Opening Your Pool After Winter: Spring Restart Checklist

How your pool opens depends on what you did in autumn. A properly winterised pool with chemistry maintained, cover on, and monthly checks reopens in 2–3 days. A neglected pool with no winter chemistry reopens as a recovery project, typically 5–7 days to fully clear.

This guide covers both scenarios: the easy reopen, and the green-water recovery.

The easy reopen (well-winterised pool)

Day 1: Remove cover and inspect

1. Remove the winter cover. If wet/dirty, lay it flat in the sun to dry before storing.
2. Skim surface debris.
3. Brush walls, floor, steps, and corners. Pool brushes pick up the winter biofilm before chemistry has to.
4. Vacuum the pool floor if visible debris.
5. Check water level, top up if below skimmer line.

Day 1 (afternoon): Test and adjust

1. Test FC, pH, TA, CH, CYA.
2. FC will likely be low (winterising chemicals consumed). Top up to your normal CYA-adjusted target.
3. Adjust pH if needed, winter pH drift is usually toward high.
4. Run pump and check filter, backwash if pressure is elevated.

Day 2: Stabilise and verify

1. Re-test all parameters.
2. Verify FC is holding (didn’t disappear into a hidden algae bloom).
3. Add any additional chemicals needed to hit normal summer ranges.
4. Inspect salt cell (for saltwater pools), clean if it scaled up in winter.

Day 3: Ready to swim

Test once more, verify chemistry is stable, swim.

The green-water recovery (neglected pool)

The starting state

You remove the cover and find:

• Green water (algae bloom)
• FC at 0 ppm
• pH possibly drifted high
• Visible algae on walls and floor
• Debris that got under or around the cover

This is recoverable. Expect 5–7 days, $40–$100 in chemicals, and significant filter run-time.

Day 1: Major cleanup

1. Remove cover and skim heavy debris.
2. Test CYA (essential, sets the shock target).
3. Brush ALL surfaces aggressively. Algae biofilm needs physical disruption.
4. If pH is above 7.6, lower to 7.2.
5. Calculate shock dose: max(10 × CC, 40% of CYA). For typical green pool with CYA 50 ppm, shock target is 20 ppm.
6. Shock with liquid chlorine. Run pump 24 hours.

Day 2: Filter run + re-shock if needed

1. Backwash or clean filter (algae loads filters fast).
2. Test FC. Should still be near shock level. If dropped significantly (more than 4 ppm overnight), re-shock, algae is still actively consuming chlorine.
3. Continue pump 24/7.

Days 3–5: Sustained shock

1. Maintain FC at shock level until water clears.
2. Backwash filter daily.
3. Brush surfaces every other day.
4. Re-test daily.

Days 5–7: Recovery and verification

1. Once water is visibly clear, allow FC to drop to normal range.
2. Verify CC is below 0.5 ppm overnight, confirms algae is fully dead.
3. Test all parameters and adjust to normal ranges.
4. Final filter clean.
5. Verify CYA hasn’t been over-elevated from winter dichlor additions.

When to call a professional

If after 7 days the pool isn’t clearing:

• CYA is so high (above 150 ppm) that shocking is impractical, drain 50% and refill.
• Yellow/mustard algae instead of green, different species, needs specific treatment.
• Black algae visible on plaster, needs mechanical removal + multi-week treatment.
• Equipment isn’t working (pump won’t prime, filter won’t backwash).

The cost difference

The $50–$100 spent in autumn on proper winterising (algaecide, chlorine reserve, cover) saves $100–$200 of recovery cost in spring, plus 5+ days of pool unavailable for use.