For many pool owners in Zimbabwe, the combination of high chemical costs and heavy seasonal rains can make the idea of draining the pool to “start fresh” seem logical. However, this practice is one of the most damaging and costly mistakes you can make. This article explains the severe risks of prolonged pool draining, its interaction with our rainy season, the specific threat to popular Marbelite finishes, and why this method fails as a chemical-saving strategy.
Why Draining Your Pool is a Structural Gamble
A full or prolonged drain of an in-ground pool creates immediate physical dangers. The primary threat is hydrostatic pressure—the pressure exerted by groundwater in the soil surrounding your pool.
When your pool is full, the internal water weight balances this external pressure. Removing that weight, especially during or after our rains when the water table is high, can cause catastrophic failure:
- “Pop-out” Effect: The groundwater pressure can literally lift or pop the entire pool structure out of the ground. A popped pool cannot be simply pushed back down; it requires complete, expensive reconstruction.
- Wall Collapse (Vinyl Liner Pools): Vinyl liner pools rely on the water to hold their shape. Without it, walls can buckle or collapse.
- Cracking: Concrete and plaster shells, including Marbelite, can crack as they dry and contract, only to expand and delaminate when refilled.
Beyond the structure, draining damages equipment. Pumps and filters can burn out if they run dry, and heaters can be ruined if activated without water flow.
The Rainy Season Multiplies the Risk
In Zimbabwe, the rainy season doesn’t just add water; it dramatically increases the peril of an empty or lowered pool.
The Hydrostatic Pressure Surge
Heavy rains saturate the ground, causing the water table to rise significantly. An empty pool acts like a boat in a rising tide—the buoyant force from below becomes immense. Professionals strongly advise against removing water during heavy rain for this exact reason. The risk of the pool floating or popping is at its peak.
Chemical and Contamination Chaos
Even if you only partially drain, rainwater causes major chemical issues:
- Acidic Dilution: Rainwater is naturally acidic. A heavy downpour dilutes your carefully balanced pool chemistry, crashing chlorine levels and lowering pH and alkalinity. This acidic, under-sanitized water becomes corrosive and a breeding ground for algae.
- Contamination Influx: Rain washes dirt, organic debris, algae spores, and pollutants into the pool. This overloads your filtration system and consumes sanitizers, making the water cloudy and unsafe.
The Special Vulnerability of Marbelite Finishes
Marbelite (a high-quality plaster finish common in Zimbabwe) is particularly vulnerable when a pool is drained. Its warranty and longevity are directly tied to proper water maintenance.
Voided Warranty
The Marbelite warranty is explicitly void if the pool is drained during the warranty period. Manufacturers state that the finish is designed to cure and exist underwater. Draining removes this essential element, absolving them of responsibility for resulting damage.
Physical Damage to the Finish
Marbelite undergoes a long curing process underwater. Draining exposes it to:
- Drying and Cracking: The plaster can dry out, shrink, and develop webs of fine cracks or major fractures.
- Staining and Etching: Without balanced water to protect it, the surface becomes susceptible to permanent staining and etching from environmental elements.
- Improper Curing (New Finishes): For new Marbelite, filling must begin within 6-72 hours of application, and the pool must remain filled for the first 6 months for proper curing. Draining during this period ruins the finish.
The Root Cause: Misunderstanding Water Chemistry
The desire to drain often stems from frustration with persistent algae, cloudiness, or high chemical demand. The root cause of these issues is almost always a chemical imbalance, not the water itself.
Common culprits include:
- Low Chlorine: Ineffective sanitation allows algae to bloom.
- Incorrect pH/Alkalinity: This renders chlorine ineffective and can make water corrosive or scale-forming.
- High Cyanuric Acid (Stabilizer): Levels above 80-100 ppm can “lock” chlorine, making it useless.
- High Phosphates: These are food for algae.
- Poor Filtration/Circulation: A clogged filter or inadequate pump runtime cannot clean the water.
Draining is a radical “solution” that addresses none of these underlying chemistry problems and instead introduces major structural risks.
Why Draining is a False Economy for Saving Chemicals
Choosing to drain your pool to reset chemicals is a costly illusion. Here’s why:
1. The “Fresh Start” is Short-Lived: Tap or borehole water in Zimbabwe is often hard (high in calcium) and unbalanced. Filling a pool with it requires significant chemicals from day one to adjust pH, alkalinity, calcium hardness, and to establish sanitation—just as the old water did.
2. You Pay for Water Twice: You incur the cost of the thousands of litres of new water, plus the cost of chemicals to balance it.
3. You Risk a Catastrophic Bill: The potential cost of repairing a popped pool, a cracked Marbelite finish, or collapsed walls dwarfs a decade’s worth of chemical expenses.
4. Its Unnecessary: Any water quality issue—green algae, cloudiness, high dissolved solids—can be corrected without draining through systematic testing and chemical treatment. A partial drain-and-refill (never below skimmer level) can help dilute high stabilizer or calcium levels at a fraction of the risk.
The Safer, Smarter Alternatives
- Master Testing: Regularly test and balance pH (7.2-7.6), Alkalinity (80-120 ppm), and Chlorine (1-3 ppm). Address problems immediately.
- Pre-Rain Preparation: Before storms, raise chlorine levels slightly and ensure good drainage around the pool.
- Post-Rain Action: After rain, test water immediately, rebalance chemicals, remove debris, and shock the pool if needed.
- Partial Water Exchange: If levels are too high, lower the water level slightly (via waste setting) and top up with fresh water to dilute impurities gradually.
- Professional Help: Consult a local pool professional for persistent issues. They can offer solutions like water recycling services that filter out impurities without draining.
Conclusion
For Zimbabwean pool owners, draining your pool—especially for prolonged periods or during the rainy season—is a high-risk endeavor that threatens your pool’s structure, destroys your Marbelite finish, and fails to achieve its goal of saving money. The true path to a clear, healthy, and cost-effective pool is consistent, knowledgeable chemical maintenance and filtration. Protect your investment by keeping your pool full, balanced, and circulating.
