Public Health Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Most Public Health Engineer interviews in the UK follow a pattern, and knowing it beats guessing. Below are eight questions from our bank of 12, each with a note on what the interviewer is really after.

Eight Public Health Engineer interview questions, and what the interviewer is thinking

1. How do you size cold water storage and booster pumps for a multi-storey building, and which standards do you follow?

Why they ask: Water services sizing is central to the role.

2. What does a public health engineer do on a typical project, and why does this speciality appeal to you?

Why they ask: It tests understanding of a specialist branch within building services.

3. How do you design a hot water system to control Legionella risk?

Why they ask: Legionella control is a critical safety obligation.

4. How would you design the below-ground foul and surface water drainage for a new building, and what regulations apply?

Why they ask: Drainage design is a core expertise of the role.

5. What is involved in designing a sprinkler or wet riser system, and who would you coordinate with?

Why they ask: Fire protection is within the public health remit.

6. On site, the plumbing contractor has installed hot water pipework with several long dead legs, saying they are easier to install. What do you do?

Why they ask: This tests practical enforcement of a safety-critical requirement.

7. Tell me about a time you resolved a design problem on a water or drainage system.

Why they ask: Problem solving on real systems is central.

8. A water company says the mains pressure and flow at a site is much lower than your design assumed. How do you proceed?

Why they ask: Supply data uncertainty is a common real-world issue.

A sample answer to question 1

How do you size cold water storage and booster pumps for a multi-storey building, and which standards do you follow?

I start by calculating the design flow rates using loading units from BS EN 806-3 and CIBSE Guide G, taking account of the type of building and the probability of simultaneous use. For storage, I normally provide between 12 and 24 hours of supply in line with guidance, though for hospitals or high-risk buildings I look at greater resilience. Break tanks need to meet the Water Supply (Water Fittings) Regulations 1999, with air gaps, covers, insect screens and turnover so water does not stagnate, which also supports Legionella control under HSE L8. For boosting, I select a duty and standby set with variable speed drives, sized for peak flow at the required pressure at the highest outlet, and check pump curve, NPSH and pressure vessel sizing. Pipework is sized against velocity limits, generally 1.5 to 2 metres per second, to limit noise and erosion.

Common mistake to avoid: Ignoring stagnation risk; Sizing for total connected load

Want the rest?

Full model answers, key points and common mistakes for all 12 questions are on the Public Health Engineer interview questions page. The first five are free, no sign-up needed.