Every fall, someone in every neighborhood drains their pool down as far as their pump will go, figures that’s the smart move, and then spends the following April dealing with a cracked skimmer, a shrunken liner, or – in the worst cases – a pool shell that shifted over winter. It’s one of the most common winterizing mistakes out there, and it’s completely avoidable once you know the right level.
The short answer: for most inground pools, leave the water level 4 to 6 inches below the bottom of the skimmer opening. For above-ground pools, never fully drain them – leave water within 3 to 4 inches of the return jet. The right level depends on your pool type, your cover type, and how hard your winters get. This article walks through each scenario with specific numbers so you’re not guessing.
Why Water Level at Closing Actually Matters
Water has two jobs in a closed pool: it keeps the structure stable, and it gives your winter cover something solid to rest on. Take too much out, and you lose both. The liner in a vinyl pool needs water pressure behind it to stay seated against the walls and floor. Without that pressure, especially in cold, dry conditions, vinyl contracts, pulls away from the bead track, and can crack. Fiberglass pools face a different risk – hydrostatic pressure from groundwater can literally push an empty or near-empty shell upward out of the ground. It’s not common, but it happens, and the repair bill is brutal.
Leave too much water in, and you create a different set of problems. Water sitting at or above the skimmer opening will enter the skimmer body. When that water freezes, it expands and can crack the skimmer housing or the surrounding concrete. A cracked skimmer is a mid-four-figures repair on most inground pools. Pool pros consistently flag this as one of the top causes of winterizing damage, and it’s entirely preventable with the right water level before you put the cover on.
Inground Pools: The Right Level by Cover Type
The type of cover you use changes the target water level significantly, because each cover handles rain, snow, and debris differently.
Solid Safety Covers and Standard Solid Covers
With a solid cover – whether it’s a cable-and-winch tarp or an anchored safety cover – water pools on top of the cover as snow melts and rain falls. That water has nowhere to go except into a cover pump. You need the cover to sit tight across the pool, and for that, you want water 4 to 6 inches below the bottom of the skimmer opening. This keeps the skimmer dry while still giving the cover enough support to hold its shape. Industry guidance from pool builders reinforces this 4-to-6-inch target as the standard for solid-cover installations.
Mesh Safety Covers
Mesh covers are breathable, meaning rain and snowmelt drip right through into the pool all winter. That’s actually a feature – no cover pump needed – but it means your pool water level will rise throughout the season. To account for that, start the season lower: 12 to 18 inches below the skimmer opening. If you go in at the standard 4 to 6 inches and get a wet winter, you’ll end up with water in the skimmer and a cover floating off its anchors. The extra headroom gives you margin. Water chemistry and level both shift throughout winter, and building in that buffer protects your closing work through the whole season.
Using a Skimmer Plug (Gizzmo or Equivalent)
If you install a skimmer plug – sometimes called a Gizzmo – inside the skimmer body before closing, it compresses as ice forms and protects the housing from cracking. With that protection in place, you can leave the water level at the tile line rather than dropping it to 4 to 6 inches below the skimmer. The cover sits higher, which some owners prefer. Just make sure the plug is rated for your skimmer size and installed snugly before you put the cover on.
Above-Ground Pools: Never Fully Drain Them
If you’ve ever wondered whether to drain your above-ground pool for winter, the answer is no – not completely, and not even close. The vinyl liner in an above-ground pool is held in place almost entirely by water weight. Drain the pool, and within days the liner will begin shrinking away from the walls, pulling out of the bead track at the top. By spring, you may be looking at a replacement liner. Leave the water level within 3 to 4 inches below the return jet fitting, install a proper above-ground winter cover, and let the water do its job of holding everything in place.
One exception: if your return jet sits very close to the waterline, some owners drop the level just past the jet so they can install a winter plug in the fitting without water pouring out. That’s fine – you’re still leaving the vast majority of water in the pool. What you’re not doing is dropping it down 12 inches or more. Keeping liner pools adequately filled through winter is a consistent recommendation from pool service professionals across climates.
Climate Adjustments: Mild vs Hard Freeze Zones
The target levels above assume a typical cold-climate winter. If you’re in a zone that rarely freezes – USDA zones 9 and 10, roughly – you have more flexibility. Pools in mild climates often overwinter with the water level at normal operating range (middle of the skimmer opening) because freeze risk is low and the pool is sometimes used year-round. The main reason to drop the level at all is to clear the skimmer before a potential cold snap.
