Opening your pool: from the easy wake-up to brown water
- Golden rule: reopen BEFORE the water climbs back above ~12 °C — after that, the algae have a head start.
- Standard wake-up: reassembly, cleaning, long filtration, full test, rebalancing, shock if needed.
- Brown water under the cover = often metals: SEQUESTER BEFORE chlorinating, or it gets worse.
- The app generates a reopening plan matched to your water's actual state, brown water case included.
The spring opening is winterising’s moment of truth — and the most profitable race of the year: run well and on time, it spares you weeks of catch-up. The golden rule fits in one sentence: reopen before the water climbs back above ~12 °C. Below that, the algae are still asleep and the wake-up is a formality; above it, they’re already off the starting blocks. After that, everything depends on what you find under the cover: clear water (standard wake-up), green water (classic rescue), or the trap — brown water, where the first instinct (chlorinate) is exactly the wrong one. The CliniPool app generates a plan matched to your water’s actual state.
The standard wake-up
If the winterising was done by the book, the sequence is mechanical — follow the step-by-step guide above: uncover, refill the circuit, clean thoroughly, filter at length, test, rebalance. Two tips from experience: start with the long filtration before judging the water (water that’s sat still for months always looks worse than it is), and do the full test only after that mixing — testing unmixed water gives fantasy numbers.
Green water at opening
A cover that wasn’t quite opaque, a slightly late winterising, an early warm spell: the springtime pond is the great classic. No panic and no draining — it’s a standard green water rescue: serious mechanical cleaning, pH corrected, a shock dosed on your actual readings, continuous filtration, 2 to 5 days of patience. The full green water guide (“Also worth reading”) details every step, and the app’s guided plan chains them together with timers.
The trap: brown water
Brown, rusty or tea-coloured water when the cover comes off tells a different story: dissolved metals (iron, manganese — well water, winter top-ups, ageing equipment), sometimes mixed with organic matter. And here, instinct betrays you: chlorinating iron-rich water makes it worse — chlorine oxidises the iron, deepens the colour and can stain the liner for good.
The right order is counter-intuitive but simple: sequestrant first, chlorine second. Neutralise the metals (pH towards the low end, sequestrant dosed to the volume), filter at length, and only then bring the sanitisation back up, gradually. It’s precisely the scenario for which the app has a dedicated “brown water opening” plan — it runs the sequence in the right order, doses calculated.
The smart bonus: the start-of-season check-up
The opening is THE right moment to measure what nobody ever looks at: the stabiliser (did it cross a critical threshold after last season? now is when a partial dilution costs the least) and the hardness (winter top-up water may have changed the picture). Five minutes of tests that set the course for the whole season — the app folds them into its opening check-up and saves you from discovering the problem in August.
Frequently asked questions
When should you reopen your pool in spring?
Before the water stays above ~12 °C. Reopen early = water still "asleep", minimal catch-up. Reopen in May with water at 18 °C = algae already at work for weeks.
My pool is green at opening — is that bad?
No, it's the most common scenario after a late winterising or a non-opaque cover. It's a classic green water rescue: cleaning, pH, calculated shock, continuous filtration. Allow 2 to 5 days.
Why did my water turn BROWN after the first chlorine of the season?
Dissolved iron (well water, winter top-ups, equipment) was oxidised by the chlorine and became visible. Stop chlorinating and go through a sequestrant — continuing to chlorinate deepens the colour and risks staining.
Should I drain the pool to start from a clean slate?
Almost never: even badly degraded water can be rescued chemically, and a full drain has its own risks (structure, groundwater). PARTIAL water changes, though, are useful — notably to dilute a stabiliser that's too high.