What Should You Check After a Major Storm?

TL;DR: After a major storm — defined as heavy rain (1+ inch), high winds, or lightning — check these six things before resuming normal pool use: water chemistry (rain dilutes chlorine and drops pH), water level (heavy rain can overfill), debris (skimmer baskets and the pool floor), equipment operation (power surges can affect controls), pool shell and coping (hail and debris can cause damage), and the surrounding area for any hazards that entered the pool zone. Most post-storm issues are manageable if caught within 24 hours. Scott Payne Custom Pools designs PA and NJ pools with drainage systems that handle typical Northeast storm events without damage.

Storms in the Philadelphia suburbs and western New Jersey are not polite. A fast-moving summer thunderstorm can dump two inches of rain in 45 minutes, drop hailstones, bring 50-mph wind gusts, and leave your backyard looking like a disaster zone. Most pool damage from storms is minor and quickly addressed — but only if you check the right things promptly afterward.

Check 1: Water Chemistry (Priority — Check Within 24 Hours)

Heavy rainfall is the single most significant chemistry disruption your pool experiences during the season. Here's what rain does to pool chemistry:

pH drops: Rain is naturally acidic (pH 5.5–6.0 in most of the PA/NJ region). A significant rain event drives pool pH downward, sometimes dramatically. Low pH is corrosive to your pool's plaster surface and irritating to swimmers. Test and adjust pH first.

Chlorine is diluted: Rain adds clean water to the pool, diluting the existing chlorine concentration. After a heavy rain, your pool may be at or below the minimum chlorine threshold — the condition for algae establishment.

Organic material is introduced: Wind and rain wash pollen, leaves, bird waste, lawn chemicals, and road runoff into the pool. These organic compounds consume chlorine and introduce phosphates and other algae nutrients.

Alkalinity may shift: Rain's acidity also affects total alkalinity, sometimes causing it to drop below the buffering range.

Post-storm chemistry protocol: 1. Test pH — raise if below 7.2 using sodium carbonate (soda ash) or sodium bicarbonate 2. Test and raise chlorine — add shock if chlorine is below 1 ppm 3. Test alkalinity — raise if below 80 ppm using sodium bicarbonate 4. Run the filter for 24 hours after adding chemicals 5. Test again the next day and adjust as needed

Check 2: Water Level

Heavy rain can raise the pool water level above the skimmer opening, which prevents the skimmer from functioning — the water surface is above the skimmer mouth, so surface debris is no longer drawn in. You may also see water overflowing onto the surrounding patio, which affects drainage and hardscape.

If the water level is more than 2 inches above the skimmer mouth: - Use a submersible pump to lower to normal operating level - Alternatively, connect a garden hose to the backwash port (sand or DE filter) and run the filter to waste until level drops

Do not lower the water below the skimmer mouth to avoid pump air-lock — keep it at mid-skimmer height.

Check 3: Debris and Skimmer Baskets

After any storm with wind, expect the pool and skimmer baskets to be loaded with debris. Check in this order:

Skimmer baskets: These are likely full. A skimmer basket packed with leaves and debris restricts water flow, reducing pump efficiency and potentially causing the pump to lose prime.

Pump basket: Storm debris that passed through a full skimmer basket can end up in the pump basket — check and clear.

Pool surface: Remove any large debris floating on the surface with a leaf net before it sinks and stains the pool floor.

Pool floor: Debris that sinks and sits on the plaster surface can cause staining, particularly organic material (leaves, acorns, berries). Vacuum within 24–48 hours after a storm.

Leaf net or storm cover: If you use a leaf net or mesh cover during storms, remove and store it after the storm passes.

Check 4: Equipment Operation

Power surges and lightning can affect pool equipment in several ways:

Automation system: Check the control display for any fault codes or error messages after power restoration. Automation systems sometimes reset to default programming after a power outage — verify your pump schedule and heater setpoint are still correctly programmed.

Salt system: Salt systems are sensitive to power fluctuations. Check the display for error codes and verify the system is producing chlorine normally.

GFCI breakers: GFCI breakers sometimes trip during power events. Check the equipment subpanel and verify all breakers are in the correct position. Reset any tripped GFCIs.

Pump operation: Listen for the pump running normally after power restoration. If the pump lost prime during the outage, you may need to re-prime it before it moves water normally.

Check 5: Pool Shell, Coping, and Tile

Hailstorms are the most likely weather event to cause physical damage to pool surfaces:

Coping: Large hail can chip natural stone coping. Inspect the coping perimeter for chips or cracks.

Tile: Check waterline tile for any cracked or loosened tiles, particularly at the corners where stress concentrates.

Pool surface: Large hail or debris falling into the pool can chip plaster or pebble aggregate, though this is uncommon. Inspect visually for any visible chips or damage.

Expansion joints: Check the flexible sealant joint between the coping and the deck. Storm impact and ground movement can loosen this joint. Gaps in the expansion joint allow water intrusion that accelerates frost-heave damage over time.

Check 6: The Surrounding Area

Before resuming pool use, scan the pool surroundings for storm hazards:

Downed branches or trees near the pool area or equipment pad

Displaced fencing: Check gate hardware and fence alignment — storm winds can lift fence sections or knock gate hardware out of alignment, creating a barrier compliance issue

Equipment debris: Confirm the equipment pad is clear of debris and that no branches or objects impacted equipment covers or housings

Electrical: Do not use the pool if you see any damaged electrical conduit, equipment connections that have been disturbed, or any evidence of water intrusion into electrical components. Call an electrician before re-entering the pool.

Frequently Asked Questions

Is it safe to swim in a pool immediately after a thunderstorm?

No. The standard guidance is to wait 30 minutes after the last thunder or lightning strike before re-entering the pool. Lightning can strike the water before visible clouds are overhead, and the risk persists for a period after the storm passes. Beyond the immediate safety window, the chemistry disturbance from heavy rain warrants testing and adjustment before the pool is used.

My pool overflowed during a major rain event. Is this a problem?

An occasional overflow from a truly exceptional rain event (3+ inches) is usually not a significant problem if it happens infrequently. Chronic overflow events suggest that your pool's drainage plan isn't managing normal rainfall adequately — a drainage engineering concern worth addressing. Consistent overflow can accelerate erosion around the pool perimeter, stress the hardscape, and introduce runoff chemistry into the pool repeatedly.

Can lightning strike a pool through the water?

Lightning can strike the water surface directly or indirectly through electrical systems. A lightning strike at or near a pool that has inadequate bonding creates a voltage gradient in the water that can injure or kill swimmers. This is why pool bonding (the continuous copper wire connecting all metal components throughout the pool system) is a federal safety requirement. If your pool's bonding system is intact and properly installed, a nearby lightning strike doesn't necessarily create water electrocution risk — but the safest course is to exit the pool at any sign of thunderstorm activity.

A tree fell and debris went into my pool. What do I do?

Remove debris carefully — use a leaf net for surface debris, vacuum for settled material. Test chemistry and shock the pool. Inspect the pool surface where heavy debris may have impacted. If a large branch or tree fell directly into the pool and you have concerns about shell damage, have a pool professional assess before regular use. Organic material from trees (particularly pine needles and certain leaf types) can stain plaster quickly — prioritize removal within 24 hours.

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