When a swimming pool is filled in rather than fully excavated, the underground plumbing that connected the pool to its equipment pad stays in the ground. In most cases, this is not a long-term problem, old pool pipes are typically PVC or UPVC, which are stable underground and don’t degrade in ways that cause issues for buildings or services. However, there are specific situations where underground pipes from a pool fill-in do matter, and this guide covers all of them.
What Underground Pipework Does a Pool Have?
A standard in-ground pool has several runs of underground pipe:
Main hydraulic pipes:
- Suction lines: Run from the skimmer box (on the pool wall) to the pump. Typically 50-80mm diameter PVC.
- Main drain line: Runs from the main drain at the pool floor to the pump. Same diameter.
- Return lines: Run from the filter/equipment back to the pool return jets in the pool walls. Same diameter.
Speciality lines (where fitted):
- Pool cleaner (suction) line: Separate suction line for a pool cleaner attachment
- Water feature supply lines: For fountains, water blades, or spa jets
- Solar heating lines: PVC or PE pipe runs to roof solar collectors and back
- Pool heating lines: If a gas or heat pump heater is installed
Electrical conduits:
- Pool light conduit: Typically 20-25mm conduit running from the switchboard to the pool light niche
- Pump and equipment power conduits: Usually run in the same trench as hydraulic pipes
All of these run through the soil between the pool shell and the equipment pad, usually along the side of the pool, at depths of 300-600mm.
What Happens to These Pipes During Pool Removal?
The answer depends on which type of removal is being done.
Full Pool Removal (Full Excavation)
In a full pool removal, the pool shell and all surrounding soil is excavated. Pipe runs within the excavation zone are physically removed with the shell debris. The remaining pipe runs between the former excavation and the equipment pad are:
- Cut off at the excavation edge
- The cut ends are sealed (capped or filled with concrete)
- The remaining run in the soil is abandoned in place
After a full removal, the remaining pipe beyond the excavation edge is essentially inert, it’s a capped, empty PVC pipe buried at shallow depth. Unless a future excavation or building work intersects it, it causes no problems.
Partial Fill-In
In a partial pool fill-in, the pool shell stays in the ground. The plumbing through the shell (skimmer, main drain, returns, light niche) remains in place but is disconnected from the equipment at the surface. These pipes are typically:
- Plugged at the pool end: Rubber plugs or concrete grout are inserted into the fittings at the pool shell
- Cut and capped at the equipment end: Plumbing is disconnected at the pump/filter and capped
- Left in place underground between the two ends
The concern with partial fill-ins is that the pipes form a network of small voids through the fill zone, PVC pipes at 50-80mm diameter are not large structural voids, but they do mean the fill zone is not completely homogeneous solid material. Over decades, as the PVC degrades (a very slow process), these voids may eventually become true voids in the fill.
For most residential purposes, lawn, garden, paving, this is not a practical concern. For building a structure over the fill area, it is a consideration that should be disclosed to the structural engineer designing the footings.
Are Abandoned Pool Pipes a Problem?
For most situations, no. PVC pipes buried at 300-600mm depth, with ends capped, are stable for decades. They don’t corrode, don’t release harmful substances, and don’t create significant voids. The main scenarios where they become relevant:
Future excavation: Any future digging in the area, for a new pool, drainage works, footings, services, needs to know the pipes are there. Always locate underground services before excavating. See our guide on BYDA Dial Before You Dig and pool removal.
Building over the fill area: If you’re building a slab or footings over a partial fill-in, the structural engineer should know about the underground pipes in the fill zone. They may specify that pipes be grouted or removed from the footing zone.
Electrical conduits with live wiring: This is the only scenario where abandoned pool pipes are genuinely hazardous. If underground electrical conduit is left connected to the switchboard (i.e., the circuit was not properly isolated before removal), there is live wiring underground. This must not happen, electrical disconnection is a mandatory step before pool removal, and all pool circuits must be properly isolated and the wiring removed from live status.
A reputable contractor will ensure all electrical conduits are disconnected at the switchboard as part of the decommissioning process.
Solar Heating Pipes: A Special Case
Many Hunter region pools built from the 1990s onward have roof-mounted solar collectors connected by PE or PVC pipe runs that go from the equipment pad up through the roof space. These pipes typically run along the outside of the house or through internal walls.
