Is It Too Hot to Drain Your Pool? Here are Some Options

Pools are often well worth the investment, as they make gatherings more enjoyable and hot days more bearable. Nonetheless, to keep them in good condition they must be maintained, and in some cases, drained. 

If you’re considering draining your pool during the summer, you’ve probably wondered, “When is it too hot to drain a pool?”

Continue reading to learn more about the answer, including why you should avoid fully draining your pool. We’ll also show you the proper techniques for partial draining, whether it’s an above-ground or in-ground pool. 

When Is It Too Hot to Drain a Pool?

In general, avoid draining your pool when the air temperature reaches 85°F or higher. Keep in mind that pools, regardless of material, are designed to function in an environment where they’re mostly filled with water. 

Exposing pool surfaces to extreme heat can cause damage, resulting in costly repairs. 

If you have a plaster pool, allowing bare surfaces to become dried out in hot temperatures can result in cracking very quickly.  Prolonged heat to bare vinyl surfaces can also cause it to become brittle.  

What’s more concerning is structural damage as a result of the hot weather’s drying effects. Sunny weather can rapidly dry out the bare pool surface on a hot day. 

We recommend draining your pool on days with moderate weather that are neither too hot nor too cold. Those would be in the spring or fall, but you’ll have to judge that based on your location.

If air temperature is above 85°F, but it’s a cloudy day there may be slightly less risk of damage as the surface won’t become dried out as quickly. Just ensure that water is back in the pool before the sun starts beating down on it again.

What Are the Dangers of Draining a Pool?

There are very few times when fully draining the pool is advised.  In most cases, it’s important to consult with pool professionals if you find that a full drain is truly needed.

If you find it’s absolutely necessary to perform a full drain of the pool, you must be aware of the do’s and don’ts for the type of pool you have. This is to avoid two major risks associated with emptying a pool which are:

1 – Pop-Ups

Pools are constructed to withstand the weight of the water pressing down on them.

When they’re drained, they lose the downforce that shields their structure from the pressure of the groundwater. Sometimes the pressure is so high that the pool pops out of the ground. 

Popping out is a risk that applies to nearly all types of in-ground pools if fully drained –vinyl, fiberglass, and gunite.

2 – Interior Deterioration

Since pools essentially hold water, their interiors are used to moisture. When the water is removed, the pool’s finishes might dry out, which will cause them to deteriorate and possibly develop cracks.

When Is It Necessary to Drain a Pool?

Given the significant risks with fully draining a pool, it’s best to only perform a partial draining when the need arises.  We’ll walk you through three scenarios in which draining a pool may be necessary

If you’re dealing with anything other than the situations listed below, you should probably first speak with a professional. They can then determine whether the problem necessitates draining or if there are other options. 

Restore Chemical Balance 

Maintaining a proper chemical balance in a pool is vital. Otherwise, the water itself can pose a negative impact on the pool’s structure as well as on anyone who swims in it. 

In some cases, you may be able to perform some quick fixes to restore the water balance, but sometimes diluting with fresh water may be the best approach.

Here are a few instances of chemical imbalance that are often best solved with a partial drain and refill.

High Cyanuric Acid (Stabilizer)

A high level of cyanuric acid (CYA), or stabilizer, will reduce your chlorine’s effectiveness, causing you to use more chlorine to keep the pool clean.  Although some products claim to reduce CYA levels, the most effective means is to perform a drain and refill.

High Total Dissolved Solids

A high level of TDS (total dissolved solids) can also be an indicator that your pool’s balance is a bit off.  

TDS is a measurement of the concentration of solids dissolved in water. They’re usually a combination of external elements that enter the water or additives that you use while cleaning, such as chlorine. 

The TDS normal range for a freshwater pool is 500-2,000 mg/L. When it exceeds this limit, it is important to check other measurements such as pH, free chlorine, metals (copper, iron), hardness and CYA.

High TDS may result in mineral stains on your pool’s walls, and the water may taste metallic.  

High Calcium Hardness

High levels of calcium hardness (CH) in the pool may cause cloudiness in the water or scaling around the surfaces of the pool. The ideal range for CH in a pool is 200 to 400 ppm. 

Although some treatments exist to reduce high CH, the most effective (and cheap) method is to perform a partial drain and refill using a water source that has lower CH.

Algae Swamp

In the unfortunate event that your pool has turned into a thick green swamp, it sometimes requires at least a partial drain and refill to get the water sparkling again.

While you can attempt to shock the pool with loads of chlorine to kill the algae, it is often a nightmare trying to remove the dead algae without constantly clogging the filter.  

Instead, you can use a combination of shocking the pool while also setting your filter to waste while vacuuming up the dead algae.  While vacuuming to waste, continue adding freshwater to the pool.

Major Repairs

It’s only natural that the pool may need repairs from time to time or during routine maintenance. After all, it has been operating for many years while enduring exposure to water pressure, chemicals, harsh weather, and various other factors. 

For example, the concrete floor may begin to crack, or the vinyl liner may tear and form multiple blisters. 

Just a quick reminder that not all cracks can result in leaks; in fact, they’re mostly superficial.  They simply occur as a result of the supporting structure contracting or expanding.  

On the other hand, structural cracks or vinyl tears may require draining the pool for repair, depending on the magnitude of damage.  Even superficial cracks may warrant repair as they can harbor algae growth making it more difficult to keep the pool clean.

