You can of course open the steam valve and then turn on the pump to get hot water. This water will have been re-boiled and is not recommended for tea--or so snobby tea drinkers tell me. :)
Or you can set the machine on steam and then steam a jug of cold water to boiling.
However, it is really far more efficient to use a kettle or even a saucepan on the stove for tea.