Recently we bought a new Bezzera B2016 1 group for our newly renovated bakery. As the building is not yet ready I have had it at home for about a week and I’m training myself and the staff up on it.
I have mostly been making espressos and milk drinks so I haven’t been using the hot water spiggot much. A few days ago though I made an Americano and noticed it had a nasty plastic taste. A bit of investigation later and it’s because of the water from the hot water spiggot. Tastes a bit like burnt plastic. It’s not extremely strong but it’s enough to completely ruin the taste of the coffee and I’m sure it’s not healthy to drink.
I also tested water directly from the group head and it tastes absolutely fine. Then I condensed some water from the steam wand it tastes ok, I think. Harder to test because I couldn’t condense much water.
I contacted the shop who sold it to me and they suggested draining the tank and refilling. However I doubt this can be the solution as the water from the group head tastes fine.
I’m also sure the water going in is fine. While I have it here, it’s drawing water from 30L containers that we fill at a local water processing plant - they are very high quality and provide data for their water. I was assured by the shop that it’s fine to run the machine this way until it’s plumbed in and that many smaller cafes around here (where tap water is not drinkable) actually permanently run their machines this way. Of course I did taste the water directly from the bottle too and it’s fine. Delicious in fact 
However the hot water spiggot still tastes terrible and I have flushed at least a couple of liters through it. Is this normal for a new machine? How much water should I flush?