What type of boiler do you currently have?

Take a look at the boiler. Its type should be written on the front.

Otherwise, here are a few rules of thumb:

If you have a cold water tank (probably in the loft) and a hot water cylinder in an airing cupboard, it’s Standard.

If you’ve no cold water tank but you do have a cylinder for your hot water, it’s System.

If you don’t have a cold water tank or a hot water cylinder, it’s likely Combi.

If you’re still unsure, give us a ring on 01924 614 075