"Drain it and refill" is the default answer from vendors who cannot fix chemistry. In most cases it is the wrong answer — expensive, wasteful, and in hard-water areas it hands you a brand-new scaling problem.
Well-maintained pools rarely need a full change
A pool with correct sanitiser, balanced pH and alkalinity, and honest filtration can run for years on the same body of water with routine top-ups. Water does not "expire". What accumulates is dissolved solids.
What TDS actually tells you
Total dissolved solids measures everything dissolved in the water — salts, minerals, chemical by-products, calcium. Compare it to your fill water, not to an absolute number. Once TDS runs roughly 1,500 ppm above your source-water baseline, you will notice:
- Chemicals working sluggishly at correct doses
- Dull, flat-looking water even at good clarity
- Salty taste, and faster corrosion on fittings
The remedy is partial dilution — drain 25 to 40 percent, refill and rebalance. That fixes the problem at a fraction of the cost and risk of a full drain.
When a full drain is genuinely justified
- Structural or tile work that cannot be done underwater
- Cyanuric acid far too high — it cannot be removed chemically, only diluted out
- Severe staining or a bloom after a long abandonment, where the water body itself is unrecoverable
The risks nobody mentions
An empty pool can float or crack from ground-water pressure, plaster left dry in Delhi sun can craze within hours, and refilling from hard borewell supply resets your hardness and scaling problem to worse than where you started. If a full drain is necessary, it should be planned, quick, and immediately rebalanced.
Measure, then decide
Draining should follow a reading, never a hunch. Every SwimCompany visit logs TDS and calcium hardness so a dilution decision is made on trend data. Book a free pool health check to see where your numbers actually sit.