What are the blocking plugs made of?

There are three different types of blocking plugs:

1. Black blocker plugs are standard with all Berkey Light water filters and some stainless steel models. The black plugs are made of FDA-approved Buna rubber.
2. Off-white blocking plugs (rubber cork) can be supplied with the Berkey Light models and some stainless steel models. The off-white plugs are made of food-grade M18 pure gum rubber.
3. White blocking plugs (bolt and nut) are used in some stainless steel models. These come with a nut, a screw and two transparent washers. The nut and screw are made of polypropylene. The washers are made of food-grade silicone.

Keep in mind that the water in the lower chamber of your water filter will not touch any of the blocking plugs. This is because the water is filtered before it reaches the lower chamber.