You Just Filled Your Pool — What to Do Next (New Fill & New Plaster Start-Up)

“I just filled my pool, now what?” is really two questions wearing one phrase — and the answer depends entirely on what your pool is made of. Any new fill needs a first-week checklist. A new plaster, gunite, or pebble surface needs a careful 30-day start-up on top of that, because the wrong chemistry in those first weeks can permanently damage the finish. Let’s do both, in order.

Which pool do you have?

• Vinyl liner or fiberglass: the surface is inert and already cured — you only need the new-fill checklist below. Skip the plaster section.
• Plaster, gunite, quartz, or pebble: do the new-fill checklist and the new-plaster start-up below. The plaster is still curing and needs protecting.

The new-fill checklist (any pool)

New water is a blank slate — and blank means zero sanitizer and whatever your source water brought with it.

1. Test the fill water first. Fill water — especially well water — can arrive with metals, existing calcium hardness, or even CYA. Run a full test with a good FAS-DPD kit before you dose anything, so you’re correcting reality, not a guess.
2. Add a startup sequestrant. Iron and other metals are hard to detect and brutal to remove once they stain, so a startup dose of sequestrant is cheap insurance (essential if you’re on a well — dose about 1.5× — see metal stains).
3. Start circulation. Get the pump and filter running as soon as the pool is full to mid-skimmer.
4. Add chlorine. New water has none, so it isn’t sanitary until you chlorinate it. Use liquid chlorine to start (see which chlorine to use).
5. Add CYA — with the sock, and undershoot. Dissolve granular CYA in a sock rather than dropping it on the surface or skimmer. Aim low: CYA is a one-way door (you can only lower it by draining and refilling), so start under your target and add more if needed. See the 5 numbers for ranges.
6. Balance the rest — pH, alkalinity, calcium — into range, and don’t swim until it’s balanced.

Need the exact amounts? Enter your pool’s gallons and target and this calculator gives you the dose for chlorine, CYA, alkalinity, and calcium — add the right amount, not a guess.

That’s the whole job for a vinyl or fiberglass pool. If yours is plaster, keep going.

New-plaster start-up: the high-stakes 30 days

Fresh plaster is still curing — cement keeps hydrating for over a month — and it leaches calcium hydroxide into the water. That’s what causes “plaster dust” and drives pH up fast. Here’s the stakes: if the water goes aggressive (low pH, negative LSI) during this window, it pulls calcium out of the surface, leaving permanent microscopic voids that make the finish weaker, rougher, and quicker to stain for its whole life. You can’t undo that. So the entire goal is to keep the water slightly scale-forming (positive LSI) for the first 20–30 days while you brush off the dust.

This is usually your builder’s job. Start-up is typically the plasterer’s warranty responsibility, and skipping their steps can void the warranty — so follow your plaster manufacturer’s written guide and talk to your builder. The below is so you understand the process and can catch a builder who’s about to do something harmful.

Which start-up method? (the honest comparison)

There isn’t one agreed method — but the disagreement is narrower than it looks, and one method is unanimously condemned:

The bicarb and calcium methods are cousins: both just aim to fill with slightly-positive-LSI water so the curing plaster doesn’t have to give up its own calcium. Honest caveat: the formal industry research (the NPIRC studies) came back inconclusive between the methods — so we don’t crown one. But the acid/hot start is condemned across the board — the National Plasterers Council says it causes “extensive, usually unrepairable” damage, and TFP and Orenda agree it’s the worst thing you can do to fresh cement. If a contractor proposes an acid start on your new plaster, that’s your cue to stop and ask questions.

The rules everyone agrees on

Whichever positive-LSI method you use:

• Fill fast, without stopping, using multiple hoses — and don’t let the hose spray directly on fresh plaster. A partial-fill pause leaves a ring at the water line that’s nearly impossible to remove without an acid bath.
• Brush the entire surface twice a day the first week, then once a day the rest of the first month — top of the walls down, shallow to deep, to knock off loose plaster dust.
• Run the filter continuously until the dust is brushed away (the NPC says a minimum of 72 hours, up to seven days).
• Hold LSI slightly positive (roughly 0.0 to +0.3) for the first 20–30 days — see water balance (LSI/CSI). Expect pH to run high while the plaster cures; manage it gently, don’t chase it with aggressive acid.
• No heater until the plaster dust is gone — TFP says about two weeks, the NPC says 28 days; when in doubt, follow the longer window and your manufacturer. Dust clogs and damages the heater.
• No SLAM / no shocking for the first 30 days. Use liquid chlorine to keep it sanitary.
• No salt and no SWG for 30 days (see below).
• No wheeled vacuums or robots until day 28 — brush and non-wheeled cleaning only.

Salt timing: the one live disagreement

Almost everyone says 30 days before you add salt or energize the cell — the NPC, TFP, Orenda, and Pentair all agree. Hayward’s Aqua Rite manual is the outlier at 10–14 days. When the manuals conflict, defer to the longer 30-day window (and your plaster manufacturer): salt is corrosive to green plaster, the cell fights your pH battle, and plaster dust can damage it. Run liquid chlorine for the first month, then add salt and start the SWG.

The expensive mistakes to avoid

1. Adding chemicals on top of each other — never add calcium and sodium bicarbonate together or back-to-back; they react and cloud the water badly. Sequence additions and circulate between them.
2. Running the heater too soon — dust clogs it.
3. Letting pH spike and etch the surface — hold LSI slightly positive.
4. SLAMing in the first 30 days.
5. Wheeled cleaners before day 28.
6. The acid “hot start” — the single most damaging shortcut.

Bottom line: a fresh fill just needs the first-week checklist — test the water, sequester metals, chlorinate, stabilize, balance, and don’t swim until it’s right. A fresh plaster surface needs a month of care on top: keep the water slightly scale-forming, brush twice a day, hold off the heater/salt/SLAM/wheeled cleaners for ~30 days, and never let anyone acid-start it. Get those first weeks right and the finish cures hard and lasts; get them wrong and you’re living with a rough, stain-prone surface you paid a lot for. When in doubt, your plaster manufacturer’s guide and your builder win — it’s their warranty.