Commonly used with certain traditional style basins, a chainstay waste contains elements you may be familiar with from older style bathrooms and public toilets. In recent years, this type of waste, which includes a plug on the end of a chain, has been overtaken by modern designs in terms of popularity, as the plug chain can look a little untidy when not in use.
Chainstay wastes are only suitable when your chosen basin comes with a pre-drilled chainstay hole. They are almost always slotted, for use with an overflow.
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