Converting an old pool to a water tank or storage dam is a popular idea on rural Southern Highlands properties, and it is understandable, why remove something substantial when you can repurpose it? The honest answer is that it works in limited circumstances and fails in most. Structural reality, water quality rules and maintenance headaches make a purpose-built poly or concrete tank the better outcome for the vast majority of owners. If you are weighing up the options for your unused pool, our guide to what to do with an unused pool covers the full range of alternatives alongside removal.
The idea’s appeal on rural properties
Many Highlands rural properties rely on tank water or dam water for household supply, stock, fire-fighting and irrigation. An existing pool is a large, watertight structure that is already in the ground. The appeal of converting it to water storage rather than paying for removal makes intuitive sense, particularly for owners on large lifestyle blocks around Moss Vale or Robertson.
The pool holds 50,000 to 120,000 litres in many cases. A comparable polyethylene rain tank holds 10,000 to 22,500 litres. The pool represents a volume of storage that would cost $2,000 to $5,000 or more to replicate with new tanks. On paper, converting it rather than removing it saves both the removal cost and the new tank cost.
The question is whether the conversion actually works in practice.
Structural reality: pools are not tanks
The fundamental problem is that pools are designed to contain water under normal operating conditions, with a specific water level maintained at all times. They are not designed for:
- Repeated empty/full cycles: Pools drained and left empty frequently develop cracking. Concrete pools in particular suffer from ground pressure (hydrostatic pressure from the surrounding soil) when there is no water inside to counteract it. A pool left empty long-term can buckle or crack for this reason.
- Variable water level: A farm storage tank goes from full to nearly empty over a dry summer. A pool cycled through those fill variations experiences far more stress than it was designed for.
- Roof collection: A pool has no roof. An uncovered open water surface in the Highlands collects leaves, bird droppings, insects, algae and roof runoff from surrounding vegetation. Keeping open water hygienic for any use requires ongoing treatment that a proper tank avoids.
| Feature | Swimming pool | Purpose-built poly tank | Dam |
|---|---|---|---|
| Designed for variable fill levels | No | Yes | Yes |
| Covered from contamination | No | Yes | No |
| Ground pressure rated when empty | No | Yes | N/A |
| Suitable for potable supply | No | Yes (with filtration) | No |
| Maintenance cost over 10 years | High | Low | Moderate |
| NSW WaterNSW notification required | No | No | Often yes |
NSW water quality and use restrictions
Even setting aside structural issues, NSW rules on water quality for different uses matter.
NSW Health, private drinking water supplies sets out requirements for private water supplies used for drinking and cooking. A pool-converted storage system open to the elements, with chlorinated surfaces and no filtration, will not meet these requirements without significant treatment infrastructure. Using the converted pool for household drinking water is not a viable outcome.
For stock water and irrigation, the requirements are less strict, but contamination risks from open storage and pool surface chemicals remain. Chlorine residues break down over time but algae and bacterial contamination in open water is a persistent issue without regular treatment.
NSW WaterNSW, dams and water storage governs water licences for dams and surface water collection in NSW. Converting a pool to a collection dam in a catchment subject to licensing requirements triggers notification and potentially licensing obligations.
Dam conversion, even harder
Converting a pool to an actual dam, a structure that collects and stores surface water runoff, faces additional regulatory and practical constraints.
First, a dam in NSW requires a Water Access Licence if it collects more than a minimal amount of water, depending on the catchment and water sharing plan in place. The Wingecarribee River catchment is a protected water supply catchment, which imposes stricter controls.
Second, a pool structure is designed for internal water pressure, not the dynamic loads and seepage pressures of a dam. Pool walls and floors are not engineered to resist external soil loads from water-saturated ground on all sides, which is the situation a dam experiences. A pool converted to an earth-surrounded dam would require structural assessment and likely reinforcement.
Third, a pool in a garden setting is not typically located where runoff naturally concentrates. Catchment efficiency, the volume of runoff a dam collects relative to its capacity, would be very low for a pool sitting in a backyard, not in a natural waterway.
