The same shower can feel superb in one house and weak in the next, and the water system is almost always the reason. This guide shows how to tell whether you have a gravity-fed, combi or unvented system, then which shower types suit each: power, gravity-pumped smart, mixer, high-pressure smart or electric. It includes a worked four-bathroom cost comparison and Aqualisa picks with prices and stock checked on 20 October 2026.