Winterising Your Pool: Australian Checklist for Closing for the Season

Unlike Northern Hemisphere pools that fully close for 5–6 months of frozen winter, most Australian pools run year-round. Water temperature in Sydney averages 18°C in July (peak winter); in Brisbane it stays above 20°C; in Melbourne it drops to 12°C; in Hobart to 8°C. Only in cooler climates does fully closing make sense.

This guide covers the autumn winterising routine for both approaches: running through winter (most of Australia) and fully closing the pool (Melbourne/Hobart/cool Adelaide).

Decide first: closing or running through?

Running-through-winter checklist (Sydney, Brisbane, Perth, etc.)

1. Reduce pump runtime

Summer typical: 8 hours/day. Winter: 4 hours/day is sufficient for most pools. Lower water temperature means slower chemistry, less UV demand, and lower bacterial load.

2. Reduce chlorinator output

For saltwater pools, reduce output to 20–30% (from 50–70% summer). Cell efficiency drops in cold water below 18°C anyway, running at high output wastes cell life.

3. Reduce sanitiser target (slightly)

FC targets can be reduced to the low end of the CYA-adjusted range. If your CYA is 60 ppm, summer target is 7 ppm, winter target can be 5 ppm. UV is weaker, bather load is zero or minimal.

4. Maintain pH and TA monthly

Winter pH drift is slower than summer drift, but still occurs. Test monthly, adjust as needed.

5. Cover the pool

A winter pool cover reduces evaporative loss, debris, and chemical demand. $300–$1,500 for a residential cover. Even if you don’t fully close the pool, a cover saves 50%+ on winter chemistry costs.

6. Check filter weekly

Winter debris (leaves, eucalyptus litter) loads filters faster than summer use. Backwash or clean weekly even with reduced pump runtime.

Full closure checklist (Hobart, cooler climates)

1. Balance chemistry first

Two weeks before closure:

• pH 7.4–7.6
• TA 100–120 ppm
• Calcium hardness 200–400 ppm
• CYA at your normal target
• FC at high end of normal range

2. Shock the pool

One week before closure, shock to break-point. Calculate target based on CYA (40% of CYA or 10× CC). This ensures pool is bacteria-free going into the dormant period.

3. Add winterising chemicals

Australian winter pool kit typically includes:

• Algaecide (polyquat-based, copper-free), prevents algae bloom during dormancy.
• Stain & scale preventer, prevents metal staining during low-flow months.
• Chlorine reserve, slow-dissolving cal-hypo or trichlor to maintain low FC throughout winter.

3. Lower water level

In freezing climates (rare in Australia, except for Hobart and cool highlands), lower water below the skimmer line. Prevents skimmer damage from ice expansion. Not needed in most Australian climates.

4. Disconnect or wind down equipment

• Drain pump and chlorinator (in freezing climates only).
• Disconnect heater.
• Disconnect salt cell from power.

5. Install winter cover

A full winter cover prevents debris, reduces chemistry load, and protects equipment. $400–$2,000 depending on size and quality.

6. Schedule monthly check-ups

Even closed pools need monthly visits, check chemistry hasn’t completely collapsed, top up with chlorine if needed, clear any major debris that’s gotten through.

What NOT to do

• Don’t drain the pool. Empty pools can crack from groundwater pressure or settling. Always leave water in.
• Don’t stop chemistry entirely. Pools left chemistry-free for 5 months come back as algae nightmares in spring.
• Don’t remove the salt cell. Keep it in place; just power down for winter.
• Don’t skip the cover. Even in mild Australian climates, a cover saves 30–50% of winter chemistry costs.