Appendix D - Building a Mash/Lauter Tun
D.1 Building the Manifold
The heart of the lauter tun is the wort collection manifold. It can be made of either soft or rigid copper tubing . Choose the form to suit your cooler and design. In a round cooler, the ideal shape is a circle divided into quadrants. See Figure 162. In a rectangular cooler, the ideal shape is rectangular with several legs to adequately cover the floor area. When designing your manifold, keep in mind the need to provide full coverage of the grainbed while minimizing the total distance the wort has to travel to reach the drain. Figure 163 illustrates this issue for a rectangular cooler.
Figure 163 - Difference in tubing length and area coverage for cylindrical cooler. Wort at point "A" has a comparatively long distance to travel to the drain.
Figure 164 - Rectangular manifolds. The manifold on the right could be improved by providing a more direct means for wort at point "A" to reach the drain.
In addition, it is very important to avoid channeling of the water down the sides from placing the manifold too close to the walls. The distance of the outer manifold tubes to the cooler wall should be half of the manifold tube spacing or slightly greater. This results in water along the wall not seeing a shorter path to the drain than wort that is dead center between the tubes.
Figure 165 - Design to make the best use of the space. The manifolds should fit the bottom of the cooler, covering the most area possible and not move around. Also, plan to space the manifold at half the pipe-spacing-distance to the wall to avoid channeling. (More on this in the next section.)
The transverse tubes in the rectangular tun should not be slotted to prevent channeling. The longitudinal slotted tubes adequately cover the floor area without the transverse tubes help. The slots can face up, down or to the side; hydraulically, it makes no difference. In a circular tun, the same guidelines apply but the transverse tubes can be slotted where they are away from the wall.
Figure 166 - A useful design for rigid tubing manifolds. Solder or crimp the indicated connections but leave the other connections for the straight tubes free. This allows easy disassembly for removal and cleaning. Be sure to completely clean the manifold of flux from soldering before use.