How Far Below the Skimmer Do You Winterize a Pool? A Comprehensive Guide

Winterizing your swimming pool is one of the most critical steps in extending its life and maintaining water quality during the off-season. However, one of the most frequently asked questions by pool owners, particularly in colder climates, is: how far below the skimmer should you lower the water level during winterization?

This article explores everything you need to know about winterizing a pool, the importance of water level positioning relative to the skimmer, and the best practices for different types of pools. Whether you have an in-ground or above-ground swimming pool, understanding proper winterization will save you money, prevent damage, and ensure your pool is ready to go when summer arrives.

Why the Water Level Matters During Pool Winterization

Before we dive into exactly how far to lower the water level, it’s essential to understand why this question even matters. During the winter, freezing temperatures can wreak havoc on a pool’s structure, especially if the water is not properly managed. Water in pipes, jets, or the pool basin expands when it freezes, which can lead to cracked tiles, damaged pumps, or even structural failure.

Here’s why the skimmer’s location is significant:

• Water level affects freeze damage: If the water is too high and freezes, ice expansion can crack the skimmer or surrounding tile work.
• Water level impacts plumbing protection: Lowering the water appropriately allows for proper blowing out of lines below the skimmer’s mouth, preventing freeze-related damage.
• Diverse pool types have different requirements: Vinyl, fiberglass, and concrete pools have unique winterization needs.

How Far Below the Skimmer Should the Water Level Be?

Generally, when winterizing an in-ground pool, you should lower the water level about 6 to 8 inches below the skimmer. This depth ensures:

• That the skimmer isn’t at risk from freezing water expansion.
• Equally, the pool’s main drain remains submerged.

Let’s break down this answer into more specifics.

What Does “Below the Skimmer” Mean Exactly?

The skimmer is the rectangular opening on the pool wall that draws water into the filtration system. The top edge of the skimmer is where you usually expect the normal water level to sit during the swimming season.

To winterize, you’re aiming to bring the water level below the skimmer’s mouth, which is actually a few inches below the pool wall’s lip.

If you’re unsure where the skimmer’s mouth begins, it’s usually just below the round or rectangular slot, just where the water flows into the skimmer basket.

Why 6-8 Inches Specifically?

1. Ice expansion room: By dropping the pool water level, you allow space for a potential ice sheet to form without pushing up against the skimmer or tile line.
2. Pump and filter safety: Lowering the water enables technicians or DIYers to blow out all the lines below the skimmer opening, ensuring no water pockets in the plumbing cause freeze damage.
3. Protection of coping and tile: Tile damage is common when water freezes in the skimmer mouth. A lowered water level prevents this.

Special Considerations by Pool Type

The general rule of thumb—6 to 8 inches below the skimmer—is most directly applicable to traditional in-ground concrete (plaster) pools. However, alternative pool constructions, such as vinyl and fiberglass, require slightly different handling.

Vinyl Liner Pools

Vinyl liner pools are especially sensitive to freezing conditions because the liner can tear or stretch under pressure.

For these, it’s advised to lower the water to:

• 3–6 inches below the skimmer (not as low as concrete pools).

Why the difference?

Vinyl liners can collapse or wrinkle if the water level drops significantly. The presence of a solid winter cover and equalizer line can help maintain liner shape while allowing for safe water levels.

Fiberglass Pools

Fiberglass pools are resilient but still require proper winterizing, particularly during extended freezes.

Water levels in fiberglass pools should be:

• 6–8 inches below the skimmer—similar to concrete pools.

Fiberglass pools are not prone to cracking due to freeze-thaw cycles the same way plaster pools are. However, the plumbing, skimmer, and tile still require protection.

Above-Ground Pools

Above-ground pools have seasonal disassembly as part of the routine, especially in cold zones. Since most owners drain the pool entirely, the “how far” question doesn’t directly apply.

However, if you intend to keep an above-ground pool standing through winter:

• Do not drain entirely: Maintain some water in the pool—about halfway up the skimmer—or risk collapse.
• If winterized by lowering water level, drop the level to 2–4 inches below the skimmer intake to avoid freezing damage.

Winterization Steps for Maximum Protection

Knowing how far to lower the water level is only one piece of the puzzle. A complete and effective winterization includes several crucial steps:

1. Test and balance the water: Do a full water chemistry analysis and adjust pH, alkalinity, calcium hardness, and chlorine levels before closing.
2. Clean the pool thoroughly: Brush, vacuum, and skim debris. Use algaecide to prevent algae growth during winter dormancy.
3. Lower water to the proper level: As discussed, 6–8 inches below the skimmer for most in-ground pools.
4. Remove and store equipment: Take out ladders, diving boards, and skimmer baskets. Drain pumps, filters, and heaters.
5. Winterize the plumbing: Use a pool air compressor or professional-grade blower to push water from lines. Install winter plugs in return jets and skimmers.
6. Install a winter cover: Secure either a mesh or solid cover tightly. For vinyl pools, an equalizer tube can prevent debris from concentrating and damaging the liner.
7. Use water bags or anti-ice devices (optional): Some pool owners float winter pool bags near the center of the pool to prevent a solid ice sheet from forming and minimizing expansion damage.

