When you shop for a new basin waste, the first choice you will face is slotted or unslotted. It sounds technical, but it comes down to one simple question about your basin. Getting it right means a waste that drains properly and does not leak.
What Is a Slotted Basin Waste?
A slotted waste has one or more openings, or slots, cut into the side of its body. These slots line up with the overflow channel inside the basin. When water enters the overflow hole near the rim, it travels down the channel, passes through the slots and drains away with the rest of the water.
What Is an Unslotted Basin Waste?
An unslotted waste has a solid body with no openings in the side. It is made for basins that have no overflow, which includes many countertop, vessel and some modern wall-hung basins.
How to Tell Which One You Need
Look at your basin. If there is a small hole or slot near the top rim, usually at the back or front, your basin has an overflow and needs a slotted waste. If there is no hole, choose an unslotted waste.
What Happens If You Choose the Wrong One?
- Unslotted waste in a basin with an overflow – the overflow channel is blocked, so if the basin fills too far, water cannot escape through the overflow and may spill over the rim.
- Slotted waste in a basin without an overflow – the slots have nothing to seal against, so water can escape around the body of the waste and leak underneath the basin.
Can a Waste Be Both?
Some wastes come with a removable sleeve or are sold in both slotted and unslotted versions, so you can use them with either type of basin. Check the product description to see which versions are available.
Does It Affect the Plug Style?
No. Both slotted and unslotted wastes come in the main plug styles, including click-clack, flip top, pop-up and plug and chain. Choose slotted or unslotted first, then pick the style you prefer. Our guide to the parts of a basin waste explains each style.
Free Running Wastes
A free running waste has no plug, so water always drains away. It can be slotted or unslotted, and it suits basins used mainly for hand washing, where you do not need to hold water in the bowl.
Other Things to Check
- Thread size – most UK basins use a 1¼" waste.
- Body length – the waste must be long enough for the thickness of your basin's ceramic.
- Finish – match the visible flange to your tap.
Quick Summary
- Overflow hole in the basin → slotted waste.
- No overflow hole → unslotted waste.
- Then choose your plug style and finish.
Shop Basin Wastes
Browse our basin wastes in slotted and unslotted styles, and see the full waste and traps range for traps to go with them.