In hard freeze zones – anywhere that sees sustained temperatures below 20 degrees Fahrenheit – the 4-to-6-inch rule becomes more critical, not less. Frozen water expands with about 9% more volume than liquid water, and that expansion is what cracks concrete, PVC fittings, and skimmer housings. If you’re already blowing out your lines with a compressor (which you should be in hard freeze zones), the water level drop also ensures your return lines are above the frost line when you plug them. Your plumbing company or a step-by-step closing guide from a local pool service can confirm the frost depth in your specific area.
A Worked Example: 18×36 Inground Vinyl Liner Pool
Say you have an 18×36-foot inground vinyl liner pool with a single skimmer, a solid safety cover, and winters that regularly drop to 15 degrees Fahrenheit. Here’s what your closing water level looks like:
- Locate the skimmer opening – measure from the waterline down to the bottom edge of the skimmer faceplate.
- Drop the water 4 to 6 inches below that point – for a skimmer faceplate sitting at the waterline, you’re looking at about 4 to 6 inches of drop total from normal operating level.
- Install a skimmer plug – even at this level, adding a skimmer plug costs about $5 to $15 and gives you an extra layer of freeze protection.
- Install your solid safety cover – it should sit taut across the surface with the water providing support from below.
- Place a cover pump – set it to auto so it handles rain and snowmelt accumulation on top of the cover through winter.
Total water removed from a pool that size to drop the level 5 inches: roughly 170 gallons. That’s it. You’re not draining the pool. You’re lowering it by about 5% of total volume.
Mistakes to Avoid Before You Cover Up
Getting the water level right is only part of a solid closing. A few other things that go wrong at this stage:
- Skipping the chemical balance: Water that goes into winter with unbalanced pH or low sanitizer will come out green and corrosive. Balance the water before dropping the level, not after. AquaDoc’s winterizing shock is one option pool owners use to get a clean chemistry baseline before the cover goes on.
- Leaving return fittings open: Once you’ve dropped the level and blown the lines, plug every return fitting before you add the cover. An open fitting is an invitation for debris and critters.
- Forgetting the cover condition: A cover full of holes or fraying straps won’t protect the water you worked to balance. If your cover has seen better days, it’s worth replacing it before closing. If you want a reality check on what a neglected cover can look like come spring, the post on what accumulates in a winter pool cover is sobering reading.
- Ignoring the water line tile: If you have tile at the waterline, leaving water right at the tile line without a skimmer plug means ice can form directly against the tile and grout. Drop it below the tile or use a plug.
And if you’re closing a pool that came out of the season with a stubborn green tint, sort that out before you cover it. Water that goes in green comes out worse – read through the causes and fixes for that green tint before you button things up for winter.
Frequently Asked Questions
How much water should you leave in an inground pool for winter?
For most inground pools with a solid or mesh cover, leave the water level 4 to 6 inches below the skimmer opening – roughly at the bottom of the skimmer faceplate. If you use a skimmer plug or skimmer cover, you can leave the level at the bottom of the tile line instead, which gives the cover more support across the surface.
Should you drain an above-ground pool for winter?
Never fully drain an above-ground pool for winter. Without the weight of the water holding the liner against the walls, the liner will shrink, shift, or pull out of the bead track entirely. Leave it full, or within 3 to 4 inches below the return jet, and cover it with a properly fitted winter cover.
How low should pool water be for a mesh winter cover?
With a mesh cover, keep the water level 12 to 18 inches below the skimmer opening. Mesh covers allow rain and snowmelt to pass through, so the extra headroom prevents accumulating water from floating the cover off its anchors or flooding the skimmer throughout the season.
Can you leave pool water level at the tile line over winter?
Yes, but only if you have a skimmer plug installed and a freeze-proof closing setup. At the tile line, water is still sitting in the skimmer body, which can crack when it freezes. If you use a proper skimmer plug, the tile-line level is fine. Without that protection, keep water 4 to 6 inches below the skimmer.
What happens if you drain your pool too low for winter?
Draining an inground pool too low – more than 12 to 18 inches below the skimmer – risks hydrostatic pressure lifting the shell, especially in clay-heavy or high-water-table soils. For vinyl liner pools, low water allows the liner to dry out, shrink, and crack. Some fiberglass pools have been known to float partially out of the ground when emptied in wet conditions.
The bottom line: leave the water in. Drop it 4 to 6 inches below the skimmer for a solid cover, 12 to 18 inches for a mesh cover, and never drain an above-ground pool past the return fitting. That one decision protects your liner, your skimmer, and your shell through every freeze-thaw cycle until spring.