damage to the skimmer or even leading to flooding around the pool area. Knowing how high the water has risen helps you determine the next steps for restoration and maintenance.
To address this, first locate the skimmer and check the current water level. Ideally, the water should be at about the midpoint of the skimmer opening. If it’s too high, consider using a submersible pump to remove some water, but be careful not to lower it below the skimmer level. Also, make sure to inspect the surrounding area for signs of erosion or structural damage that might have occurred during the storm. This initial step is critical to maintaining the long-term health of your pool.
How should I test and adjust the chemical balance after a rainstorm?
Rainwater can carry contaminants like pollen, dirt, and airborne pollutants into your pool, altering the chemical composition. To address this, use a reliable test kit or bring a water sample to a local pool store for a professional analysis. Pay particular attention to pH levels, total alkalinity, and chlorine concentrations, as these are most commonly affected by dilution and runoff.
Once you’ve reviewed the results, adjust the chemical levels accordingly. For instance, if the pH is too low, you may need to add a pH increaser. Similarly, if chlorine levels have dropped too low, shock the pool after balancing other levels appropriately. Maintaining the right chemical balance prevents algae growth and ensures the water remains safe and clear for swimming.
What steps should I take to clean debris out of my pool?
After a heavy rainstorm, debris such as leaves, twigs, dirt, and even small animals may end up in your pool. To begin the cleaning process, use a leaf net or skimmer to remove large items floating on the surface. Follow up with a pool brush to scrub walls and steps, making sure to dislodge any settled particles or algae growth that might have developed due to poor circulation during the storm.
For fine debris settled on the pool floor, a vacuum or automated pool cleaner is your best bet. It’s also advisable to empty the skimmer and pump baskets, which may have collected significant amounts of debris during and after the storm. Keeping the pool free of contaminants prevents filtration issues and reduces the chemical demand required to maintain water clarity and cleanliness.
Why should I inspect the filtration system after rain?
Rain can introduce a significant amount of dirt, oils, and other pollutants into your pool, which places extra strain on your filtration system. If the filter is clogged or working inefficiently, it won’t clean the water properly, leading to cloudy water and potential long-term damage. Inspecting your filter system post-rain helps you identify early warning signs of damage or inefficiency and ensures it’s functioning optimally to maintain water quality.
Check the filter pressure gauge to see if it’s operating within the normal range. If the pressure is unusually high, backwash a sand or cartridge filter, or clean the grids in a diatomaceous earth (DE) filter. Also, inspect the pump for electrical issues, water leaks, or clogs. Ensuring your filtration system is working correctly allows it to better handle the higher-than-normal demand placed on it after storm conditions.
How can heavy rain affect the pool’s circulation and what can be done?
Proper circulation is crucial to evenly distributing chemicals and preventing stagnant water, which can lead to algae growth. Heavy rain may disrupt water flow patterns by increasing the surface water level and reducing the efficiency of the skimmer and return jets. Additionally, debris introduced by the storm might block water flow paths, further inhibiting circulation and filtration.
To counteract this, run your pump for extended periods—ideally 24 hours a day—to ensure proper circulation. Check and clean return jets to ensure they are not blocked by debris or sediment. Adjust their angle downward to enhance water movement along the pool bottom. Also, use a pool brush to scrub the floor and steps, which helps circulate settled areas. Good circulation is key to recovering from a storm and restoring the clarity and balance of your pool water.
What should I know about algae and bacteria after rain?
Rain introduces nutrients and organic material into the pool, creating a perfect environment for algae and bacteria to thrive. Poor circulation and diluted chemicals further contribute to this risk, especially if the pool isn’t treated quickly. Algae blooms can appear within 24 to 48 hours, turning the pool green or leaving black spots depending on the type, which can be difficult and time-consuming to treat if not addressed immediately.
To prevent algae and bacterial growth, it’s important to shock the pool with a chlorine-based product after rebalancing your chemical levels. Using an algaecide after shocking can help ensure any remaining spores are eliminated and provide some future protection. Additionally, brushing the walls and floor dislodges any early-stage algae growth clinging to surfaces, making it easier for sanitizers to eliminate them. Taking these steps promptly helps mitigate potential health risks and keeps your pool inviting for users.
Is it safe to swim immediately after heavy rain, and why or why not?
It’s usually not advisable to swim immediately after heavy rain due to a combination of safety and sanitation concerns. Stormwater runoff can introduce harmful bacteria, pesticides, and other pollutants from the roof and surrounding ground into your pool. These contaminants may pose health risks, especially for individuals with weaker immune systems or skin sensitivities.
Additionally, electrical hazards such as waterlogged equipment or nearby downed power lines can create serious safety threats. It’s always better to wait at least a few hours after the rain stops, giving time for debris to settle and chemicals to mix properly after treatment. During this time, check the pool’s chemical balance and visually inspect for any contamination or structural issues before allowing anyone to swim. Ensuring safety before re-entering the pool helps protect swimmers’ health and prevents avoidable accidents.