Winterization

For pools in climates that are prone to freezing weather, it’s often recommended that in-ground pools are drained slightly below the return jets during the closing process. This partial draining allows you to blow out the lines and plug them without risk of water re-entering.

Just remember, before winterizing your pool you should wait until the water temperature is below 70°F. Otherwise, if you close the pool while the water is too warm, it may be more susceptible to algae growth in the off-season.

How Do You Drain a Pool?

The time it takes to drain a pool depends on its size, along with the method that you’re using to remove the water.  Some methods may take less than an hour, where others may take a full day.  

We’ll focus on one of the most common methods to drain a pool through use of a submersible pump.  However, know that there are several other ways to drain the pool even without this pump.

Before we get into the drainage steps, there are some general guidelines you should be aware of:

• Prepare to perform all necessary repairs so that you don’t have to drain the pool again
• Identify the drainage location in accordance with local regulations, such as a sewer outlet or the street
• Ensure your discharge location is far enough away from the pool that drained water won’t flow back underneath the pool structure
• If possible, avoid fully emptying in-ground pools as this can result in severe complications.  
• Try to keep at least 16 inches of water in the shallow end of the pool to avoid pop-out
• Acquire a submersible pump, which can be purchased or rented

How to Drain a Pool

1. Turn off the pool pump to avoid it running dry as water falls below the skimmer
2. Get a sturdy garden/backwash hose and connect it to the submersible pump
3. Position the other end of the hose to the discharge location 
4. Immerse the submersible pump in the pool
5. Connect the pump’s plug to a GFCI outlet
6. With the pump on, check the drainage area to ensure that there’s water coming out
7. Keep an eye on the drainage process and unplug the pump as soon as you’ve drained to the desired level

If you need to fully drain the pool, it’s strongly recommended that you consult with a pool professional in order to take any necessary steps in preventing the pool from popping out of the ground.

Hydrostatic Valves During Draining

If an in-ground pool needs to be fully drained, there are sometimes hydrostatic valves that must be opened in order to relieve pressure from excess water sitting below the pool.  A high water table below the pool can cause the entire structure to pop out of the ground without the counterpressure of water in a filled pool, in which these hydrostatic valves offset the risk.

There may be four to five hydrostatic plugs, but the number varies from one pool to another. They are often positioned at the deep end, mid-depth, and shallow end of the pool.

Quick Tip: Have replacement hydrostatic plugs on hand because they’ll likely be damaged during the process.

To fully drain a pool, a submersible pump is often the best solution. When the pump is no longer transferring water, you’ll need to replace the plugs as follows:

1. Depending on the type, you’ll need to either break a plaster layer or unscrew a plastic cover to get to the plugs
2. Remove the plugs with a hydrostatic removal tool by twisting counterclockwise
3. Detach all plugs, especially the deep-end plug, to release as much groundwater as possible
4. Allow for groundwater to emerge (a heavy flow is normal)
5. Replace the hydrostatic plugs before refilling the pool

Refill the Pool

Once you’ve finished all activities on the pool after draining it, you’ll want to get water back into it as soon as possible.

A typical garden hose connected to an outdoor spigot is a common means to refill the pool.  This process can take several hours or more, depending on how much water has been drained.  

Alternatively, having water delivered in a tanker truck is another means.  However, this is often more costly and requires some advanced planning.

Regardless of which method you use to refill the pool, it’s important to check the water balance afterwards.  There are many different types of test kits available to help you monitor the various attributes of your pool chemistry, including chlorine, pH, total alkalinity, and CYA.

What if it’s Too Hot to Drain?

Although partial draining is a common way to avoid the pool from popping out of the ground, it still may not be the best method in hot weather above 85°F.  Even partial draining can allow the surface of the pool’s structure to become dried out and damaged.

In an ideal world, it may be best to wait for cooler and cloudy weather. But, everyone knows that waiting for the perfect weather is not always practical, especially in urgent situations.

If you have a chemical imbalance in the pool that requires removal of old water, then it may be best to swap the water.  To perform a swap, follow these simple steps:

1. Set up a submersible pump in the shallow end (or stairs).  
2. Attach a hose to the submersible pump and place the other end at the proper discharge location.
3. Turn the pump on and measure the flow rate being discharged by timing how long it takes to fill a bucket.
4. Connect your fill hose to the spigot (or other water source) and measure the flow rate by timing how long it takes to fill the same bucket.
5. Adjust either the discharge or fill source so that their flow rates are similar.  This will ensure the pool’s water level stays constant during the swap.
6. Position the fill hose so that its end is at the bottom of the pool in the deep end.  
7. Turn on the fill water and the submersible pump at the same time.
8. Allow them to run long enough to provide the necessary swap of old water from the pool.

While this method may not provide a perfect means to fully swap 100% of the water in your pool, it will provide protection of your pool’s structure against sweltering temperatures with plenty of dilution.

Unfortunately, swapping water may not be a suitable choice if you’re looking to make physical repairs that require a dry surface. In that case, waiting for cooler temperatures is your best bet.

Final Takeaway

Now that you know when it’s too hot to drain a pool, you can choose an appropriate day based on the weather forecast.  

Alternatively, simply swapping the water can be an effective solution if you’re just trying to resolve chemical imbalance on a really hot day.

Ultimately, due to risks involved with draining the pool, it’s generally advised to only perform a partial drain unless it’s absolutely necessary for a full drain.  If performing a full drain, ensure you consult with a professional and take appropriate measures to avoid costly damage.  

Happy Draining (and Re-Filling)!