How To Drain A Pool

Draining a swimming pool might seem as simple as placing a pump in the water and switching it on. However, removing thousands of litres of water from a pool needs to be carefully planned. If it is done incorrectly, you could damage the pool shell, flood your property or send chemically treated water somewhere it should not go.

At JKO Pool Construction, we generally recommend speaking with a pool professional before completely draining any swimming pool. This is particularly important for concrete pools, as groundwater pressure can cause serious structural problems when the pool is empty.

Below, we explain how to drain a pool safely, when draining may be necessary and why you should never empty your pool without first considering the risks.

Do You Need To Drain Your Pool?

Most routine pool maintenance can be completed without fully draining the pool. Modern filtration systems, pool vacuums and chemical treatments can resolve many common water-quality problems while the pool remains filled.

However, there are situations where some or all of the water may need to be removed.

You may need to drain your pool for:

• Major pool renovations
• Resurfacing or interior repairs
• Repairing cracks or structural damage
• Replacing tiles or coping
• Addressing extremely high chemical levels
• Removing excessive dissolved solids
• Treating severe staining or scaling
• Completing certain plumbing or equipment repairs
• Removing large amounts of contaminated water
• Preparing a pool for demolition or major alterations

If the issue only involves cloudy water, algae or slightly unbalanced chemicals, draining the entire pool should usually be treated as a last resort. A pool technician may be able to restore the water through filtration, cleaning and chemical adjustment.

Can You Drain A Pool Yourself?

It is physically possible to drain a pool yourself using a submersible pump, but that does not mean it is always safe to do so.

A swimming pool is designed to hold a large volume of water. The weight of that water helps counteract pressure from the surrounding soil and groundwater. Once the water is removed, the pool may become vulnerable to movement, cracking or lifting.

Before draining a pool, you need to understand:

• The type and condition of the pool
• Current groundwater levels
• Recent and forecast rainfall
• The location of any hydrostatic relief valves
• Where the water can legally and safely be discharged
• Whether the pool shell has existing cracks or damage
• How long the pool will remain empty

If you are not confident about any of these factors, contact a pool builder or technician before proceeding.

Why Draining A Pool Can Be Risky

The biggest risk associated with draining a pool is hydrostatic pressure. This occurs when groundwater beneath or around the pool pushes against the shell.

When the pool is full, the weight of the water inside it helps balance this external pressure. When the water is removed, the pressure below the pool may become stronger than the weight of the empty shell.

In severe cases, an empty pool can move, crack or lift out of the ground. This is sometimes referred to as a pool “popping” or “floating”.

The risk can be higher when:

• There has recently been heavy rain
• The property has poor drainage
• The pool is located in a low-lying area
• The surrounding soil holds water
• Groundwater levels are high
• The pool remains empty for an extended period
• The hydrostatic relief system is blocked or not operating properly

Here on the Gold Coast, heavy rain and periods of saturated ground are important considerations. Even if the weather is clear on the day you plan to drain the pool, water may still be sitting beneath the pool shell.

Can A Concrete Pool Be Drained?

Concrete pools can be drained, particularly when renovation, resurfacing or structural work is required. However, the timing and process need to be carefully managed.

Concrete pools are heavy, but they are not automatically protected from hydrostatic pressure. An empty concrete pool can still crack or move if there is enough groundwater beneath it.

Concrete pools may have hydrostatic relief valves installed in the floor. These valves are designed to allow groundwater to enter the pool rather than letting pressure build beneath the shell. Their presence does not mean that draining the pool is completely risk-free, however. The valves must be accessible and working correctly.

During our pool construction and renovation work, we plan the draining process around the condition of the pool, the required work and the local environment. The aim is to keep the pool empty only for as long as necessary and ensure any pressure around the shell is properly managed.

Can A Fibreglass Pool Be Drained?

Extra caution is required when draining a fibreglass pool.

Fibreglass pool shells are relatively lightweight compared with concrete pools. When the water is removed, pressure from groundwater or surrounding soil can cause the shell to lift, shift, bulge or deform.

The pool walls may also rely partly on the internal water pressure for support. Without that pressure, the walls can bow inwards or become damaged.

If you own a fibreglass pool, do not completely drain it without advice from the pool manufacturer or a suitably experienced pool professional. The cost of professional assistance is minor compared with the potential cost of repairing or replacing a damaged shell.

How To Drain A Pool Safely

The exact process will depend on the type of pool, the reason for draining it and the site conditions. The following steps provide a general overview, but professional advice should always take priority.

1. Confirm That Draining Is Necessary

Before removing the water, determine whether the problem can be solved another way.

For example, partially replacing the water may be enough to reduce high salt, calcium, stabiliser or dissolved solid levels. Pool chemicals and filtration may also be able to address algae or discolouration without a complete drain.

If renovation or structural work is required, the contractor completing the work should normally advise when and how the pool should be drained.

2. Check The Weather And Ground Conditions

Never drain a pool immediately before, during or soon after heavy rain.

Rainwater can soak into the ground and significantly increase hydrostatic pressure around the pool. Choose a period of settled, dry weather and check the forecast for the entire time the pool is expected to remain empty.

Remember that the ground can remain saturated well after the rain stops. If you are uncertain about the conditions beneath the pool, arrange a professional assessment.

3. Find An Approved Discharge Location

Pool water contains chlorine, salt and other chemicals, so it should not simply be pumped onto the street, into a stormwater drain or across a neighbouring property.