When the pool is removed, solar heating pipes:
- Are disconnected from the pool plumbing at the equipment pad
- May be left in place in the roof or walls (if removal would require significant building work)
- Should have ends capped and drained to prevent trapped water
If you later want to remove the solar collectors from the roof (they become irrelevant once the pool is gone), engage a licensed plumber to drain and remove the pipework and a licensed roofer or builder to remove and patch the roof collectors.
The Main Drain: A Pool Safety Consideration
The main drain at the bottom of the pool floor is connected to the deepest point of the pool. In a partial fill-in, this fitting is in the filled section of the pool and is buried under fill material. It’s not accessible and not a concern once the pool is filled.
In a full removal, the main drain fitting and its pipe are excavated with the pool floor.
How to Locate Pool Pipes Before Future Work
If you’ve recently purchased a property where a pool was previously filled in or removed, and you need to know where the underground pipes are, options include:
- Ask the previous owners if they’re contactable, they may have plans or photos
- Check council DA records, pool installation may have been recorded with plans
- CCTV pipe inspection: A licensed plumber can run a CCTV camera through any accessible pipe end (at the equipment pad) to trace the route and condition
- Electromagnetic pipe locating: Specialist equipment can locate buried pipe runs
- Ground-penetrating radar (GPR): Can identify shallow buried features including pipe runs
For any project involving significant excavation near a former pool area, a GPR or pipe-locating survey before digging is worthwhile insurance.
Practical Recommendation
If you’re having a pool filled in and you plan future building works on the site, ask your contractor to:
- Record the location and depth of underground pipe runs before fill is placed
- Remove as much pipework as can be accessed within the excavation zone during the fill-in
- Provide a simple sketch of remaining pipe runs relative to site boundaries and the fill zone
- Confirm electrical conduits are properly terminated at the switchboard
This documentation becomes valuable if you ever need to build, excavate, or sell the property, and it costs your contractor minimal additional effort if requested upfront.
Underground Services and Dial Before You Dig
Pool plumbing is not registered with Dial Before You Dig (BYDA), it’s private infrastructure, not a public utility. So BYDA notifications won’t flag private pool pipes. This is why contractor knowledge and documentation of the pipe layout is important, public services records won’t cover it.
For other underground services in the excavation zone, council water mains, sewer, electricity, gas, and telecommunications, always obtain a BYDA reference before any excavation. See our full guide on BYDA and pool removal.
Frequently Asked Questions
Do underground pool pipes need to be removed when a pool is filled in? Not necessarily. Standard PVC pool pipes, properly capped, are stable underground for decades. Full removal is preferred when building over the area, but for lawn or garden use, capping and abandonment in place is generally acceptable.
Is there any risk of the underground pool pipes collapsing and causing subsidence? PVC pipes at 50-80mm diameter don’t create meaningful subsidence risk if they collapse over time, they’re too small to create a significant void. The risk is higher if the pipes are larger diameter or if there are multiple parallel runs in a concentrated area, but even then, the risk for a standard residential pool is low.
Should I tell buyers when I sell my property that pool pipes are underground? Yes, disclose material facts about the property. If you’ve had a pool removed or filled in and pipes remain underground, document this in your vendor disclosure. Most buyers and their conveyancers will accept this; what creates problems is discovering undisclosed underground infrastructure after settlement.
What if I find old pool pipes when digging in my garden? They’re almost certainly inert and non-hazardous. If the pipe appears to be a hydraulic (water) line, cap the ends. If it appears to be an electrical conduit, do not cut it until you’ve confirmed with a licensed electrician that it’s de-energised. Contact your pool removal contractor or a licensed plumber/electrician if you’re uncertain.
Can pool pipes be reused for other purposes (irrigation, drainage)? Potentially, if the pipes are in good condition and the routing suits another use, existing pool pipework can sometimes be repurposed for garden irrigation or drainage. A licensed plumber should assess the pipe condition and suitability before reuse.
Planning a pool fill-in and want to know what stays in the ground? Contact Hunter Pool Removals for a free site assessment and quote, covering Newcastle, Lake Macquarie, Maitland and the Hunter Valley.