When installing a septic system, one of the most critical factors is ensuring that the soakaway (drainage field) is placed at a safe and effective distance from the septic tank.
Placing the soakaway too close to the septic tank can lead to:
❌ System failure – Wastewater may not be properly filtered, leading to pollution.
❌ Groundwater contamination – Harmful bacteria and nitrates can seep into drinking water sources.
❌ Sewage backups – If the soakaway is not placed correctly, wastewater can flood the area or back up into the tank.
❌ Legal violations – Many countries have strict minimum distance regulations for septic systems.
So, how far should the soakaway be from the septic tank? The recommended minimum distance is typically 5 to 10 meters (16 to 33 feet), but this varies depending on local regulations and soil conditions.
Let’s break down everything you need to know.
What Is a Septic Tank Soakaway?
A septic tank soakaway, also called a drainage field, is an underground system that disperses treated wastewater from the septic tank into the soil. The soakaway allows bacteria in the soil to further break down organic matter, preventing pollution.
A soakaway system typically consists of:
✔️ Perforated pipes laid in trenches filled with gravel or stones.
✔️ A filtration area where wastewater is absorbed into the ground.
✔️ Soil layers that naturally filter harmful bacteria and nutrients.
A soakaway is not the same as a soakaway crate system, which is only suitable for rainwater and cannot legally handle septic effluent.
Recommended Distance Between a Septic Tank and a Soakaway
1. General Distance Guidelines
| Type of System | Recommended Distance from Septic Tank | Additional Considerations |
|---|---|---|
| Drainage Field (Perforated Pipes in Trenches) | 5-10 meters (16-33 feet) | Must pass a percolation test to ensure proper drainage. |
| Seepage Pit or Soakaway Pit (Less common) | 10-15 meters (33-50 feet) | Risk of clogging and groundwater pollution if poorly designed. |
| Septic Tank to a Water Well | At least 15-50 meters (50-164 feet) | Prevents contamination of drinking water. |
| Septic Tank to a Property Boundary | At least 2-5 meters (6-16 feet) | Required to prevent property disputes and flooding. |
📌 In most cases, a soakaway (drainage field) should be at least 5 meters away from the septic tank to allow proper filtration and prevent groundwater contamination.
2. Country-Specific Regulations
Septic system regulations vary by country and region. Below are some common requirements:
✅ United Kingdom (Building Regulations Part H & Environment Agency Rules)
- The soakaway (drainage field) must be at least 10 meters from a watercourse.
- The septic tank must be at least 7 meters from a habitable building.
- The soakaway must be at least 15 meters from a water supply (well or borehole).
✅ United States (EPA & Local State Regulations)
- Septic tanks must be at least 10-25 feet from houses (varies by state).
- Drainage fields must be at least 50 feet from wells to prevent contamination.
- Many states require soil percolation tests before installing a soakaway.
✅ Australia & Canada
- Minimum distance of 5-10 meters between septic tanks and soakaways.
- 15+ meters required between septic soakaways and water sources.
📌 Always check local building codes before installing a septic soakaway to ensure compliance.
Why Does Distance Between a Septic Tank and Soakaway Matter?
Placing the soakaway too close to the septic tank can cause serious issues, including:
❌ 1. Risk of System Overload
- If the soakaway is too close, it may become overloaded with wastewater before it has time to naturally drain and filter through the soil.
- This can cause sewage pooling on the surface or slow drainage.
❌ 2. Groundwater Contamination
- Septic effluent contains bacteria, nitrates, and organic matter.
- If a soakaway is placed too close to the tank, untreated wastewater may contaminate nearby wells or groundwater sources.
❌ 3. Structural Damage & Land Instability
- Excess water near the septic tank can weaken the soil, leading to sinkholes, shifting ground, or cracks in foundations.
❌ 4. System Failure & Costly Repairs
- A poorly placed soakaway can become clogged with sludge and fats, leading to system failure.
- Fixing a failed soakaway often requires digging up and replacing the entire drainage field, which can be expensive.
How to Properly Install a Septic Tank Soakaway
✅ 1. Perform a Percolation Test
A percolation test (P-Test) measures how well the soil absorbs water.
- If the soil drains too fast, contaminants can reach groundwater.
- If the soil drains too slowly, the soakaway can flood or clog.
✅ 2. Follow Legal Distance Requirements
- Place the soakaway at least 5-10 meters from the septic tank.
- Keep it at least 15 meters away from wells or drinking water sources.
- Ensure proper separation from buildings, trees, and property boundaries.
✅ 3. Use the Correct Soakaway Type
- Drainage Field (Best Option) – A system of perforated pipes that allows wastewater to slowly filter into the soil.
- Soakaway Pit (Riskier Option) – A deep hole filled with gravel, but prone to clogging.
- Reed Bed System (Eco-Friendly Alternative) – Uses plants to filter wastewater naturally before it enters the ground.
✅ 4. Ensure Proper Maintenance
- Pump out the septic tank regularly (every 3-5 years).
- Avoid flushing grease, wipes, or harsh chemicals that can clog the soakaway.
- Monitor the soakaway area for pooling water, bad odors, or slow drainage—these can be signs of failure.
Common Mistakes to Avoid
🚨 Placing the soakaway too close to the septic tank – Causes rapid saturation and system failure.
🚨 Ignoring soil conditions – Poor drainage leads to flooding or groundwater contamination.
🚨 Using a soakaway crate system – These are only designed for rainwater and are illegal for septic effluent.
🚨 Neglecting maintenance – A clogged system can cost thousands to fix.
Final Answer: Recommended Distance Between Septic Tank and Soakaway
✅ At least 5-10 meters (16-33 feet) from the septic tank for a standard drainage field.
✅ At least 15 meters (50 feet) from wells or drinking water sources.
✅ At least 10 meters (33 feet) from watercourses like rivers or streams.
💡 Always follow local regulations and conduct a percolation test before installing a soakaway. Proper placement ensures long-term efficiency and prevents costly repairs!