Pool, Spa & Water Treatment Chemistry calculator
Pool Make-up Water Rate Calculator
Turn backwash, splash-out, evaporation, leak, or drain/refill volumes into a daily make-up water rate.
What this calculator does
- Estimate make-up water need from backwash, splash-out, evaporation, leaks, and operating days.
- Use it for water purchasing, salt dilution planning, or facility water-use reporting.
- Turns total make-up water volume, operating period, meter or estimate factor into a practical gal / day result for make-up water rate.
Formula used
- Make-up water rate = total make-up volume / operating days x factor
Inputs explained
- Total make-up water volume: Include backwash, splash-out, partial drains, leaks, and evaporation replacement.
- Operating period: Use the number of days in the reporting or planning period.
- Meter or estimate factor: Use 1 for direct measurements or adjust for known meter bias.
How to use the result
- Use it when planning pool, spa, aquatics, service-route, or water-treatment chemistry adjustments.
- Use the result for planning math only. Follow product labels, health codes, local regulations, test-kit instructions, chemical safety rules, and qualified pool operator guidance before dosing water.
Common questions
- What is the make-up water rate calculator for? Estimate make-up water need from backwash, splash-out, evaporation, leaks, and operating days.
- What numbers do I need for make-up water rate? You need total make-up water volume, operating period, meter or estimate factor. Use measured test results and the same pool, spa, tank, or treatment volume for every input.
- How should I use the result? Use the result to check dose size, run time, flow, inventory, or operating cost before changing a treatment plan or purchase order.
- What should I verify before acting? Verify water volume, units, chemical strength, product label directions, bather load, local code, and current test results. Retest after treatment and never mix incompatible chemicals.
Last reviewed 2026-05-12.