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Coming back to a pool after months away
A pool that has been left running on its own for months, after a long trip, a season someone else was meant to cover, or a house you have just moved into, is not the same as one you closed. The water has drifted, the chlorine is probably gone, and the equipment may have been off. It is recoverable. Work in this order, and do not swim until the plan says the water is safe.
A morning to get it running, then about a week of test-and-dose rounds
When this applies
Your last test was months ago, or you have just taken over a pool you know nothing about.
If you closed the pool properly for winter, the opening checklist in Closing & opening your pool is the better guide.
- 1Look before you add anythingNote the colour of the water and whether you can see the floor. Clear, cloudy, green and dark green are four different starting points. Do not add anything yet.What you see decides the job. A green pool needs a clearing hold that runs for days, not one shock, and anything you pour in before the test changes the reading you are about to take.
- 2Get the equipment runningClear the skimmer and pump baskets, top the water up to mid-skimmer, and start the pump. Check for leaks, a pump that will not prime, or a filter pressure well above normal, and clean or backwash the filter if it is dirty.Nothing else works without circulation. A clogged filter is the usual reason a neglected pool stays cloudy after it has been treated.
- 3Check what you have storedLiquid chlorine loses strength in storage, faster in heat, so a jug that sat through a summer is weaker than its label says. Buy fresh. Test strips and reagents expire too: check the dates, and replace any that are past them or have been stored damp.The plan works out each dose from the strength printed on the label. Old chlorine under-doses, and an expired test gives readings the engine will believe.
- 4Circulate, then test everythingLet the pump mix the water for several hours, then log a full test: free and total chlorine, pH, alkalinity, calcium hardness and stabilizer, plus salt if you have a salt cell.Months change more than chlorine. Rain and top-ups dilute stabilizer and alkalinity, and evaporation concentrates calcium. Stabilizer sets your chlorine target, so the whole plan depends on that reading.
- 5Follow the plan in its orderIf the plan asks for a partial drain because stabilizer or calcium is too high, that comes first: a shock cannot work until the stabilizer is down. If it opens a clearing hold, keep it going until the overnight chlorine loss test passes, even after the water looks clear. Balance pH and alkalinity when the plan schedules them.A neglected pool often needs several jobs, and the order matters. The engine puts them in an order where one does not undo another.
- 6Expect a few rounds before it holdsRetest when the plan asks. Expect two or three test-and-dose rounds over the first week, and more if the pool was green.The first test shows where the water ended up. The next ones show how fast it uses chlorine, and that is what tells you it is healthy again.
When to call a professional
- The pump will not prime or run, the filter housing is cracked, or there is a leak at the equipment.
- The water level has dropped well below the skimmer and you do not know why. A pool losing water fast may have a leak or a damaged shell.
- The walls or floor show cracks, the liner has pulled away, or there is staining that does not brush off.
Once the pool holds its chlorine overnight and the readings sit in range, go back to a weekly test. The habit is what keeps you from having to do this again.
Where this comes from
- packages/chemistry-engine/src/recommendations/generateRecommendation.ts: a drain comes before any shock, and a clearing hold replaces a shock.
- packages/chemistry-engine/src/content/chemicalGuidance.ts and clearing/protocol.ts: the clearing hold and the overnight chlorine loss test that ends it (the trouble-free-pool clearing procedure).
- packages/content/src/seasonChecklists.ts: the opening checklist, for a pool that was closed properly.
Keep learning
How a water test worksA five-step, illustrated walkthrough from scooping a sample to getting your plan.How to add chemicalsThe safe, simple sequence for adding anything to your pool — animated step by step.Cloudy, green and what to do about itWhy pools go cloudy or green, what really clears them, clarifier versus flocculant, and how to read a pool store’s printout.What each measurement meansPlain-language explanations of every reading — what it measures and why it matters.What each chemical doesWhat every product does, how it’s added, and why the method matters.Choosing your chemicalsLiquid or powder, tabs or a salt cell, drops or strips — the real options for each job and the honest trade-offs of each.After you add chemicalsThe safety and comfort steps that follow any addition — and the reasoning behind them.Types of poolsPlaster, fiberglass, vinyl, tile, chlorine, saltwater — how each changes your routine.Pool equipment explainedPumps, filters, chlorinators, heaters, timers — what each part does for you.Closing & opening your poolThe two guided checklists that bookend the season — each step with its why.Protecting your pool from a freezeWhat to do when a freeze is forecast — four steps, ranked by the damage each one prevents.Draining part of your poolWhen a plan says to replace water: a quarter at a time, where the water can go, and when to stop and call a pro.How long to run the pump after you add somethingWhy the pump goes on before you pour, how long it stays on, and why the retest waits.Kids, pets and pool chemicalsStoring chemicals out of reach, keeping acid and chlorine apart, and who stays out of the water until the retest.Where our numbers come fromThe methodology behind every target and dose — the ratios, the caps, the rounding, and why AI reads but chemistry decides.