This intermediate tank acts as a buffer between the lauter tun or mash tun and the boil kettle. It allows the brewer to visually inspect the clarity of the runoff and control the flow rate without drawing a vacuum on the grain bed, which could cause a stuck mash. Once the liquid collects in this vessel, it is pumped over to the kettle for boiling.
Keep an eye on the sight glass in the underback to make sure the runoff is running clear before we pump it to the kettle.
Also heard as
- grant
- wort grant
Do not mix it up with
- Hopback: An underback collects sweet wort from the mash tun, whereas a hopback infuses hot boiled wort with hop flavor on its way to the chiller.
Related terms
Mash tun
An insulated or heated vessel where crushed grains and hot water are mixed to convert starches to sugars.
Lautering
The process of separating sweet liquid wort from the spent grain solids after mashing.
Wort
The sweet, unfermented liquid extracted from mashed grains that serves as the basis for beer or whisky.