Absorption Trenches & Effluent Irrigation

BluenGrey specalises in wastewater plumbing for absorption trenches, evapotranspiration beds and effluent irrigation.

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Need advice?

If you have a system with effluent irrigation or absorption trenches that are failing or in need of improvement, but you're not sure where to start, we can help you.

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New to septic?

If you have not had an onsite wastewater treatment system and you need absorption trenches or effluent irrigation installed or upgraded, we can take care of this for you.

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Somewhere in between?

Regardless of how much or how little you know, we can help ensure your wastewater is managed safely and efficiently on your property.

Why do I need a wastewater disposal area?

If you have an aerated wastewater treatment system (AWTS) or a septic tank, the wastewater will need to be disposed of onto a designated area of your property.

This area is often called a 'disposal area' and it is usually specified in the Geotechnical Report for your property. If you don't have a Geotechnical Report, also known as an On Site Wastewater Management Report, get in touch with us and we can help you arrange one. 

Learn more about Geotechnical Reports in our New Systems FAQ.

Absorption Trench for wastewater

What are the types of effluent disposal methods?

There are several options for how wastewater is irrigated or disposed of on your property; which is most suitable will be based on your Geotechnical Report. If your effluent irrigation or absorption trenches are failing or need to be improved or installed, we can help. With our experience in wastewater, we can ensure that your wastewater is managed safely and efficiently on your property.

Absorption trenches for wastewater

Absorption trenches

A shallow, underground trench that can vary in design, width and length depending on the type of soil and the size of your house. Wastewater flows downhill from the septic tank to the trench. A collection well with a pump can be installed if the trench location is higher than the septic tank.

  • Common disposal method for septic tanks and AWTSs.
  • Sites with limited space available for effluent disposal.
  • Good for free draining sub soils.

Typical absorption trenches are 600mm or 1200mm wide and up to 15m in length.

BluenGrey Evapotranspiration Wastewater Beds in NSW

Evapotranspiration beds

Used when soil conditions are less suitable for absorption trenches and there is limited space. Typically, they are a rectangle area of ground that is excavated up to 600mm deep, filled with gravel and plumbed to disperse the water evenly. The top soil is moulded over the top of the bed and planted with grass and other plants.

  • Common disposal method for septic tanks and AWTSs.
  • Sites that prevent use of irrigation due to lack of space.
  • Sites that prevent the use of absorption trenches due to clay soils.
  • Good for small sites.

Typically they are a rectangle area no more than 4m wide and 20m long of ground that is excavated, filled with gravel and plumbed to disperse the water evenly. The top soil is moulded over the top of the bed and grass and other plants are used to encourage vegetation growth in this area.

BluenGrey Sub-surface Wastewater Irrigation System in NSW

Sub surface effluent irrigation

Effluent grade poly pipe buried underground, with evenly spaced drip emitters which allow a pre determined amount of wastewater into the soil across a wide area.

  • Common disposal method for AWTSs.
  • Property owners wanting the wastewater underground so that they do not have to see it or have exposure or contact with wastewater.
  • Soil types that benefit from shallow irrigation and steep blocks.
  • No damage to sprinklers or mowers, vehicles, tractors or animals.
Surface spray irrigation in South East NSW

Surface spray irrigation

Surface spray irrigation can be simply a line of above ground purple pipe and sprays.

  • Common disposal method for AWTSs.
  • Sites that have ground slope less than 20 degrees.
  • Properties that have rocky ground (unable to bury poly pipe underground).
  • Properties that have a larger area for above ground surface sprays.
  • Soil types that benefit from surface spray.
BluenGrey's guide to septic systems

Resources & FAQ

Useful guides and Council information, and answers to the most common questions we get asked about AWTS and septic tank systems.

Need a specialist in wastewater plumbing for your absorption trenches, evapotranspiration beds or effluent irrigation?

Get in touch with our friendly and knowledgeable team to organise an on-site inspection today.

BluenGrey Wastewater Irrigation Service Provider in South East NSW


  • "Super professional and experienced"

    “Rod Wilks and the crew at BluenGrey put in a massive water tank for us after our old concrete tank began to leak. We were caught north of the Qld border the whole time but just a phone call was all that was needed for Rod and the team to take care of everything for us during our absence, including design, liaison with manufacturers, site preparation and integrating the new tank with existing lines. We genuinely recommend this business to anyone who wants a super professional and experienced outfit for everything tanks and septics.”

    – Bernie and Deb Morrison, Kianga.

  • "I can’t recommend BluenGrey highly enough"

    “BluenGrey are an absolute pleasure to deal with. Their Service Technicians are always professional and reliable, and I like to know that our wastewater system is looked after so we’re always meeting our Council’s regulations. I feel reassured knowing I can call on them should I have any worries about our system, and especially that they can respond to emergencies.”

    – Emma, Shoalhaven

  • "BluenGrey are a great ‘one stop shop’ service at competitive prices"

    “Having made the decision to move to a semi-rural property at Yass we investigated options for our grey and rain water requirements. We approached BluenGrey who provided a range of options for us to select from. Their personal and professional approach, which included on-site meetings, ultimately led us to choose to proceed with BluenGrey who offered a ‘one stop shop’ service at competitive prices. The installation was trouble free and their follow-on service and advice has been excellent. We are completely satisfied with the BluenGrey services and have no hesitation in recommending them to future customers.”

    – Col and Anne Eade

  • "Rod’s expertise is exceptional"

    “We would like to thank Rod for all his guidance and patience while we were investigating water and sewerage systems, and asking a myriad of questions. We had never built before and knew nothing about what we needed for water and sewerage, so Rod was a fountain of knowledge. His expertise has been exceptional. Both the water tank and the sewerage system were installed hassle-free and passed Council inspection without any issues. We look forward to an ongoing relationship with Rod when he visits to do the necessary checks and balances of our sewerage system”

    – Melissa and Scott Jobson, Tapitallee

  • "BluenGrey were very helpful in every respect"

    “From our initial conversations through to final installation BluenGrey were very helpful in every respect, and courteous and obliging with regards to my requirements. Work commenced on time as planned with pictures texted through to us during the installation showing progress. All in all job a well done with zero issues. I would recommend BluenGrey to anyone considering waste disposal units and / or rainwater tanks.”

    – Steven Hawke, Longbeach