Question: what is the difference between slotted and unslotted sink waste?
Answer: Slotted Or Unslotted Basin Waste? If your sink has an overflow you will need a slotted basin waste. ... An unslotted basin waste is watertight, so it won't allow any water which has gone into the overflow back into the waste pipe. Slotted wastes will allow overflow water to be drained, whether the waste is open or not.