When a concrete pool is broken up, the rubble it produces, typically 40-80 tonnes for a standard family pool, doesn’t automatically have to leave the property. Crushed and screened to the right size, that same concrete can go straight back into the excavation as backfill, avoiding both the cartage cost of trucking it away and the cost of importing separate clean fill to replace it. Done properly, this is a genuine cost saving. Done carelessly, it’s also one of the more common ways a pool fill-in ends up failing a compaction test or, worse, breaching NSW waste rules.
Why Reusing Pool Concrete as Backfill Makes Sense
Every tonne of rubble that leaves a site attracts cartage and tipping or recycling fees, and every tonne of imported fill that replaces it attracts a supply and delivery cost on top. When the broken concrete from the pool itself is crushed on site or at a nearby facility and brought back as backfill, both of those costs shrink at once, on-site crushing avoids one leg of trucking each way, and using the site’s own material avoids buying in a full load of fresh road base or clean fill.
As an indicative guide only, using crushed pool concrete as backfill instead of full cartage-and-import typically saves several hundred to a few thousand dollars on a standard residential job, depending on pool size and how much of the rubble is suitable for reuse. The exact saving depends on the volume of usable material, the crushing method used, and how much supplementary fill is still needed to make up the void. Our pool excavation and backfill service prices this option against straight cartage and import so you can compare both approaches for your specific pool.
What “Crushed Concrete Backfill” Actually Means in Practice
Broken pool concrete isn’t backfill in its raw state. Rubble straight out of a demolished shell is an uneven mix of large chunks, twisted reinforcing steel and fine material, and dumping it into the hole as-is produces exactly the large voids and inconsistent density that fail compaction testing later. To become usable backfill, the material needs to go through a proper process:
- Steel separation. Reinforcing mesh and bar has to be cut free and pulled out, both because it’s valuable scrap and because leftover steel in the fill creates voids and corrosion risk underground.
- Crushing to a graded product. The concrete is crushed, either with a mobile on-site crusher for larger jobs or carted to a recycling facility, and screened to a consistent particle size, commonly a road-base-style grading such as DGB20 or similar, rather than left as random-sized rubble.
- Placement in controlled layers. Even good-quality crushed concrete has to go in the same way as any other fill, in layers of roughly 150-200mm, each compacted before the next is placed, not tipped in all at once.
When NSW Rules Allow It, and When They Don’t
Reusing crushed concrete on site is a genuine, common practice in the Hunter region, but it sits inside NSW’s resource recovery framework, not outside it. The relevant classifications are Virgin Excavated Natural Material (VENM) and Excavated Natural Material (ENM) for imported soils, and a separate resource recovery exemption or order pathway under the NSW Environment Protection Authority for recycled concrete products such as crushed concrete road base. Crushed concrete generated and reused entirely within the boundaries of the same residential property for the same job is generally treated more simply than concrete that’s trucked off site, processed, and brought back or sold on, which triggers the formal waste classification and resource recovery framework.
The condition that matters most for a pool job specifically is contamination. Concrete pool rubble must be assessed for asbestos before crushing or reuse, since older pool sites, pump sheds, coping and paving underlays built before 1990 sometimes contain asbestos-cement materials. Any confirmed asbestos-contaminated material cannot be crushed and reused as backfill under any circumstances; it must be removed by a licensed asbestos removalist and disposed of at a facility licensed to accept it. This assessment happens before crushing decisions are made, not after, and it’s a standard part of how a reputable contractor scopes a demolition and backfill job.
Does Crushed Concrete Compact as Well as Purpose-Made Fill?
Reasonably well, but not automatically. Crushed concrete with a good, consistent particle grading, plenty of fines mixed through the larger fragments, compacts to a solid, stable base, which is exactly why crushed concrete road base is a standard, accepted material for driveways and pavement subgrade across NSW. The risk is inconsistent crushing: rubble with too many large chunks and not enough fine material leaves air gaps between pieces that compaction alone can’t close, no matter how many passes a plate compactor or roller makes over it.
This is why compaction testing matters just as much, arguably more, on a crushed-concrete backfill as it does on imported fill. Our soil testing and compaction certification guide covers what that testing involves and the density standards (typically 95% Standard Maximum Dry Density, or 98% where a structure will be built) that apply regardless of what the fill material actually is. If you’re planning to build anything over the filled area, a geotechnical report is the document that confirms the fill, whatever it’s made of, is suitable for footings.
Working Out How Much You’ll Actually Need
Crushed concrete from the demolished shell rarely fills the entire void on its own. Breaking concrete increases its bulk volume (a phenomenon sometimes called “bulking”), but the crushing and screening process also removes a share of unusable oversize material and all of the reinforcing steel, so the net usable volume is typically less than the original pool’s excavated volume, not more. Expect to supplement with some imported fill to make up the difference, particularly in the top 300-500mm of the excavation, which is often better finished with clean, fine-graded material for lawn or garden establishment rather than crushed rubble right to the surface. Our pool fill volume guide walks through estimating the total cubic metres a given pool void actually needs, which is the starting point for working out how much of that volume the crushed concrete can realistically cover.
Occasionally the excavation also hits rock beneath the original pool footprint before backfill even starts, which changes both the dig and the total fill volume required; our rock excavation guide covers what that means for cost and timeline.
Crushed Concrete Pool Backfill: Frequently Asked Questions
Is it actually cheaper to crush and reuse concrete rather than truck it away?
Usually yes, on a standard job with reasonable machine access. The saving comes from avoiding one leg of cartage (out) and one leg of supply (import fill in), though the crushing process itself has a cost, so the net saving depends on pool size, access and how much of the rubble is genuinely suitable for reuse after asbestos assessment and steel separation.
Can I ask for my pool’s rubble to be crushed and put straight back in?
Yes, this is a normal request and many Hunter region contractors already default to it where the site and rubble condition allow. Confirm it explicitly when getting quotes, since not every contractor has mobile crushing equipment or includes it as standard.
Does crushed concrete backfill need the same compaction testing as imported fill?
Yes. The density standard and testing method (typically nuclear density gauge testing against a specified Standard or Modified Proctor density) apply to whatever material is placed in the hole. Crushed concrete isn’t exempt from testing just because it originated on the same site.
What if the pool rubble tests positive for asbestos?
It cannot be crushed or reused as backfill. Confirmed asbestos-contaminated material must be removed by a licensed asbestos removalist and taken to a facility licensed to accept it, handled entirely separately from the rest of the demolition and backfill scope.
Will crushed concrete backfill support a shed or garage built later?
Only if it’s been placed in proper compacted layers and tested to the standard your certifier requires, generally 98% MDD for structures. Get this specified and documented at the time of the fill-in rather than assuming it after the fact; retrofitting compaction certification on fill already placed years earlier is far more expensive than confirming it during the original job.
Talk to Us About Reusing Your Pool’s Concrete
Whether crushing and reusing your pool’s own rubble makes sense depends on the pool’s size, condition and what the finished ground needs to support. Get a free quote and we’ll give you an honest comparison between crushed-concrete backfill and standard cartage-and-import, priced for your actual pool.