Boil the water and pour over the tea, leaving it to brew for 15 minutes or so (less or more will affect the flavour, so experiment to your taste).
Clean a large two-and-a-half litre jar with boiling water. Once clean, pour the tea into the jar, straining out your chosen tea leaves.
Add the sugar and stir until dissolved. Leave to cool completely before adding the SCOBY and starter kombucha.
Cover the top of the jar with a muslin (cheesecloth) or clean dish towel and fix with an elastic band, leaving in a light place, but not direct sunlight, for about 10 days. The amount of time is dependent on how warm your room is and how sour you like the kombucha, so keep tasting to find the right point. Two weeks is suggested for those that need a ballpark time frame.
Decant the kombucha into two one-litre ceramic flip-top bottles, retaining the SCOBY and a little of the kombucha. In the jar, the SCOBY will live indefinitely, and will kickstart your next batch. At this point you can drink it or do a second fermentation to add more fizz and flavour. If you decide to do a second fermentation, you will need something sweet to allow the process to work its magic successfully. This can include juice or fruit. A reasonable ratio of kombucha to juice/fruit is around 6:1. Have some fun and add ingredients like mangoes and mulberries, or even herbs such as lemon verbena, hibiscus leaves, star anise, fresh ginger or turmeric. Leave the kombucha to ferment for two to three more days.