Winterizing Your Pool: A Chemical Guide
How to close your pool so you open to clear water in the spring.
Closing the pool is a sad day for any family, but doing it correctly is vital for protecting your investment. A poor winterization leads to cracked pipes, stained liners, and a 'swamp' opening in the spring that costs hundreds of dollars in chemicals to fix. The secret to a perfect opening is chemical balance and early closing. Let's walk through the professional chemical protocol for a long winter sleep.
The 'Wait for the Cold' Rule
The most common mistake is closing too early. Algae needs warmth and sunlight to grow. If you close your pool when the water is still 70°F, the chlorine will be gone in weeks, and algae will have all fall and spring to bloom under your cover. The golden rule: wait until the water temperature is consistently below 60°F (15°C) before putting the cover on.
Step 1: Balance the LSI
As water gets colder, it becomes more corrosive (LSI drops). To prevent the water from eating your plaster or metal parts over the winter, you should aim for a slightly positive LSI (+0.2 or +0.3) before closing. This usually involves raising your Calcium Hardness or Total Alkalinity slightly higher than your summer targets.
Step 2: Shock and Protect
Bring the pool up to 'Shock Level' (based on your CYA) 24 hours before closing. This ensures any organic matter is destroyed. Just before putting the cover on, add a high-quality polyquat algaecide. Avoid cheap 'copper-based' algaecides, as they can cause blue/green staining on your liner over the winter if the pH drifts.
Step 3: Plumbing and Antifreeze
For cold climates, blowing out the lines is the most critical mechanical step. Use a high-volume air blower to push all water out of the pipes and plug them at the pool end. Add non-toxic (pink) RV antifreeze to the lines for an extra layer of protection. A single frozen pipe can cost thousands to dig up and repair in the spring.
FAQ
Should I use a 'Winter Pill'?
Winter pills are slow-release clarifiers and enzymes. They can help keep the water clear, but they are no substitute for proper chlorine levels and a light-tight cover.
Do I need to drain my pool for winter?
Never drain a pool completely! The weight of the water is what keeps the pool in the ground. In many areas, an empty pool can 'float' or pop out of the ground due to hydrostatic pressure from the surrounding soil. Only lower the water level below the skimmers.
How do I deal with a mesh cover?
Mesh covers allow rain and snow to pass through, which also brings in dirt and leaches out chemicals. If you have a mesh cover, you will likely need to add a half-dose of liquid chlorine in the early spring (March/April) to keep the algae at bay until you fully open the pool.