There are 2 different and most common types of heating systems. Vented (open to atmosphere, unsealed) and pressurised (sealed). Vented system can be identified with a small header vessel in loft, and it should always be full. This system does not need to be toped up as it is controlled by a ball valve. However, studies show that by sealing your system you can save up to 3% on your heating bills.Pressurised system is getting more and more common these days as people are switching to combination boilers. To top up sealed system you will need to locate filling loop. Will be silver braded hose with a valve either side of the hose. Normally can be found under or near the boiler. Most modern boilers require 0.8bar to operate, however, you would need to check manufacturers instructions on correct pressure (mostly between 1bar-1.5bar). Make sure you are doing this when system is cold. Once filled to correct pressure turn both valves off. Please check out our videos on “How to…”