When the nights start dropping toward freezing and the leaves pile up on your pool cover, you know closing day is close. An above-ground pool is a wonderful thing in July, but it needs a thoughtful shutdown to come through a cold winter in good shape. Done well, closing takes a weekend. Done in a hurry, it can mean a stained liner, a cloudy green pond, and a long list of spring repairs.
This guide walks through the whole process in the order you will actually do it: timing, supplies, water chemistry, water level, equipment, the cover, and the checks you make during the winter. The steps apply to most round and oval above-ground pools. Your manufacturer’s manual always has the final word on details for your specific model, so keep it handy while you work.
Why Closing an Above-Ground Pool Takes Care
Cold climates put a pool through several kinds of stress at once. Water can freeze and expand, snow and ice add weight to the cover, and a pool that is left with unbalanced water grows algae even under a cover, because winter days can still warm up enough to wake it up. A good closing deals with all three problems before they begin.
The good news is that above-ground pools are straightforward to close. In most cases the pool stays filled, and the pool is “closed” by covering the filled pool with a tough winter cover made of durable plastic. That simple idea is the heart of the job. Everything else you do, from cleaning to balancing to draining lines, is preparation to make sure that cover is protecting clean, balanced water and a healthy set of equipment.
Picking the Right Time to Close
Many pool owners close once the water temperature settles consistently below about the point where algae slows down. A simple rule of thumb is to watch the weather rather than the calendar. When daytime highs stay cool and overnight lows are regularly near freezing, it is time to plan your closing weekend.
Closing a little early is usually kinder to your pool than closing late. Leaves and debris that fall into an open pool break down and add nutrients to the water, and the cleanup in spring gets harder with every week they sit. If you have trees near the pool, aim to close shortly after most of the leaves have come down, and use a skimmer net each day until then.
Pick a dry day with little wind. Pulling a cover across a pool in a gust is a two person job at best, and a calm day makes every step easier.
Gathering Your Winterizing Supplies
Having everything on hand before you begin keeps the job smooth. A basic checklist looks like this:
- A winter pool cover sized for your pool, made of heavy duty material
- Winterizing chemical kit or the individual chemicals recommended for your pool size
- Test kit or test strips, including pH and alkalinity
- Pool brush, vacuum, and skimmer net
- Cover clips, cable and winch, or the fastening system that matches your cover
- An air pillow, if your manufacturer recommends one
- Winterizing plugs for return and skimmer openings
- A submersible pump or siphon for lowering the water level
- Towels and a bucket for equipment drainage
Most local pool supply shops carry all of these. If you are new to closing, ask the staff which chemicals suit the type of sanitizer you ran all summer, since chlorine, saltwater, and other systems have slightly different needs.
Cleaning the Pool Before You Cover It
A cover goes onto a clean pool. Skim the surface, brush the walls and floor, and vacuum up whatever settled on the bottom. Brushing matters because algae spores and film cling to the liner, and months under a cover give them time to grow.
Empty the skimmer basket and the pump basket, and clean or backwash the filter according to the type you have. A sand filter can be backwashed, a cartridge filter should be removed and rinsed thoroughly, and a diatomaceous earth filter needs its grids cleaned. Whatever filter you run, finish this step before you drain or store anything, since a dirty filter sitting through winter becomes a smelly chore in spring.
Balancing the Water Chemistry
Water chemistry is the part many owners skip, and it is the part that most affects what you see in April. Test the water a few days before closing so you have time to adjust it. The usual targets are a pH in the neutral to slightly basic range, total alkalinity within the range your manufacturer or chemical supplier suggests, and calcium hardness that is not too low for your liner and metal parts.
Adjust alkalinity first, then pH, because alkalinity influences how stable the pH will be. Retest after each adjustment and give the pump time to circulate the water. Taking the extra day to get the numbers right is much easier than treating a pool that closed out of balance.
Shocking and Adding Winterizing Chemicals
After the water is balanced, shock the pool to clear out organic contaminants. Run the pump overnight so the shock circulates, and wait until the chlorine level drops back into a normal range before adding your winterizing chemicals. Adding algae preventer on top of very high chlorine can reduce its effect, so patience pays off.
A winterizing kit typically includes a shock, an algaecide made for long term use, and sometimes a stain and scale preventer. Follow the dose on the label for your pool’s volume. If you are not sure how many gallons your pool holds, the manual or the original paperwork will have the figure, and a quick calculation from the diameter and average depth gives a close estimate.
Pour chemicals in with the pump running and let it circulate for several hours, so the products distribute evenly before you shut the system down.
Lowering the Water Level Correctly
Water level is a place where above-ground pools differ from in-ground ones, and where owners most often have questions. The pool stays filled for winter because the water helps hold the liner against the wall and supports the structure. You still need to lower the level a bit, so rain and melting snow have room, and so water does not sit at the skimmer opening where it can freeze and damage the faceplate.
Check what your manufacturer specifies. Many call for the level to sit a few inches below the bottom of the skimmer opening. Some pools with a cover sealed to the skimmer use a different method. Whichever applies to you, lower the water slowly with a submersible pump or siphon, and stop once you reach the recommended mark. Draining too much is a mistake, because a liner without enough water behind it can slip, wrinkle, or shrink in the cold.
Draining and Protecting the Equipment
The pump, filter, heater, and hoses all hold water that can freeze and crack housings. After you lower the pool level, shut off the power at the breaker and drain each piece of equipment fully. Remove the drain plugs on the pump and filter, take off the hoses, and let everything dry before storing it in a protected place, such as a garage or basement.
