Any other information about your enquiry? (optional). Speak to your local vaillant installer about direct replacement. Need a job doing? find a trusted tradesperson today with home experts working with checkatrade, providing access to thousands of traders across the uk. Although the checklist should stand you in good stead for most boilers, bear in mind that not all boilers are the same. Combi boiler is a popular choice in uk homes, and for good reason.