Partial Drain
A partial drain is the process of removing a portion of pool water and replacing it with fresh water to dilute accumulated dissolved compounds.
Definition
A partial drain is the process of removing a portion of pool water and replacing it with fresh water to dilute accumulated dissolved compounds.
Typical Values: 25% partial drain removes 25% of all dissolved compounds; timing depends on season and reason
In Plain Language
Partial drains are used to reduce CYA, calcium hardness, TDS, and salt that cannot be lowered by chemical treatment. A 25% partial drain reduces all dissolved compounds by 25%. A 50% drain reduces them by 50%. For example, if CYA is at 100 ppm and the target is 50 ppm, a 50% drain brings it back to the target. The fresh refill water typically adds back a small amount of the compounds depending on the tap water quality.
Why It Matters
Partial drains are the only method for reducing CYA, TDS, and other accumulated compounds in pool water.
Typical Values
25% partial drain removes 25% of all dissolved compounds; timing depends on season and reason
Last reviewed: 2026-06-01