As the leaves start to turn and that first chill creeps into the evening air, your backyard pool starts looking less like a refreshing oasis and more like a large, expensive bowl of water that needs some serious attention. The job of closing the pool for winter might feel intimidating, but it’s one of the most important things you can do to protect your investment. A little bit of elbow grease now will save you from a disaster come spring.

The single most important goal of winterizing is preventing freeze damage. Water expands when it freezes, and if it gets trapped inside your pool’s plumbing lines, filter, pump, or heater, that expansion can crack PVC pipes, split a pump housing, or ruin a thousand-dollar heater core. So, the whole process is basically about getting all that water out of the equipment and making sure nothing can get back in.

Before you start turning any valves, you need to get the water chemistry right. This is a step a lot of people skip, but it matters. You want to give the pool a good shock treatment and add a winterizing algaecide. The idea is to kill off any algae or bacteria that are hanging around. If you close the pool with living stuff in the water, you will open it to a green, slimy swamp in the spring. You also want to balance the pH, alkalinity, and calcium hardness. Balanced water is less corrosive to your pool’s surfaces and equipment. Run your filter pump for a full day after adding these chemicals to circulate everything thoroughly.

Now, it is time to get the water level down. You need to drop it below the skimmer mouth and the return jets. If you have a mesh winter cover, you usually drop the water about a foot below the skimmer. If you have a solid, water-tight cover, you might only need to drop it six inches. The reason is simple—you need to blow the water out of those lines, and you need to leave room for rain and snow melt that will sit on top of the cover without pushing water back into the skimmer.

This next part is the heart of the job: blowing out the lines. You will need a shop vacuum that can blow, or a proper air compressor. You connect the blower to the line you want to clear, typically starting with the skimmer line. Once you hear the air push the water out into the deep end, you quickly plug the skimmer opening in the pool wall with an expanding rubber plug or a gizmo. Then you do the same for each return jet line. It can be a two-person job—one person at the equipment pad controlling the air, and one person at the pool wall ready to slap the plug in as soon as the water stops. Don’t forget the line that runs to your pool cleaner if you have one.

If you have a heater, there is usually a drain plug or two on the manifold. You need to open those to let any water trickle out. Same goes for the pump. You unscrew the drain plugs on the pump housing and open the air relief valve on the filter. If you have a sand filter, you will want to turn the multiport valve to the “winter” position, which usually allows the sand to stay put but opens the internal passages to drain. For a cartridge filter, you simply pull the cartridge out, clean it, dry it, and store it away for the winter. Leave all these drain plugs out and store them in the pump basket so you don’t lose them.

Once all the equipment is drained, you can add antifreeze. This is a point of debate. The safest route is to use only pool-specific, non-toxic antifreeze. It is absolutely critical that you never use automotive antifreeze. That stuff is poison. Pool antifreeze is usually propylene glycol based, and it is safe for water. You pour a small amount into the skimmer and the return lines before you plug them. You also pour some into the pump basket and filter before you close those lids. The antifreeze provides an extra layer of insurance against a tiny amount of water left in a low spot that could freeze and crack a fitting.

Now you can put the winter cover on. Lay the cover across the pool, making sure it has a little slack in the middle. You need that slack to hold the water that will accumulate. Use water bags, cover clips, or cable-and-winch systems to hold it in place tight. A cover that is whipping in the winter wind will tear. Make sure all the bags are snug against the coping.

Finally, turn off the breaker to the pool pump at the main panel. You do not want it to accidentally turn on in the middle of January with all the drain plugs out. It would burn up the motor seal in seconds.

That is really the whole process. Go slow, be careful with the air pressure so you don’t blow a gasket, and label your plugs if you have to. If you get overwhelmed, there is no shame in hiring a professional. But if you are handy and pay attention to the details, closing your own pool is a satisfying weekend job that keeps your backyard ready for the first sunny day of spring.