Common Mistakes When Lowering Water Levels

Even experienced pool owners might make errors during winterization. Here are the most common mistakes regarding how much water to drain:

The Role of the Skimmer in Pool Winterization

The skimmer may seem like a simple structure, but it plays a major role in winterizing procedures.

Where to Place the Skimmer Plug

When the water level is lowered, a common step is to insert a skimmer plug into the skimmer mouth to prevent water from re-entering the pipe system. However, some pool professionals choose not to plug the skimmer if the water is lowered enough that the pipe remains below the water level at all times.

Pro Tip: Using a skimmer plug can be a double-edged sword—it often helps prevent debris and freezing water from entering the line, but it can also create a seal that holds residual water, which could freeze and expand inside the skimmer. Make sure the plug is compatible and the line is fully dry before sealing shut.

Skimmer Mouth vs. Skimmer Basket

Sometimes pool owners confuse the skimmer mouth (the opening in the wall) with the skimmer basket (the plastic container inside). Winterization steps relate to the mouth position, not the basket, which is best removed entirely for winter.

Winterizing Above and Below the Waterline

Proper winterizing doesn’t only cover what happens below the skimmer and waterline—it also involves protecting elements above the water.

Tile and Coping Protection

Water left at improper levels can cause ice to form along the inside edge of the coping (the border around the pool’s edge). This can lift or crack the coping stones and even damage the tile.

To prevent this:

• Check that no standing water remains in the skimmer throat after drainage.
• Ensure tile edges are clean and free of calcium buildup before closing the pool.
• Use anti-scaling agents to reduce tile staining during the off-season.

Winter Covers and Water Accumulation

Even with a proper water level, the pool cover can hold water if not installed properly. Rain or snow can accumulate on the cover surface, putting pressure on the skimmer and the pool walls.

To avoid this:

• Use a mesh cover if you’re in a heavy-rainfall zone.
• Keep a water bag system off-center so snowmelt or rain drains to one area.
• Inspect covers regularly during winter and pump off standing rainwater.

Regional Variance: Climate Considerations When Winterizing

The climate where your pool is located plays a massive role in how you approach winterizing. Pools in warmer regions like Texas or Georgia often only need to be superficially winterized, while pools in colder states such as New York or Michigan must be fully closed with drastic water level reductions.

Deep Freeze Zones

In zones where deep freezing is common (below 20°F or -6.6°C):

• Lower water to at least 8 inches below the skimmer mouth.
• Use air compressors to remove all excess water from plumbing.
• Consider using Skimmed Ice Guard Devices, which float ice toward return jets to reduce pressure on the pool walls.

Mild Winter Zones

In areas where freezing is occasional rather than prolonged or severe:

• A drop of 3–6 inches below the skimmer may suffice.
• Skimmer vacuum plugs may not be necessary if the return lines are submerged and freeze protection devices are in place.

How to Drain the Pool to the Proper Level

Draining your pool to the recommended 6–8 inches below the skimmer isn’t always as straightforward as it sounds. Pool owners use various methods depending on time, equipment, and urgency.

Using a Submersible Pump

A submersible pool pump is one of the quickest and most effective ways to lower water levels precisely.

Step-by-step:

1. Place the submersible pump at the deep end of the pool.
2. Turn on and direct the hose output to a safe drainage point away from the home and pool structure.
3. Monitor water level using a pool pole with a visible mark.
4. Turn off pump once you reach the 6–8 inch mark.

Utilizing the Pool Filter’s Waste Line

If your filter has a multiport valve with a “waste” setting:

• Set the valve to waste.
• Allow water to exit the pool through the backwash line, bypassing the filter.
• Use a long stick or pole to measure how low the water has dropped.

This method takes longer but causes less mess than using a submersible pump.

Manual Removal

For small water level reductions:

• Use a bucket to manually remove water.

This is labor-intensive but practical when using natural evaporation or minor drainage adjustment.

Final Tips for a Successful Pool Winterization

Successful winterization depends on more than just lowering the water level correctly—it’s a blend of chemistry, mechanics, and preparation.

• Start early: Begin your winterization two to three weeks before freezing temperatures hit.
• Schedule a professional: If you live in a freezing zone, have a pool expert verify the plumbing winterization, especially skimmer lines and main drains.
• Document your process: Take photos or notes of skimmer levels and equipment settings so you can make adjustments each year based on results.

Conclusion

Knowing the correct water level to winterize a pool—typically 6 to 8 inches below the skimmer edge—is crucial to protecting your investment and extending your pool’s lifespan. Whether you own a vinyl, fiberglass, or concrete pool, following local climate conditions and adopting a holistic winterizing strategy can help maintain water quality and prevent costly damage.

Armed with the right tools and knowledge, you’ll be confident that your pool will survive the winter intact and be ready to open smoothly again in the spring season.

Remember, the skimmer isn’t just a filtration tool—it plays a central role in winter prep. Give it the care and attention it deserves, and it will ensure your pool is there for you year after year.

Why is it important to winterize a pool below the skimmer?

