Overflow weirs can be a common feature in rinse tanks. A PVC tank liner can be made with a weir in place, however, a liner with a built in weir is not the best way to handle such an item.
The small dimensions of the weir are intricate to fabricate. This usually requires the weir to be made from a thinner gauge material than the body of the liner which automatically makes the weir the weakest point of the liner. The different angles of the weir can create stress points that may cause the liner to fail prematurely. Finally, all the material underneath the weir wants to pull away from the sidewall causing problems with the fit of the liner.
A better method for handling weirs is to build a false wall underneath the weir. Wood blocks with plywood overtop can fill in the area underneath the weir and provide a wall face to support the liner. If the weir itself is still to be used the liner simply turns down into the top of the weir and is held in place with Wittclips™. If the weir isn’t to be used the space can be filled in with a block and the flange of the liner simply extended over the block. Either way, the disadvantages of building the weir into the liner are removed resulting in a better fitting and better functioning liner. Furthermore, the fabrication cost of building a weir into the liner is also eliminated.