Domakihub How to Balance a Newly Filled Pool — Get It Right First Time
A step-by-step guide to safe, crystal-clear water from the very first fill.
Reviewed by Domakihub pool pros · 2026-06-23 · 5 min read
A freshly filled pool looks inviting, but the water inside is essentially a blank slate — untreated tap water that can be corrosive, cloudy, or a breeding ground for algae within 24 hours. The video above walks through every chemical in plain language; this guide translates those principles into a clear sequence you can follow whether you own a private villa in Crete, a holiday rental on Mykonos, or a hotel pool in Athens. Get the balance right on day one and you will spend far less time and money on remediation throughout the season.
Why Freshly Filled Water Is Not Ready to Swim In
Tap water in Greece typically contains chloramines, varying levels of calcium, and a pH that rarely matches the 7.2–7.6 sweet spot needed for safe swimming. Fill water also lacks any stabiliser (cyanuric acid), which means that even if you add chlorine immediately, the intense Greek sun will burn it off within a few hours. Without a proper baseline chemical balance, swimmers are exposed to eye irritation, skin redness, and — in a commercial setting — potential liability.
A newly filled pool also has no buffering capacity. Small additions of acid or base can swing the pH dramatically, which is why establishing total alkalinity first acts as a chemical shock absorber for everything that follows.
What You Need Before You Start
Gather a reliable test kit (a multi-parameter digital photometer is worth the investment for any property with a pool), and source these five chemicals: a pH increaser (sodium carbonate / soda ash), a pH decreaser (muriatic acid or sodium bisulphate), an alkalinity increaser (sodium bicarbonate), a calcium hardness increaser (calcium chloride), cyanuric acid (stabiliser / conditioner), and your primary sanitiser — chlorine tablets, granules, or a salt-chlorinator if already installed. Allow the pump and filter to run continuously throughout the entire balancing process so chemicals circulate evenly.
5 Steps to Balance a Newly Filled Pool
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Step 1 — Test the Source Water
Before adding a single chemical, test the raw fill water for pH, total alkalinity, calcium hardness, and cyanuric acid. Write the results down. Greek municipal water often arrives at pH 7.8–8.2 and low calcium hardness, but this varies widely between regions. These numbers are your starting point, not a problem yet — you simply need to know how far each parameter is from its target range.
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Step 2 — Adjust Total Alkalinity to 80–120 ppm
Total alkalinity (TA) must be corrected before pH, because TA controls how stable your pH will be. If TA is below 80 ppm, add sodium bicarbonate in doses of roughly 1.4 kg per 40,000 litres per 10 ppm rise. If TA is above 120 ppm, add muriatic acid slowly around the perimeter with the pump running. Wait four hours and re-test before adding more. Getting TA right first saves you from chasing a pH that refuses to hold.
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Step 3 — Balance pH to 7.2–7.6
Once alkalinity is stable, test pH and bring it into the 7.2–7.6 range. Add soda ash (pH up) if it reads low, or muriatic acid (pH down) if it reads high. Broadcast granular products across the water surface and pour liquid acid slowly near a return jet — never near the skimmer. Circulate for two hours and re-test. In Greece's hot climate, aim for the lower end of the range (7.2–7.4) because pH naturally drifts upward through evaporation and aeration.
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Step 4 — Raise Calcium Hardness to 200–400 ppm
Soft water (calcium hardness below 150 ppm) is aggressive: it leaches calcium from plaster, grout, and tile, causing pitting and clouding. Add calcium chloride in stages, pre-dissolving each dose in a bucket of pool water before pouring it in, to avoid the heat spike that undissolved calcium chloride causes. Circulate for six hours between additions. If you have a fibreglass or vinyl-lined pool, the lower end of the range (200–250 ppm) is fine; plaster pools prefer 250–350 ppm.
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Step 5 — Add Stabiliser, Then Shock-Dose with Chlorine
Add cyanuric acid (stabiliser) to reach 30–50 ppm — this protects chlorine from UV degradation, which is critical under the Greek sun. Pour stabiliser slowly through the skimmer with the pump running, then wait 24 hours for it to fully dissolve before testing. Finally, perform an initial shock: add 10 ppm of free chlorine (roughly 150 g of 56% shock granules per 10,000 litres) to sanitise any bacteria introduced during filling. Run the pump overnight, re-test in the morning, and the pool is ready to swim in once free chlorine falls to 1–3 ppm.
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FAQ
- How long after filling a pool can you swim in it?
- You can typically swim 24–48 hours after the initial fill, once all five parameters (alkalinity, pH, calcium hardness, stabiliser, and chlorine) are within target ranges. The limiting factor is usually the stabiliser, which takes 24 hours to fully dissolve, and the shock dose, which must drop below 5 ppm free chlorine before swimmers enter.
- Do I need to balance the pool differently in summer in Greece?
- Yes. High temperatures and intense UV exposure accelerate chlorine consumption and push pH upward through evaporation. During peak summer (July–August), test your pool every 48 hours rather than weekly, keep pH at the lower end of the safe range (7.2–7.4), and ensure stabiliser stays at 40–50 ppm to protect chlorine from the sun. Holiday-rental pools that sit unused mid-week but are heavily used on changeover days benefit from a small shock dose before each guest arrival.
- My newly filled pool is cloudy — is that normal?
- Some mild cloudiness in the first 24–48 hours is normal as chemicals dissolve and the filter establishes its biological layer. However, persistent cloudiness usually signals high pH (above 7.8), insufficient chlorine, or calcium hardness that is too high (above 400 ppm). Test all parameters, correct in the order described above (alkalinity first, then pH, then calcium), and run the filter continuously. If cloudiness persists after 72 hours, a clarifier or flocculent may be needed to help the filter capture fine particles.