Properly winterizing a pool below the skimmer is essential to prevent water from freezing in the plumbing lines, which can lead to costly damage such as cracked pipes or a malfunctioning filtration system. When water freezes, it expands, and any standing water in these lines can cause serious structural issues. By lowering the water level below the skimmer, you help ensure that no water remains trapped in these components, reducing the risk of winter-related damage.

Additionally, winterizing below the skimmer helps protect the pool’s equipment, such as the pump, filter, and heater, by allowing them to be properly drained and stored. This process also aids in maintaining water chemistry throughout the winter months, as a lower water level reduces the chance of debris buildup and algae growth. Taking the time to properly winterize this part of your pool can extend the lifespan of your pool equipment and reduce maintenance work in the spring.

How far below the skimmer should I lower the pool water level?

The general recommendation is to lower the pool water level to about 3 to 6 inches below the skimmer opening. This depth is typically sufficient to ensure that the skimmer and its inlet are no longer submerged, preventing water from settling and freezing inside the plumbing lines. The exact distance may vary slightly depending on your pool type and local climate conditions, particularly whether you expect heavy snowfall.

If you live in a region with harsh winters and prolonged freezing temperatures, it may be wise to lower the water level a bit further, especially if the pool features additional features like automatic cleaners or secondary inlets. However, avoid draining the pool too much—doing so can cause structural problems, especially in vinyl or fiberglass pools, which can shift or suffer damage if left empty.

Can I use a pool cover without lowering the water below the skimmer?

While it is technically possible to cover a pool without lowering the water level below the skimmer, it is not advisable. If the water is not lowered and the pool cover is installed tightly, freezing temperatures can cause the water to expand inside the skimmer and pipes, leading to cracks and expensive repairs. A rigid or floating cover can exacerbate the issue if pressure is applied unevenly.

By properly winterizing the water level below the skimmer, you give yourself the option to use either a mesh or solid winter cover effectively. Solid covers, in particular, can catch water and debris, and having the correct water level provides enough space to safely pump off any accumulated water without overloading the pool. Skipping this step could also void equipment warranties and damage the pool structure.

What tools are needed to winterize the skimmer and return lines?

To properly winterize the skimmer and return lines, you’ll typically need a few key tools: a submersible pump or the pool’s own pump, a shop vac or air compressor, winterizing plugs, skimmer covers or caps, and possibly antifreeze if you opt for a wet method of winterization. These tools help you drain lines effectively and prevent freezing damage. An adjustable wrench and screwdriver are also useful for removing drain plugs and covers.

For the skimmer, you will usually install a skimmer guard or cover to seal off the opening and protect the interior from debris and freezing temperatures. Using compressed air to blow out the lines ensures that no standing water remains that could freeze and expand. If using antifreeze, be sure to use pool-rated, non-toxic kinds, and pour them into the skimmer and return jets after draining. Each method has specific steps, and choosing the right tools makes the process more efficient and effective.

What are the consequences of not winterizing a pool correctly?

Failing to winterize a pool correctly can lead to significant problems such as cracked tiles, damaged skimmers, and burst pipes. When water freezes inside the plumbing system, especially near the skimmer or filter lines, the pressure can cause irreversible damage that often requires expensive repairs. Additionally, improperly winterized pools may suffer from algae growth or chemical imbalance, which makes reopening the pool more difficult and time-consuming.

In regions where freezing temperatures are common, not winterizing can also affect pool equipment like the pump and filter, which could seize or rust during the off-season. Moreover, improper winter preparation might invalidate manufacturer warranties on your pool components. In-ground pools may see structural damage from freezing and thawing cycles, particularly in vinyl or fiberglass models, while above-ground pools could lose their shape or develop rusted supports.

Should I remove the skimmer basket before winterizing?

Yes, it’s important to remove the skimmer basket before winterizing your pool for two main reasons. First, clearing out the basket ensures that no debris remains inside the skimmer that could rot or encourage mold growth during the winter months. Second, removing the basket allows you to install the winterizing plug or seal correctly at the bottom of the skimmer box.

After removal, clean the basket thoroughly and store it in a warm, dry location until spring. This prevents it from freezing and cracking due to moisture or exposure. Always ensure that after removing the basket and sealing the skimmer box, the system is properly winterized so no water remains in the skimmer throat or pipes. This helps maintain the structure and protects components during cold months.

Can I add winterizing chemicals to the pool before lowering the water level?

Yes, you should add winterizing chemicals to the pool before lowering the water level to ensure that the entire volume of water in your pool is properly balanced and protected. This includes algaecides, chlorine or non-chlorine shock, and sometimes a pool-grade antifreeze. Proper chemical levels at winterization will help prevent algae, bacteria, and staining during the colder months when the pool is not actively filtered.

It’s best to circulate the chemicals through the pool by turning on your filtration system for a few hours before draining the water. Once the chemicals are well distributed, lower the pool level below the skimmer and proceed with the winterizing steps for the equipment and plumbing. Skipping this step or draining too soon can result in uneven chemical distribution, which may lead to unsanitary water conditions and difficulties in spring startup.