How Long Can You Leave Your Pool Empty?


Man in green outfit cleaning an above ground swimming pool that has been drained.

It can be straightforward maintaining a swimming pool while in use over the summer. However, once the season is over and it is too cold to go for a swim, how are you supposed to take care of it then? The winter can be hard on a pool; between the collection of falling leaves and dirt and freezing conditions, many pool owners opt to drain the pool to make maintenance easier once it is time to swim again. But does this really help?

How long can you leave a pool empty? It is not advised to leave a pool empty for extended periods: Depending on the level of the water shelf, sustained pressure on an in-ground pool without water can cause external damage. Additionally, a drained above-ground pool can receive structural damage from the elements.

In other words, if you are planning to empty your pool for the winter season or maintenance, it is best to only do so for a limited amount of time to avoid long-term damage. The remainder of this article will discuss the proper measures you must take when it comes to draining pools and ensuring longevity.

How Long Can a Pool Stay Empty?

The overall consensus for any type of pool is to leave it drained for the least amount of time possible. Knowing the construction of your pool will give you a better idea of how long you can leave it drained; some can be left empty for more extended periods, while other pools cannot be left drained for more than 15 minutes.

Types of In-Ground Pools

Empty in ground swimming pool ready for replacement of old vinyl lining or liner

There are three types of in-ground pools; each is made with different foundations:

Concrete Pools

Concrete pools are the most common type of pool. They are entirely customizable and offer robust construction. They are also the most expensive.

Because they are constructed with the most durability, they are the least likely to experience catastrophic damage when left empty. Still, it is highly advised not to leave a pool empty for extended periods. Direct sun and other environmental effects can cause harmful erosion or cracks to the interior surface of a concrete pool.

Vinyl Lined Pools

Vinyl lined pools are the second most popular pool material and rising because of the low initial cost. They are constructed using wall plates (vinyl, plastic, or steel).

Vinyl lined pools are not made to withstand being emptied. Fortunately, repairing small damages can be done with equipment designed to be used underwater. If it is absolutely necessary to drain a vinyl pool, contact a professional because specialized bracing will be needed to keep the pool intact.

Fiberglass Pools

Fiberglass pools are the third type of in-ground pool. Manufactured off-site, a hole is created in the shape of the shell and lined with a material that adheres the mold to the soil. The pool is filled with water, and as it fills, a material is backfilled into the spaces between the foundation and the shell.

Fiberglass pools should not be emptied; they run the highest risk of experiencing severe damage. The shell of the pool is designed to be filled with water; they are not intended to withstand the pressure of the surrounding earth. If it is necessary to drain a fiberglass pool, consult a professional; similarly to vinyl pools, the fiberglass shells need to be braced and fixed with specific materials.

Above-Ground Pools

Of course, another type of pool worth mentioning are above-ground pools. These pools are usually purchased online or through a box store and can be manually set up by the user. As you begin to fill the pool with water, its sides begin to take form, and metal poles are used to frame its final shape.

Above-ground pools should not be emptied unless you plan on taking down the entire unit and storing it away for the winter. However, if you do this, you must make sure the material on the pool is completely dry and it is stored in a climate-controlled space. This will help you avoid mold or mildew from developing while not in use.

Alternatively, if you do leave water in the pool—as is often the case with above-ground pools housed within a deck—make sure you cover it and have a method of removing excess water from the top in case it rains. You should also unplug any electrical equipment running, such as a pump.

For more information about winterizing above-ground pools, check out this article.

What Can Happen to a Pool If Left Empty?

Many pools are built to withstand a lot, but it can still experience the following types of damage if it’s left empty for too long:

  • Cracks
  • Leaks
  • Foundation damage
  • Damage to the pool’s accessories (lights, heating, and pumps)
  • Damage to the surrounding area

Another form of damage that pools can experience is float, which is what happens when water begins to fill the space between the shell of the pool and the ground underneath. Although float is a rare occurrence, it is possible with enough neglect.

Repairs for these types of damages are costly and time-consuming. For that reason, it is best to consult a professional when tending to pool maintenance outside of routine cleaning, especially when it involves draining your pool.

Of course, the level of damage you can see will depend on a number of factors as well:

  • The water shelf
  • The weight of the surrounding structures
  • The location of your pool
  • The pool’s material
  • How Can I Leave My Pool Empty?

If you have to drain your pool, know that extended exposure to the elements (besides water) can eventually lead to erosion or an unbalanced pressure build-up on the sides of the pool from the earth surrounding it. This can further lead to cracking, leaking, and other types of structural damage.

However, there are ways that you can ensure your pool stays protected while it is drained. For one, you can take advantage of an in-ground pool’s hypostatic pressure release valves that have been built into the foundation. Simply break the plaster lining to open the valves; this will allow water from the water shelf to drain into your pool, releasing some of the pressure on its foundation.

You will also need a drainage pump attached to a hose to discharge any water build-up (often the case with above-ground pools). Make sure the hose leads to a storm drain or an area with a slope going downhill and away from your pool. This is so that groundwater does not gather near the pool and cause foundation damage from the outside; this is especially the case with pools that are in a valley or small dip in the earth.

How Do I Maintain a Pool without Draining it?

In-ground pools require the most attention and care out of all the pool varieties, especially concrete pools. Concrete is porous, which makes a great home for algae: the biggest enemy you will be facing. If your pool is really odorous and dirty, draining and cleaning may be your only option.

Still, unless there are specific damages that need to be repaired, a vigilant cleaning regiment will have any type of pool beautified and ready to refill in very little time, reducing the need to keep it drained for too long.

In many cases, it is not even necessary to drain your pool. Consistent care and proper maintenance will keep your pool clean and beautiful. And, if push comes to shove, you can always hire a cleaning company to handle the brunt of the workload.

Alternatively, if you want to save the expense and get your hands dirty, the recipe is simple to keep a pool clean and sanitary:

  • Skimming
  • Backwashing
  • Vacuuming
  • Monitoring chemical levels

Conclusion

Although it may be tempting to drain your pool at the end of the swimming season to make cleaning and maintenance easier, doing so is more likely to cause more harm than help.

In-ground pools are very strong and can endure a lot, but if you leave them empty for long, the outside pressure of the earth around it can eventually lead to leaks and cracks in the pool’s sides and even foundation.

Any dirt or debris that falls into an in-ground or above-ground pool can begin to erode the surface, allowing water to start seeping into the ground around it and begin to cause more structural damage.

The best way to avoid all of this is to consult a local pool professional or cleaner to help with the maintenance of your pool or continue to care for it on your own with regular skimming, backwashing, vacuuming, and chemical/pH balancing.

However, if you absolutely have to empty your pool, make sure you only do it for a short period; doing so will save you time and money otherwise spent repairing long-term damage.

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