Call us today, and find out why. The advance combi boiler has been designed with efficiency and reliability at the forefront of our minds compact yet powerful the advance combi can deliver up to 13.3 litres per minute of instant hot water. Here are a few questions to think about before you have a conversation with your installer. If your property is flooded by water coming from the road please call us on 0121 368 1177. Bristol drains are your professional drain and.