Normal tea all day until 6pm, then Tesco Decaff after.
We buy teabags but use them as single serving sachets - rip the top off and chuck the contents into the teapot. Pour through a strainer but don't drink right to the bottom as some fine tea gets through (but sinks). I find the teabag paper (or the glue/treatments) somehow reacts to make a scum on top of the tea, much better with just the contents, god knows what the scum consists of chemically. Plus the tea's just nicer when it gets to mix properly with the water. A couple of vigorous stirs helps the flavour.
Unlike the coarse tea you can buy as loose, the teabag tea is fine enough to pour straight down the plug hole without messing about. Also just rinse the strainer under the tap. We have our own sewage treatment plant system, it causes absolutely no issues. I'm sure any public system will be fine too. I like to think that the ground leaves probably help the bacteria in there and keep things fresh.