You’ve pulled out the plugs, the antifreeze, and the winter cover, and you’re getting ready to close your pool just like last year. It’s a job that many pool owners do themselves, and it goes very smoothly when you know how to go about it.
But you can also make mistakes that will prove costly when you reopen the pool. The vast majority of damage discovered in the spring stems from water that’s been left behind somewhere—not from a forgotten product or incorrect dosing. Here’s what those mistakes are, what happens in each case, and the telltale signs to look for.
Why Trapped Water Is the Real Problem
Water expands when it freezes. Trapped inside a pipe, a pump housing, or a heat exchanger, it has nowhere to go, so it pushes against whatever is holding it in. The component gives way at its weakest point: a fitting, a housing, or a weld.
What makes this failure unique is that it isn’t visible in November. It’s discovered in early spring, when the system fills up and water leaks out through the crack. Six months pass between when these failures occur and when they’re discovered.
The Seven Most Common Mistakes
1. Closing a pool that is still dirty or out of balance
Whatever remains in the pool stays there all winter, without filtration, lighting, or supervision. An unbalanced pH continues to corrode the pool liner and metal parts for six months.
The sign: green or cloudy water when opened, even though it seemed “fine” when it was closed.
2. Overlooking a section of plumbing
This is the number one mistake. The main lines are usually handled properly, but there’s often a secondary line that remains full: an additional return line, a fountain supply line, a water heater line, or an automatic flushing circuit.
The sign: a leak that appears when the system is turned on in the spring, always in the same spot.
3. Failing to properly protect the pump or filter
Draining the basket isn’t enough. A pump housing retains water in its volute even after the drain plugs are opened, and a filter often retains water in its tank.
The sign: a crack in the pump housing or filter tank, visible only when pressure returns.
4. Using the wrong antifreeze
Automotive antifreeze has no place in a swimming pool. It is not designed for a recreational water system and does not behave the same way in pool piping. Pool antifreeze exists for this very reason.
The sign: startup water with an unusual color or odor, and a system that must be thoroughly flushed before use.
5. Neglecting the water heater and specialized equipment
A water heater contains a heat exchanger with many small passages, and each one can trap water. It is one of the most expensive components of a system, and one of the most susceptible to freezing. The same reasoning applies to a dosing pump, a salt system, or an automated chlorine treatment system [link to Automated Pool, Water Heater, or Dosing System: Should Your Winterization Process Be Different?].
The sign: a water heater that no longer heats up, or that leaks as soon as it’s turned back on.
6. Lowering the water level in the wrong place
The winter water level isn’t a one-size-fits-all value: it depends on the type of skimmer, the presence of return lines, and the type of cover installed. If the level is too high, water can reach the skimmer and freeze inside it. If it’s too low, the cover loses the support that holds it in place, and the liner may shift.
Signs: a wrinkled or peeling liner in the spring, or a cracked skimmer.
7. Installing the winter tarp incorrectly
A cover that’s too loose lets debris in, traps water in pockets, and puts strain on its anchor points. A cover that’s too tight rubs against the same anchor points all winter and eventually tears there.
The sign: standing water on the surface as early as November, or deformed anchors when opening the cover.
“With the covers we service, it’s almost never the product that’s at fault. It’s a step that was overlooked. People do the job right for the parts they’re familiar with, but they neglect a step that nobody mentioned when the pool was installed.” — Tristan Dufour, owner, Piscine Évolution
The Three-Point Checklist Before Covering the Pool
Before laying down the cover, ask yourself these three questions:
- Have I checked all the pipes? Count the visible openings in the pool (skimmers, return inlets, deep-well intakes, jets) and make sure each one corresponds to a line you’ve treated.
- Has every piece of equipment in the equipment room been drained? Pump, filter, water heater, treatment system—each one separately.
- Does the water level match my specific system? Not your neighbor’s, nor that shown in a generic video.
Frequently Asked Questions
Forgetting to drain a section of the plumbing. The main lines are usually blown out properly, but the secondary lines (water heater, jets, automatic cleaning system) are often overlooked, especially when the owner isn’t aware they exist.
Yes. Closing it while the water is still warm means letting it deteriorate under the cover for weeks before the cold weather sets in. It’s better to wait until the water stays consistently cold.
It is not required if the pipes are properly blown out and plugged, but it provides additional protection for sections that are difficult to drain completely. It never replaces the blowing-out process—it complements it.
Have it checked before the ground freezes. A full pipe spotted in November can still be fixed. The same pipe in January can no longer be fixed, and the problem won’t be discovered until spring.
What You Can Do Before Installing the Cover
Walk around your pool and count the openings. Then walk around the equipment room and count the units. If either number doesn’t match what you’ve accounted for, you’ve found your missing line.
A properly performed closure prevents unpleasant surprises in the spring. That’s what our closure service covers: adjusting the water level, flushing the pipes, winterizing the equipment, and installing the winter cover. Book your appointment before the first frosts, and if you book your spring opening at the same time, you could receive a 10% discount.et si vous réservez du même coup votre ouverture du printemps, vous pourriez bénéficier de 10 % de rabais.
