Home Drainer Interview questions
Drainer interview questions
The questions people actually get asked for this role, and what each one is really testing.
What to expect
Interviews for drainer roles typically assess your technical knowledge, safety awareness, and ability to work as part of a team. You'll need to show you can read plans, install pipes to correct falls, and test systems for compliance.
- Technical: Questions about pipe laying, grades, materials, and tools like lasers and CCTV cameras.
- Safety: Questions about trenching, confined spaces, and working around heavy machinery.
- Process: Questions about how you approach a job from start to finish.
- Behavioural: Questions asking for examples of how you've handled problems or worked in a team.
- Scenario: Hypothetical situations that test your judgement under pressure.
- Compliance: Questions about Australian standards and regulations.
The interview process usually starts with a phone or video screen, then a face-to-face interview with a supervisor or project manager. Some employers include a practical assessment or a site walkthrough. You might be asked to demonstrate your knowledge of plans or tools.
- 1
Can you walk me through how you set out and install a drainage run from plan to completion?
Why they ask: This tests your ability to follow a process, read plans, and apply technical skills in sequence.
How to structure your answer: Walk-through: start with reading plans, then mark out, excavate, prepare bedding, lay and join pipes, install inspection points, and test. Finish with site clean-up and compliance sign-off.
Example answer
“First, I review the drainage plans and specifications, checking pipe sizes, material types, and fall requirements. I mark out the run on site using a laser level or string line, making sure I account for any existing services. Then I excavate the trench to the right depth and prepare the bedding, usually with crushed rock or sand. I lay the pipes, starting from the downstream end, and join them using the appropriate method for the material, such as solvent cement for PVC or rubber rings for concrete. I check the grade with a pipe laser as I go. Once the run is complete, I install inspection points and connect to the mains. Finally, I test the system for leaks using water or air pressure, and I ensure everything meets AS/NZS 3500 and local water authority requirements before backfilling.”
- 2
Tell me about a time you had to deal with a drainage problem on site, such as a blocked or leaking pipe. How did you resolve it?
Why they ask: This assesses your problem-solving skills and ability to work under pressure.
How to structure your answer: STAR: Situation, Task, Action, Result. Describe the problem, your responsibility, the steps you took, and the outcome.
Example answer
“On a residential subdivision, we had a section of sewer line that failed a leak test. I was asked to find the cause. I used a CCTV drain camera to inspect the line and found a joint that hadn't sealed properly. I cut out the faulty section, re-laid the pipe with a new joint, and re-tested. It passed, and we avoided any rework on the rest of the line. The supervisor was happy because we kept the project on schedule.”
- 3
You are working in a deep trench and notice the walls are starting to crumble. What do you do?
Why they ask: This tests your judgement under pressure and commitment to safety.
How to structure your answer: Judgement under pressure: stop work, assess the risk, evacuate if necessary, report to supervisor, and implement controls such as shoring or benching before re-entering.
Example answer
“I would immediately stop work and signal to others to stay clear. I'd assess the situation from a safe distance. If there's any risk of collapse, I'd evacuate the trench and report it to the supervisor straight away. I wouldn't re-enter until the trench has been made safe, either by installing shoring or battering the walls back. I'd also check if anyone else is at risk and make sure the area is barricaded. Safety is always the priority, so I'd follow our site's emergency procedures.”
- 4
What Australian standards and regulations do you follow when installing drainage systems?
Why they ask: This checks your compliance knowledge and attention to legal requirements.
How to structure your answer: List key standards: AS/NZS 3500 for plumbing and drainage, the Plumbing Code of Australia, and state/territory water and plumbing regulations. Explain how you apply them on site.
Example answer
“I follow AS/NZS 3500, which covers the design and installation of plumbing and drainage systems. That includes pipe sizing, gradients, and ventilation. I also comply with the Plumbing Code of Australia and any local water authority requirements, like Sydney Water or Queensland Urban Utilities. On site, that means using approved materials, installing inspection openings at the right spacing, and testing to the required standards. I keep up to date with any changes through my licensing body.”
- 5
Describe your experience with CCTV drain cameras and laser levels. How do you use them to ensure quality?
Why they ask: This assesses your technical proficiency with tools that are central to the role.
How to structure your answer: Explain the tool, how you operate it, and give an example of a time it helped you ensure quality or solve a problem.
Example answer
“I've used CCTV drain cameras to inspect both new and existing lines. For new work, I use them to verify that joints are properly sealed and there's no debris left inside. On existing lines, I use them to locate blockages, cracks, or root intrusion. I also use a pipe laser to set and check the fall of drainage runs. For example, on a commercial project, I used the laser to maintain a consistent grade over a long run, and the CCTV confirmed the alignment was correct before we backfilled. That saved us from having to dig it up again.”
- 6
How do you ensure safety when working in confined spaces or around heavy machinery?
Why they ask: This probes your safety mindset and practical application of procedures.
How to structure your answer: Describe your approach: risk assessment, permits, communication, PPE, and emergency procedures. Give an example of applying it.
Example answer
“Before any confined space entry, I complete a risk assessment and make sure we have a permit if required. I check the atmosphere for gases, ensure there's adequate ventilation, and have a spotter outside. I wear the right PPE, including a harness and gas detector. Around heavy machinery, I make sure I'm visible, use eye contact with operators, and never position myself in a blind spot. For example, when working near an excavator, I always stay out of the swing radius and communicate clearly with the operator. We have daily pre-start meetings to discuss hazards.”