You might wonder why a pool that receives professional chemical care would ever need to be drained and refilled. You see precise doses of chemicals added and the water looking sparkling clear.
However, water chemistry in a pool is an additive process. Every time chlorine, shock, or water hardeners go into the pool—or every time fresh tap water tops off evaporation—dissolved particles are left behind. Because water evaporates but minerals and heavy chemicals stay behind, the pool gradually becomes saturated over time.
Eventually, no amount of chemical balancing can fix over-saturated water. Here are the three main “saturation culprits” that necessitate a drain and fresh refill every 3–5 years:
1. Cyanuric Acid (CYA) “Lockout”
- What it is: Cyanuric acid (stabilizer) protects chlorine from being destroyed by sunlight.
- The Problem: CYA does not evaporate or break down naturally. Every time stabilized chlorine tabs or shock are added, CYA builds up.
- The Threshold: Once CYA crosses 80–100 PPM (parts per million), it causes Chlorine Lockout. The stabilizer binds so tightly to chlorine that the chlorine loses its power to sanitize. You could have plenty of chlorine in the pool, yet algae will still bloom, and bacteria won’t be killed.
2. Total Dissolved Solids (TDS)
- What it is: TDS measures the sum of everything dissolved in your pool: minerals, salts, dust, swimmer waste, and chemical byproducts.
- The Problem: High TDS leads to dull, lifeless water, salty or chemical tastes, persistent cloudiness, and reduced chemical efficacy.
- The Threshold: When TDS levels exceed 1,500–2,000 PPM above your fill water’s baseline, the water becomes oversaturated. Adding more chemicals to high-TDS water is like adding sugar to a glass of iced tea that already has an inch of undissolved sugar at the bottom—it simply won’t dissolve or work effectively.
3. Calcium Hardness & Scale
- What it is: Calcium is a mineral present in tap water and used to protect pool plaster.
- The Problem: Local tap water is naturally rich in calcium. As heat and sun evaporate pure water, calcium stays behind and concentrates rapidly.
- The Threshold: When Calcium Hardness climbs above 400–500 PPM, calcium precipitates out of solution. It manifests as unsightly white scale on tile lines, rough surface plaster, and calcium buildup inside expensive equipment like pumps and heaters.
The Solution: Controlled Drainage & Water Refill
There are no chemical “neutralizers” that effectively remove high CYA, TDS, or calcium without damaging your pool surface. Draining is the only reliable way to reset your water balance.
A Note on Pool Safety: Draining a pool requires careful timing and execution to protect your pool shell, plaster, and plumbing from hydrostatic pressure issues or surface drying. Never drain your pool yourself without consulting our team first.
Has Your Pool’s Water Reached Its Expiration Date?
Because parameters like CYA, Calcium, and TDS change very gradually over long periods, we don’t test for them on every routine weekly visit—there’s no need to cause unnecessary worry week after week! However, over a 3- to 5-year window, these levels naturally rise to a point where they must eventually be addressed.
Pool Chem Plus can run specialized testing to confirm whether high CYA, Calcium, or TDS levels have reached that threshold. Once evaluated, our team will provide clear, professional recommendations on whether a partial or full drain is necessary to reset your water chemistry and protect your pool investment.
Got questions about your pool’s chemistry or need an assessment? Reach out to the team at Pool Chem Plus anytime!