When it might work (stock water, irrigation)
There is a narrow but genuine case for pool conversion on rural properties: non-potable stock water or irrigation storage where:
- The pool is structurally sound and has been maintained with water in it
- It will be refilled from an existing bore, tank or pump, not from open catchment
- Water quality for the intended use (stock or irrigation) is adequate with basic treatment
- The pool is in a location convenient to the area being irrigated or where stock drink
In this scenario, adding a shade sail or shade cloth to limit algae growth, fitting a filter to the delivery line, and maintaining basic water treatment gives a functioning stock or irrigation tank at lower cost than full removal and new tank installation.
This is a minority of cases. For most owners, the maintenance burden of keeping an open pool structure clean and structurally sound for secondary water use outweighs the savings.
The more common answer: remove and install a proper tank
The most common outcome for rural Highlands owners who seriously investigate pool conversion is to proceed with full removal and install a purpose-built poly or concrete tank instead. The reasons:
- A 22,500 litre poly tank costs approximately $1,500 to $3,500 fully installed, can be positioned where catchment is best, and requires minimal maintenance
- The full pool removal clears the space for garden, shed, orchard or other use
- A proper tank with a first-flush diverter and covered storage provides genuinely clean water
Our full pool removal service includes the complete excavation, backfill and reinstatement. The freed space can be used for a productive orchard or garden, see our guide to converting a pool site to a garden or orchard for what is possible.
If the cost of full removal is a constraint, a partial pool removal fill-in is a lower-cost alternative that decommissions the pool without full excavation.
Case study alternatives
The following examples are indicative composites, not actual projects, offered to illustrate typical outcomes.
Rural property near Moss Vale: 75,000 litre inground concrete pool. Owner investigated conversion to stock water. Structural assessment found base cracking from previous dry period. Full removal and 2x 22,500 litre poly tanks installed at the existing tank stand location. Net water storage similar, maintenance far lower.
Robertson lifestyle block: 55,000 litre fibreglass pool. Owner wanted irrigation storage for orchard. Shell structurally sound. Added shade cloth frame, connected bore pump, fitted sediment filter. Used for irrigation for two seasons. Ongoing algae management and one liner repair eventually prompted owner to remove and replace with dedicated irrigation dam, noting the pool removal on clay soils considerations were a further complication.
Both outcomes, removal and conversion attempts, demonstrate the core point: conversion works temporarily at best, and full removal with purpose-built storage is the more reliable long-term answer.
FAQs
Can I legally use my old pool as a rainwater tank?
In principle yes, for non-potable uses such as stock and irrigation on rural lots. For potable drinking water, NSW Health requires compliance with drinking water quality standards that open pool-based storage cannot easily meet. You should check with Wingecarribee Council if any development approval is needed to change the use of the structure.
Does converting a pool to a dam need a water licence?
It depends on what you are collecting and where. Surface water collection that exceeds minimal volumes in catchments under a NSW Water Sharing Plan requires a Water Access Licence. The Wingecarribee River catchment has protected catchment status. Bore water or on-property tank fill does not trigger licensing in the same way. Contact WaterNSW for your specific property.
What is the main structural risk of converting a pool to water storage?
The main risk is that pools are not designed for variable fill levels over long periods. A pool cycled between full and nearly empty loses structural integrity faster than one maintained at a constant operating level. Hydrostatic pressure from surrounding soil when the pool is nearly empty can cause cracking or wall movement, particularly in concrete shells.
Is a fibreglass pool better suited to conversion than a concrete pool?
Fibreglass is more flexible and can tolerate fill-level variation somewhat better than concrete, but it still has the contamination and open-storage issues. Neither pool type is a genuinely adequate substitute for a purpose-built covered tank for potable water supply.
What’s the cost comparison between conversion and removal plus new tank?
A conversion involves minimal cost if the pool is structurally sound (shade cloth, filter, treatment). Full removal plus a 22,500 litre poly tank costs approximately $8,000 to $18,000 depending on the removal scope and tank specification. If the pool is already cracked or deteriorating, removal and replacement is clearly preferable.