Principal Mechanical Design Engineer in Havant

United Infrastructure is a dynamic and rapidly expanding business, focused on delivering critical infrastructure projects across the utility and social infrastructure sectors. Our team of highly skilled and hardworking specialists deliver innovative solutions to the complex challenges our clients face.

Our company is split into two business areas:

• Utility Infrastructure – Our team of Utility Infrastructure specialists design, build and maintain critical water, energy (gas), power and telecoms infrastructure for the UK’s largest network owners and operators.
• Social Infrastructure - Our team of Social Infrastructure specialists revitalise homes and communities by carrying out a wide range of work, from retrofit to refurbishment, and maintenance.

Role Purpose

The Principal Mechanical Design Engineer will provide technical leadership for the design and delivery of mechanical systems within water and wastewater infrastructure projects. You will be responsible for ensuring designs meet client requirements, industry standards, performance objectives, and regulatory compliance while guiding multidisciplinary teams through all project stages from feasibility to detailed design and construction support.

Key Responsibilities

• Technical Leadership & Design
  • Lead the mechanical design of water and wastewater treatment assets, including pumping stations, pipelines, treatment plant mechanical equipment, screens, filters, chemical dosing, and sludge-handling systems.
  • Produce and review design deliverables such as P&IDs, specifications, GA drawings, equipment schedules, design calculations, and asset standards.
  • Develop concept, outline, and detailed designs with a strong emphasis on whole-life cost, reliability, and environmental performance.
  • Approve mechanical design documentation and ensure technical quality across project teams.
• Project Delivery
  • Act as the mechanical technical lead on multi-disciplinary projects, coordinating with process, civil, electrical, and ICA engineers.
  • Manage and review design inputs for feasibility studies, optioneering, and value-engineering exercises.
  • Support procurement by preparing technical specifications and evaluating supplier proposals.
  • Provide site support during installation, commissioning, and testing phases as required.
  • Mentor and develop junior engineers and designers, promoting best practices and innovation.
  • Lead design meetings, HAZOPs, design reviews, and client workshops.
  • Ensure designs comply with CDM regulations, health & safety requirements, company standards, and water industry legislation.
• Quality, Compliance & Governance
  • Ensure all outputs meet ISO 9001 quality standards and relevant water industry standards (e.g., WIMES, British Standards, UK Water Industry Specifications).
  • Contribute to continuous improvement of design processes, technical standards, and digital engineering practices.

Skills & Experience Required

• Degree in Mechanical Engineering or equivalent; Chartered Engineer (CEng) or working toward Chartership.
• Significant experience in mechanical design within the water or wastewater sector (utilities, frameworks, EPC, or consultancy).
• Strong technical knowledge of mechanical process equipment used in UK water/wastewater treatment infrastructure.
• Proven capability in leading multi-disciplinary project teams.
• Proficiency with relevant tools (AutoCAD, Solidworks).
• Excellent understanding of UK water industry standards (WIMES, BS EN standards, Water Company asset standards).
• Strong written and verbal communication skills.
• Experience with AMP capital delivery frameworks.
• Experience in digital engineering, model-based design, or advanced simulation.
• Knowledge of sustainability frameworks and low-carbon design principles.
• Supplier engagement and supply-chain integration experience.

Personal Attributes

• Strong leadership and decision-making skills.
• Proactive, innovative, and solutions-oriented.
• Able to work effectively under pressure and manage multiple priorities.
• Excellent client-facing and stakeholder-management abilities.

Typical Deliverables

• Mechanical design reports, technical notes, and option studies.
• P&IDs, layout drawings, equipment sizing and selection calculations.
• Technical specifications and tender documentation.
• Review of vendor drawings and submittals.
• Risk assessments, HAZOP input, and design review documentation.

Additional Information

• Career development – from the moment you join, you’ll be supported to develop, grow your skill set and progress your career the way you want.
• Cultivate – access to our idea and innovation platform, empowering you to drive positive business change.
• Cycle to work scheme.
• Discounts – access to our leisure and shopping discounts and rewards platform.
• Employee networks – opportunity to join our organisation wide employee networks such as our Veteran’s network, Women’s network, and Young People’s network which is dedicated to supporting and retaining employees in the early stages of their careers and empowers young employees and future leaders through Continuous Professional Development (CPD), Social Value and Team Building initiatives.
• Health and Wellbeing Support – access to our employee programme which includes access to a virtual GP and Dentist, mental health support and counselling, fitness and nutrition, and financial and legal advice.
• Health Cash Plan.
• Payroll Giving – the opportunity to donate regularly from your gross pay to support charities of your choice.
• Pension – you will be eligible to join our pension scheme which we will also contribute to.
• Personal Support Network – you will receive a dedicated buddy and mentor and will join an early careers community of peers that will support you forward every step of the way.
• Reward and Award Schemes – access to our long service awards and above and beyond rewards.
• Social Value – you will be encouraged to support social impact activities each year to support charities and local community organisations.