Blow out or drain the lines running to the pool as your system requires, then seal the openings with winterizing plugs. If you have a saltwater system, remove the salt cell, rinse it, and store it indoors according to the maker’s directions, since the cell is a valuable part. Store the ladder or steps as well. Many ladders can be unbolted and stored, and lifting them out also keeps them from damaging the cover.
Label hoses and keep the small parts such as plugs, gaskets, and clamps in one bag. In spring you will be glad you did.
Using an Air Pillow and Protecting the Walls
An air pillow is a large inflatable cushion that sits in the middle of the pool beneath the cover. It lifts the center of the cover so snow and meltwater run toward the edges and so expanding ice has a bit of room. Many manufacturers recommend one for above-ground pools, and they cost little compared with the hardware they help protect. Inflate it partly, not fully, so it can flex as the cover loads with snow and temperatures change.
Tie the pillow to a ladder anchor or another secure point, so it stays centered, and make sure the cover can lie over it without strain. If your pool has top rails or a top seat, check them for sharp edges that could tear the cover, and wrap those spots in soft padding or tape.
Installing the Winter Cover
The cover is the main event, so give it your attention. Unfold it beside the pool and drag it across the water in an even motion. Center it and make sure the overhang is equal all the way around. Wrinkles and pockets collect water and snow, so smooth them out where you can.
Secure the cover tightly using the system designed for your pool, such as a cable and winch run through the cover’s grommets, or clips along the top rail. Tighten the cable until the cover sits snug against the wall with no big gaps where wind can lift it. A loose cover flaps in storms, wears out faster, and can let leaves fall inside. Many owners also add wall bags or covers weights as recommended, in line with the cover manufacturer’s advice.
Some owners like to place the cover over the pool with a small amount of water on top, but heavy buildup is a concern, so use a cover pump when water or melting snow collects on the cover.
Special Notes for Hybrid and Partly Buried Pools
Not every above-ground pool sits entirely above the ground. Hybrid designs from radiant pools, for example, use a heavy walled structure that can sit fully above grade or partly buried into the slope of a yard. This gives installers flexibility on sloped or uneven properties without extensive excavation or site leveling.
The closing steps are the same for the most part, since the pool is still filled and covered. The difference is in the details. Soil pressing on a partly buried wall helps support it, so keep the water level in line with the manufacturer’s guidance for your model. Pay extra attention to drainage around the pool, because water pooling next to a partly buried wall in spring can cause trouble. If you are not sure how your particular pool should be winterized, contact the company that installed it, since they know the product and your site.
Checking on the Pool During Winter
A closed pool does not need daily attention, but it rewards the occasional look. After a heavy snowfall or a storm, walk around the pool and check that the cover is still snug and the cable is still tight. Do not climb on the cover or use sharp tools to clear it, and avoid pulling on it from the edge.
If water collects on top, remove it with a cover pump. If snow piles up deeply, use a soft push broom with a long handle, and brush gently from the edges. Keep ice and debris off the wall, and watch for any sign that the water level under the cover has dropped a great deal, since that could point to a leak that is better found in January than in May.
Safety and Local Rules Around Closed Pools
A covered pool still needs to be safe. Keep children and pets away from the cover, because a standard winter cover is not made to hold weight. Keep any ladder or access point removed or locked, so no one can climb into the pool area.
Regulations differ from town to town. Many towns have fewer fence and safety cover requirements for above-ground pools than for in-ground pools, but you should always check your own town or city ordinances before installing or changing anything about your pool setup. Your local building or town office can tell you what applies.
Planning Ahead if You Are Still Choosing a Pool
If you are reading this because you are thinking about adding a pool next year, the closing routine is a useful thing to consider. An above-ground pool has a smaller footprint, usually needs less excavation, and the winter routine is manageable for a homeowner with a free weekend. Comparing options is easier when you can see them, and browsing these swimming pools in New Hampshire is one way to see how above-ground, in-ground, and salt water choices stack up before you decide.
It also helps to talk with someone who works with pools through the whole year. A local New Hampshire pool company can walk you through what closing, maintenance, and opening look like for the pool you are considering, so there are no surprises when the first cold snap arrives.
A Simple Closing Day Checklist
When closing day arrives, it helps to work from a short list. Here is the order that tends to work best:
- Skim, brush, and vacuum the pool, and clean the baskets and filter.
- Test and balance alkalinity, then pH, and check calcium hardness.
- Shock the pool, run the pump, and wait for chlorine to settle.
- Add winterizing chemicals and circulate them for several hours.
- Lower the water level to the mark your manufacturer recommends.
- Turn off power, drain the equipment, and seal the lines with plugs.
- Remove the ladder, store the salt cell if you have one, and gather small parts.
- Set the air pillow, pad any sharp edges, and install the cover snugly.
Running through the list in order keeps the job from feeling like a scramble, and it makes it easier to hand off a step to a helper without losing track of what is done.
Common Closing Mistakes to Avoid
A few errors come up again and again. One is closing with chemistry out of balance, which invites algae and staining. Another is draining too much water, which can leave the liner unsupported. A third is leaving water in the pump or filter, which can crack parts that are expensive to replace.
Cover problems are the fourth category: a cover that is too small, a cable left loose, or a cover that is never cleared of standing water. Most of these are easy to avoid with a little time and a checklist, and they are the best reasons to work through each step instead of rushing to finish.
Looking Ahead to Spring Opening
The work you do now sets up opening day. A clean pool, balanced water, and tidy equipment mean a quicker start when warm weather returns. When the time comes, clear the cover, remove it carefully, and clean and store it dry. Reinstall the equipment, refill the pool to its normal level, test the water, and shock it before you swim.
If your cover and gear are in good shape after winter, you will know your closing method worked. Make notes on what went well and what you would change, and tape them inside your pool equipment bin. Next fall, the process will go even faster, and your pool will be ready for another long season.
