Sizing for farm scenarios
- Main farmhouse (4–6 people): 2500L three-chamber
- Smaller farmhouse or couple (2–4 people): 1500L
- Workers' quarters / shearers' quarters: Dedicated 1500L
- Guest cottage / B&B: Dedicated 1500L
- Multiple dwellings: One tank per dwelling — simpler for council and pump-out
Why farms choose poly
Farm access is the deciding factor. A HIAB truck delivering a 1,500 kg concrete tank needs a wide, level approach with no overhead branches. Farm tracks rarely meet that brief. A ute carrying a 61 kg poly tank goes anywhere a 4WD can go. We've delivered tanks across stock crossings, down farm dams' edges and into remote paddocks where a concrete delivery would have been physically impossible.
Poly's other farm advantage is chemical resistance. Farm bores often carry mineralised water; some areas have high-sulphate soils. Concrete suffers in both. Poly is inert and unaffected.
Vehicle traffic considerations
Once buried with 300–600mm of cover, a poly septic tank handles light vehicle traffic — cars and utes — without issue. Heavy machinery (tractors, harvesters, trucks) should never drive directly over the tank or absorption trench regardless of material. Route farm vehicle paths around the system, mark the trench area, and educate anyone operating machinery on the property.
Frequently asked questions
What size septic tank does a farmhouse need?
A standard farmhouse with 4–6 occupants typically needs a 2500L three-chamber tank. Smaller farmhouses with 2–4 people are well-served by a 1500L. Workers' quarters and shearers' sheds usually get their own dedicated 1500L tank because their occupancy is intermittent.
Can one septic tank serve multiple farm buildings?
Yes, if the buildings are close together and a single trench can carry the inlet load. In practice, most farms use one tank per dwelling — the main house gets a 2500L, the worker's cottage or guest cabin gets its own 1500L. This simplifies pump-out scheduling and council approvals.
Are poly tanks strong enough for farm use?
Yes. Certified poly septic tanks handle normal vehicle traffic over the buried tank (cars, light utes). Tractors, trucks and heavy machinery should not drive directly over the tank or the absorption trench regardless of tank material — that's a routing question, not a tank-material question.