New Pool Start-Up: What to Add, in What Order
Test the fill water first, then add one product at a time with the pump running: chlorine, alkalinity, pH, calcium if needed, and stabilizer. For a new 15,000-gallon vinyl pool filled with water at alkalinity 60 ppm and no chlorine or stabilizer, that is 67 fl oz of 10% liquid chlorine, 6.3 lb of baking soda, and 5.0 lb of stabilizer.
Always follow your product’s label directions. Pool and spa chlorine, bromine, shock and algaecides are EPA-registered pesticides: use products labeled for pool or spa use, and don’t swim or soak until levels are within the limit on your product’s label. If this page and a label disagree, the label wins.
On this page (9 sections)
New water has no sanitizer and no stabilizer. Its pH, alkalinity, calcium, and metals are whatever your tap or well delivers. The calculator turns your fill-water test into an ordered list of doses. The example readings are for illustration only; your fill water will differ, so test before you buy anything.
Test your fill water first
Fill the pool, start the pump, and let it run for a few hours so the sample represents the whole pool. Then test:
- Free chlorine (FC): usually 0 to about 1 ppm from city water, 0 from a well.
- pH and total alkalinity (TA).
- Calcium hardness (CH).
- Stabilizer (cyanuric acid, CYA): 0 in fresh water.
- Metals (iron and copper) if you fill from a well or your water has stained things before.
PHTA's fact sheet on source water lists iron, copper, manganese, calcium, and zinc among the things fill water can bring in, and points to untreated well water as a source of heavy metals. Its advice is to test the source water before you fill. Your city's annual water quality report is a good second check. More on well water: filling a pool with well water.
The start-up order, and why
Sources don't agree on one fixed order. PHTA's alkalinity fact sheet says to correct total alkalinity before adjusting pH or sanitizer. Some product labels start with stabilizer. Our calculator puts chlorine first when FC is below the minimum, so the water is not left unsanitized while you balance it, and then fixes alkalinity before pH. What every source agrees on:
- Add one product at a time, with the pump running and about 30 minutes between products.
- Fix alkalinity before pH, because alkalinity moves pH with it.
- Never mix two products in a bucket, and never add chlorine and acid at the same time.
- Retest before each pH step; earlier steps change the reading.
Example: a new 15,000-gallon vinyl pool
The calculator's example is a vinyl pool filled with water at FC 0, pH 7.6, TA 60 ppm, CH 150 ppm, and CYA 0. The plan:
- Chlorine: 67 fl oz of 10% liquid chlorine, FC 0 → 3.5 ppm.
- Alkalinity: 6.3 lb of baking soda, TA 60 → 90 ppm.
- Stabilizer: 5.0 lb of cyanuric acid, CYA 0 → 40 ppm. It dissolves slowly; retest CYA in about 5 days.
pH 7.6 is already at the top of the target range, so the plan skips that step, and CH 150 ppm is acceptable for vinyl. As the stabilizer dissolves, the chlorine minimum rises with it: about 3 ppm at CYA 40. Keep FC at or above that once CYA reaches its target. The full table is on pool chlorine levels. Always follow the product label.
Vinyl, above-ground, and fiberglass: what changes
The order and the chlorine, pH, and alkalinity targets are the same for every surface. Calcium hardness is where advice differs most:
| Source | Vinyl or fiberglass | Plaster |
|---|---|---|
| ANSI/APSP-11, as quoted by PHTA | 150–1,000 ppm for pools (not split by surface) | |
| An EPA-registered trichlor label (Reg. No. 67262-17) | 175–225 ppm | 200–275 ppm |
| River Pools, a fiberglass pool maker | Fiberglass: less than 120 ppm, and don't add calcium | Not applicable |
Because the sources disagree, follow your pool maker's numbers first. In a vinyl or above-ground pool, there is usually no need to add calcium to normal tap water. For details by surface, see pool chemical levels by pool type and calcium hardness. Brand-specific first-fill notes for Intex pools are on Intex pool chemicals.
Well water and metals: when to use a sequestrant
If your fill water has iron or copper, chlorine can turn it into stains on the liner or plaster. A sequestrant (metal control product) keeps metals dissolved in the water so they don't stain, and PHTA notes that these products can be used when fresh water is added. Use one only if a test shows metals, and dose it by its label. One chemical maker's start-up procedure adds its sequestrant during the fill and starts chlorine the next day, because its product uses up chlorine for several days. If you use a sequestrant, follow its label for when chlorine can go in. If metals are already staining, see pool stains.
New plaster: a different start-up
A newly plastered pool is not covered by this page or our calculator. Fresh plaster needs a day-by-day procedure with brushing and gradual alkalinity and calcium adjustments. The National Plasterers Council publishes a start-up card for this, and your plaster contractor should give you their procedure. Follow theirs; the warranty usually depends on it.
The first two weeks
- Test FC and pH at least once a day; the CDC advises at least twice a day while the pool is in use. The first weeks show how fast your pool uses chlorine.
- Retest CYA after about 5 days and calcium after a week, once everything has dissolved.
- Run the filter long enough each day to pass all the water through it at least once; see the pump run time calculator.
- Brush and vacuum the dust and debris left from setup or filling.
After that, the regular routine is on the pool maintenance schedule. Opening an existing pool each spring is a different job: see the pool opening checklist.
Safety
Never mix chlorine with acid or with another chlorine product. Add each product to the pool separately with the pump running, about 30 minutes apart. Add chemicals to water, never water to chemicals. Wear gloves and eye protection. Keep stabilizer and acid away from chlorine in storage. Don't swim until FC is in range and at or below the swim limit on your chlorine label, and pH is in range. Poison Control: 1-800-222-1222. Always follow the product label. It is a violation of federal law to use a pesticide product in a manner inconsistent with its labeling.
FAQ
How long after filling a pool can you add chemicals?
As soon as the pump has run long enough to mix the water and you have tested it, usually a few hours. If you use a sequestrant for metals, follow its label for when to add chlorine.
Should you shock a new pool after filling it?
Not usually. Clean tap water has nothing to break down, so a normal chlorine dose to your target is enough. Shock only if the water is cloudy or green, at the amount on the product's label.
Do I need stabilizer in a new pool?
In an outdoor chlorine pool, yes. Without stabilizer (CYA), sunlight burns off chlorine quickly. Indoor pools and hot tubs are different: hot tubs should not use it.
When can you swim in a newly filled pool?
When FC is at or above the minimum for your CYA and at or below the swim limit on your chlorine label, pH is in range, and at least 30 minutes have passed since the last product with the pump running.
Sources
- PHTA fact sheet, Source water and its effects on pool and spa maintenance (2020): phta.org (PDF)
- PHTA fact sheet, Total alkalinity (correct TA before pH or sanitizer): phta.org
- PHTA fact sheet, Water conservation during droughts (ANSI/APSP-11 ranges): phta.org
- U.S. EPA, trichlor pool label Reg. No. 67262-17 (calcium ranges by surface): epa.gov (PDF)
- River Pools, Care guide 2025 (fiberglass calcium): PDF
- Orenda, Vinyl liner or fiberglass pool start-up procedure (secondary; one maker's product schedule): orendatech.com
- National Plasterers Council, NPC start-up card: npconline.org
- CDC, Home pool and hot tub water treatment and testing: cdc.gov
- Start-up doses: our engine's full plan; see methodology.