Stop draining your pool before a typhoon

Why Rain Changes Your Pool Water So Fast

A pool that looked perfect at lunch can look tired by dinner after a Metro Manila downpour. Several things happen at once.

• Dilution. Every centimetre of rain on the pool adds fresh water with no sanitiser in it. Chlorine levels drop straight away.
• Acidity. Rainwater is naturally slightly acidic and carries almost no minerals. It pulls pH and total alkalinity down, so the water stops buffering properly.
• Runoff. Water sheets off the deck, garden beds, and roofs into the pool, carrying soil, leaves, pollen, and fertiliser. Those nutrients feed algae.
• Less sunlight. Overcast days slow algae less than people expect. Warm, nutrient-rich, under-chlorinated water grows algae whatever the sky looks like.

The result is a pool that drifts green or cloudy within a day or two after a storm, even though nobody did anything wrong. Our guide to pool water treatment in a tropical climate explains the four numbers that keep the water stable.

The Rainy-Season Routine

1. Test the water after every heavy rain, not on a fixed weekly day.
2. Correct total alkalinity first, then pH, then chlorine. Chlorine works poorly in unbalanced water.
3. Skim and empty the skimmer baskets daily while leaves are falling.
4. Keep the filter clean. A filter loaded with fine silt circulates water without cleaning it.
5. Run filtration longer than in the dry months. The extra organic load needs more turnover.

Typhoon Preparation for Your Pool

When PAGASA raises a signal for your area, run through this list in order.

Do Not Drain the Pool

This is the most damaging mistake owners make. During heavy rain the ground around the pool saturates and the water table rises. Groundwater then pushes up on the underside of the shell. A full pool resists that force with the weight of its water. An empty pool can lift, crack at the floor, or shift. Leave it full. If the deck drains poorly and the pool usually overflows into the house, an experienced technician can lower the level slightly, but never empty it.

Cut the Power

Switch off the pump, any heater or heat pump, the lighting, and the chlorinator at the breaker before the storm arrives. A pump running during a power fluctuation, or sitting in floodwater while live, gets damaged and becomes a hazard. If your equipment pad floods every year, plan to raise it.

Secure the Surroundings

• Move loose furniture, pots, and umbrellas indoors so wind cannot throw them into the pool or through a window
• Close and tie down a solid safety cover if you have one. Remove a light leaf net, which tears and fills the pool with debris
• Clear the deck drains and gutters that discharge near the pool
• Add a normal dose of chlorine the evening before, so the water starts the storm sanitised

Cleaning Up a Pool After a Typhoon or Flood

Order matters. Restarting the pump too early is the second most common mistake after draining.

1. Check safety first. Look for fallen power lines, damaged fencing, and broken glass on the deck before anyone gets close.
2. Remove debris by hand. Net out leaves, branches, and anything else floating or on the floor. Running the pump with heavy debris in the pool clogs the skimmer line and loads the filter in minutes.
3. Inspect the equipment. If water reached the pump motor, the electrical panel, or the chlorinator, keep the power off and get them checked and dried before switching on.
4. Clean the filter. Backwash a sand filter or wash the cartridges before the first full cycle.
5. Test and balance. Correct alkalinity and pH first, then shock with chlorine to break down the organic load.
6. Brush and vacuum. Brush walls and floor to lift settled silt, then vacuum to waste if the silt is heavy, so it leaves the system instead of returning through the filter.
7. Run filtration continuously until the water clears and the chlorine holds steady for a full day.

When Floodwater Entered the Pool

Floodwater from streets and creeks can carry sewage and chemicals. If brown floodwater flowed into the pool, nobody should swim until the water is treated, tested, and clear. Heavy contamination can mean partially draining and refilling. With the ground still saturated, that decision needs someone who checks groundwater first, for the same reason you did not drain before the storm.

What the Rainy Season Reveals About Your Pool

Every rainy season stress-tests the pool's construction. After the last storm of the year, walk the pool and look for these signs.

• Water loss that continues in dry weeks. Rain hides leaks by topping the pool up. If the level drops once the rain stops, run the bucket test in our leak detection guide.
• Loose or hollow-sounding tiles at the waterline. Repeated wetting and heating exposes failing adhesive. Our tile and resurfacing guide explains the tap test.
• Grout washing out or coping lifting where deck water drains toward the pool.
• Soft or sunken paving beside the pool, which can point to washed-out backfill or a plumbing leak.
• An equipment pad that flooded. Raising it, adding a drain, or roofing it costs far less than replacing a pump every other year.

Pools that drain deck water away from the shell, sit on properly compacted backfill, and carry sound waterproofing come through the rainy season with nothing more than a chemistry correction. Pools that do not reveal it, a little more each year. If yours keeps struggling, our pool renovation team starts with a diagnosis, not a quote.

Part of our guide to pool renovation in the Philippines. Related: saltwater vs chlorine pools. Want the water handled for you all year? See our pool maintenance service.