Local requirements can vary depending on where you live and what type of pool water is being discharged. Before starting, check the current requirements of your local council and water authority.

You may need to:

• Allow chlorine levels to reduce before discharge
• Adjust the pH to an acceptable level
• Use the property’s approved sewer connection
• Control the discharge rate
• Keep water away from stormwater drains
• Prevent erosion, flooding or damage to neighbouring properties

Do not assume that a suitable-looking drain is an approved discharge point.

4. Turn Off The Pool Equipment

Turn off the pool pump, filtration system, chlorinator, heater and any other equipment that should not operate while the water level is falling.

Pool pumps can be damaged if they run without enough water. Make sure automated schedules are disabled so the system does not switch itself back on while the pool is empty.

If you are unsure which equipment needs to be isolated, ask a pool technician or licensed electrician for help.

5. Use A Suitable Submersible Pump

A submersible pump is generally used to remove water from a swimming pool. The pump is placed in the deepest section of the pool and connected to a discharge hose.

The hose should reach the approved discharge location without sharp bends, leaks or sections that could move during pumping. Secure it where necessary and monitor the surrounding area throughout the process.

A larger pump may remove the water faster, but a higher discharge rate can overwhelm drains, cause erosion or create flooding. Faster is not always safer.

6. Monitor The Pool Continuously

Do not place the pump in the pool and leave the property.

Regularly check:

• The pool walls and floor
• The position of the pump
• The discharge hose and outlet
• The surrounding soil
• Nearby drains and low areas
• Changes in the weather
• Whether water is entering the pool from below

If you notice movement, cracking, bulging or groundwater entering the pool, stop and contact a professional.

7. Manage Hydrostatic Pressure

Hydrostatic relief valves may need to be inspected or opened when a concrete pool is drained. This should generally be handled by someone who understands the pool’s construction.

Incorrectly removing or damaging a valve can create additional repair work. It may also allow debris into the valve opening, preventing it from resealing properly.

If you do not know whether your pool has hydrostatic valves, do not guess. Speak with a pool builder before completely emptying it.

8. Complete The Work Promptly

Once the pool has been drained, complete the cleaning, repairs or renovations as efficiently as possible.

Leaving a pool empty unnecessarily increases the time it is exposed to groundwater pressure, weather and temperature changes. An empty pool can also be a fall hazard, so access to the area should be controlled.

Some pool finishes also should not be left dry for extended periods. Older finishes may crack, shrink or deteriorate after being exposed.

9. Refill The Pool Correctly

Before refilling, make sure all repairs have cured and any hydrostatic valves, plugs or fittings have been properly reinstated.

Once refilling begins, it is usually best to continue until the water reaches the required operating level. Stopping halfway for an extended period can create uneven pressure and may leave a visible mark on some new finishes.

Avoid switching the pool pump or filtration equipment back on until the water is at the appropriate level. Once filled, the water will need to be tested and balanced.

If the pool has received a new interior finish, follow the builder’s specific start-up instructions. New concrete pool interiors often require a carefully managed chemical-balancing and brushing process.

How Long Does It Take To Drain A Pool?

The time required depends on the pool’s volume, the pump’s capacity and the permitted discharge rate.

A smaller residential pool may take several hours, while a larger pool may take most of a day or longer. Restrictions at the discharge point can also slow the process.

The safest approach is not necessarily to use the fastest pump available. The water needs to be removed in a controlled way that does not flood the property, overload a sewer connection or cause damage downstream.

Should You Pressure-Wash An Empty Pool?

Pressure washing may be suitable for some concrete pool surfaces, but it is not appropriate for every finish.

Excessive pressure can damage paint, render, grout, tiles or an ageing interior surface. Acid washing is an even more specialised process and should generally be completed by an experienced professional. Incorrect use of acid can damage the pool finish and create serious safety risks.

Before cleaning an empty pool, identify the interior finish and choose a method that will not shorten its lifespan.

Can You Drain A Pool By Backwashing?

Backwashing removes a limited amount of water through the pool’s filtration system, but it is not generally the best way to completely drain a pool.

Allowing the water to fall below the skimmer level can cause the pump to draw air and lose its prime. Some systems have a waste setting or a dedicated main drain, but the configuration varies between pools.

Using a separate submersible pump is often a more controlled option. Check the pool equipment manufacturer’s instructions or speak with a technician before using the filtration system to lower the water significantly.

How Much Does Professional Pool Draining Cost?

The cost will depend on the size and type of pool, access to the property, the reason for draining and whether additional services are required.

The overall cost may include:

• Pump hire or professional pumping
• Water testing and treatment
• Cleaning
• Hydrostatic valve inspection
• Repairs or resurfacing
• Wastewater management
• Refilling and water balancing
• Restarting the filtration equipment

If you are already planning a pool renovation, draining and refilling will usually form part of the broader project planning.

Get Advice Before Draining Your Gold Coast Pool

Draining a swimming pool is not a routine maintenance job to approach without preparation. The combination of groundwater pressure, chemically treated water and a temporarily unsupported pool shell can create expensive problems if the process goes wrong.

At JKO Pool Construction, we build concrete pools across the Gold Coast. If your pool needs structural repairs, resurfacing or a larger transformation, we can assess its condition and plan the work carefully.

Before you empty your pool, contact our team to discuss what you are trying to achieve. We can help determine whether draining is necessary and advise on the safest approach for your pool and property.