Filling a pool for the first time, or refilling one after fresh plaster, marble, quartz, pebble, or glassbead resurfacing, calls for a different water-chemistry sequence than reopening an already-cured pool each season. Fresh plaster is vulnerable during its first weeks: chemicals added in the wrong order or too early can etch or discolor the surface. This guide follows the 28-day fresh-fill start-up procedure published by the National Plasterers Council (NPC) via the Pool & Hot Tub Alliance (PHTA), which is distinct from the seasonal reopening checklist used for a pool that has already cured.
Key Facts
- Do not add chlorine for the first 48 hours after filling; sanitizer is introduced gradually starting Day 3, once alkalinity and pH are balanced.
- Total alkalinity is balanced first (80-100 ppm), then pH (7.2-7.6), then calcium hardness in stages — never add calcium hardness increaser and alkalinity increaser at the same time.
- Cyanuric acid is not introduced until Day 4 at the earliest, added slowly through the skimmer over a minimum of 3 days.
- Brush the entire pool surface at least twice daily until all plaster dust is removed — undissolved dust can settle and etch the new finish.
Why This Is Different From Reopening a Pool
Reopening an existing pool for the season means restoring balance to water that has already cured against the pool's surface for years. A fresh fill or a newly plastered pool is different: the plaster itself is still curing and chemically reactive for its first 28 days, and the fill water has not yet been tested or balanced at all. Adding chlorine or shock immediately, or adjusting chemistry out of the recommended order, is a common cause of etched, mottled, or discolored new plaster. The sequence below (alkalinity, then pH, then calcium hardness, then chlorine, then cyanuric acid) exists specifically to protect a curing surface, not just to reach target ranges quickly.
Days 1-3: Alkalinity, pH, and the First Chlorine
Before filling, test the fill water itself for pH, total alkalinity, calcium hardness, and metals. On Day 1, adjust total alkalinity to 80-100 ppm, then pH to 7.2-7.6. Begin raising calcium hardness in small increments (roughly 10-pound doses of calcium chloride, several hours apart, never at the same time as an alkalinity adjustment) toward 80-100 ppm on Day 1 and 100-150 ppm on Day 2. Run the pump and filter continuously for at least the first 72 hours to clear plaster dust. Do not add chlorine for the first 48 hours. On Day 3, once alkalinity, pH, and calcium hardness are on track, add chlorine gradually to bring free chlorine to 1.5-3 ppm.
Days 4-28: Calcium Hardness, Cyanuric Acid, and Ongoing Care
By Day 4, calcium hardness should be at least 200 ppm. This is also the earliest point to begin adding cyanuric acid, brought to 30-50 ppm slowly through the skimmer (with the skimmer and pump baskets removed) over a minimum of 3 days — concentrated CYA added too quickly can discolor pigmented plaster finishes. Continue brushing the entire surface at least twice daily and testing frequently through Day 7, tapering to about once a week once plaster dust is fully removed and a normal cleaning routine is in place. Keep records of every test and chemical addition. For saltwater pools, do not add salt within the first 30 days; for any pool, do not run the heater until the plaster manufacturer's recommended waiting period has passed (commonly 2-4 weeks), and do not shock the pool during this 28-day window.
Examples
A newly plastered 18,000-gallon pool is filled with municipal water. Day 1 testing shows total alkalinity at 140 ppm (high) and pH at 7.9; muriatic acid is pre-diluted in a bucket and added to bring alkalinity to about 95 ppm, then pH to 7.4. Calcium hardness starts at 40 ppm, so calcium chloride is added in 10-pound doses over Day 1 and Day 2, reaching 120 ppm. The pump runs continuously and the surface is brushed twice daily. On Day 3, with alkalinity and pH holding, chlorine is added gradually to reach 2 ppm free chlorine. By Day 4, calcium hardness has reached 210 ppm, and CYA is introduced through the skimmer over the next 3 days to reach about 40 ppm. No shock, salt, or heater use occurs during this period.
Common Mistakes to Avoid
- Adding chlorine or shock immediately after filling instead of waiting the required 48 hours — this is one of the most common causes of new-plaster etching.
- Adding calcium hardness increaser and alkalinity increaser at the same time instead of spacing them out.
- Skipping or reducing brushing frequency once the water looks clear, even though plaster dust is still settling.
- Treating this sequence as interchangeable with the seasonal opening-pool checklist — a newly plastered surface is still curing and needs the staged order above, not a quick balance-and-swim routine.
- Pool & Hot Tub Alliance (PHTA), Recreational Water Quality Committee — Fresh Fill Water Start-Up for Plastered Pools, March 2021 (procedure developed by the National Plasterers Council)