How can plumbing problems be mitigated? Plagued by nuisance calls and texts? use our tool to report the culprits. Sign up now to stay updated on the latest news and offers! How to get the best hearing aid. What type of tradesperson do you need? The first, and most common type, is the gas combination boiler (aka the 'combi') unlike boilers of old, a combi runs both your central heating and your hot water from one unit.