Waste, Overflow and Installation Basics for Butler Sinks

Key takeaways

• The outlet hole decides which waste fits; a mismatch between waste, overflow and sink is a common cause of leaks.
• Some sinks have an overflow slot and some do not; with an overflow, the waste and connection must be compatible and the tap must not block the slot.
• Beneath the sink, the trap and pipework must fit inside the cabinet, and deep or double bowls leave less room.
• In the UK, water fittings rules apply to plumbing work: England and Wales, Northern Ireland and Scotland each have their own, so confirm with your water supplier.
• A heavy, fragile sink connected to water and drains is not an ideal first project; a qualified installer also helps protect your warranty.

The glamorous part of choosing a butler sink is the bowl, the material and the finish. The less glamorous part, the waste and the overflow, decides whether the sink works well or leaks. This guide explains the general ideas behind wastes and overflows and sets out a sensible approach to installation. It is not a set of plumbing instructions. Plumbing is regulated in many places, and the right way to fit a sink depends on your property, your pipework and the sink's own instructions.

What does the waste do?

The waste is the outlet at the bottom of the bowl that lets water drain away. It consists of a fitting set into the sink, often with a removable plug, and pipework beneath that connects to the drainage system. For butler sinks, the waste is typically larger than on a small modern sink, because the bowl is big and holds a lot of water.

Waste sizes and types

Wastes are made in different sizes, and the diameter of the outlet hole in the sink decides which fittings suit it. Check the specification to find the hole size and any recommended waste type. Common ideas include:

• Plug-and-chain wastes. A traditional arrangement with a plug on a chain, which suits period styling.
• Pop-up wastes. A push-operated plug that opens and closes the outlet without reaching into the water.
• Basket-strainer wastes. A larger outlet with a removable basket that traps food and has a plug. These are popular in kitchens because they stop debris entering the pipework.

Fittings can be made of plastic, brass or other metals, with various finishes. Choose a finish that suits the tap and does not react badly with cleaning products. Ask the seller whether the waste fits the particular sink you are buying, because compatibility is not guaranteed by the fact that both are described as kitchen fittings.

Waste types at a glance

Type	How it works	Worth knowing
Plug-and-chain	A plug on a chain	Traditional arrangement that suits period styling
Pop-up	A push-operated plug that opens and closes the outlet	No need to reach into the water
Basket-strainer	A larger outlet with a removable basket and a plug	Traps food scraps and protects pipework; must suit the outlet size

Does a butler sink need an overflow?

An overflow is a path that carries excess water away if the sink is filled too high, which prevents water from spilling over the rim. Not every butler sink has one, and the type varies.

• Sinks with an overflow slot. The slot is usually near the top of the back wall of the bowl, and water travels through a channel to a connection near the waste. The waste fitting often has to match, with a suitable overflow connection.
• Sinks without an overflow. Some sinks have no overflow at all. This reduces the number of connections, but you must take care not to leave a tap running. Check the specification and ask your installer which rules apply to you.

When an overflow exists, the waste and the overflow connection must be compatible with each other and with the sink. A mismatch is a common cause of leaks. If the sink has a slot, check that the tap does not obstruct it and that the slot is not hidden by tiles or a splashback.

Will the pipework fit inside the cabinet?

Beneath the sink, the waste connects to a trap, which holds a small amount of water to stop smells rising from the drain, and then to the main drainage pipe. All of this must fit within the cabinet. Deep bowls leave less space beneath, so check that the trap and pipework will fit under the sink and that the cabinet has enough room. Double-bowl sinks need two wastes, which increases the space needed.

Which regulations apply, and who should do the work?

Plumbing is more regulated than many people expect. In the UK the work must comply with the water fittings regulations. The official explanatory note to the Water Supply (Water Fittings) Regulations 1999, which apply in England and Wales, says that a person who proposes to install certain water fittings must notify the water undertaker and may not start until it consents, unless the work is done by an approved contractor, who must issue a certificate. Northern Ireland has its own regulations: NI Water says owners, occupiers and installers have a legal duty to meet them, that advance notification is needed for certain work, and that for many jobs done by an approved plumber it is not. Scotland has its own rules too. Ask your water supplier which work needs notice where you live. Building regulations may also apply to drainage and certain alterations. Rules differ by region and change over time, so confirm the requirements for your location with your water supplier, your local authority or a qualified, registered plumber.

Even where a keen householder may legally do part of the work, a sink that is heavy, fragile and connected to water and drains is not an ideal first project. A mistake can lead to leaks, damp, mould and expensive damage to the cabinet and floor. A qualified installer will also know how to protect your warranty, which may depend on correct installation.

How should you plan the installation?

Good planning reduces risk and cost. Think through these points before work begins.

• Read the instructions. Obtain the manufacturer's installation guide and share it with your installer before you buy, if possible.
• Check the cabinet. Confirm that the cabinet is ready, sturdy and the right size, as discussed in our guide on support and weight.
• Choose the tap and waste together. Confirm compatibility with the sink's holes, overflow and outlet.
• Plan the supplies. Make sure the hot and cold supplies and the drain are in a suitable position, or budget the time to move them.
• Allow for sealing. Sealing between the sink and the worktop, and between the sink and the wall, is vital. Your installer will recommend products suitable for your materials.
• Protect the sink. Keep it in its packaging until the cabinet is ready and avoid placing heavy objects in it during building work.

What should you check after installation?

Before the installer leaves, check the following.

• Run the taps and fill the bowl, then release the water. Look underneath for any drips.
• Test the overflow if there is one, under supervision, by letting the water rise to it.
• Check that the plug seals properly and the waste drains freely.
• Look at the seals and joints for gaps.
• Ask for any documentation or certificates that apply in your region.

Revisit the connections after a few days of use. A small drip that appears later is easier to fix than one that has been soaking the cabinet for weeks.

How do you keep the guarantee valid?

Keep your receipts, installation records and the manufacturer's instructions. If something goes wrong, those documents help show that the sink was fitted properly. And if you are unsure about any step, stop and ask a qualified professional before proceeding.

Sources and further reading

• The Water Supply (Water Fittings) Regulations 1999: explanatory note (legislation.gov.uk): that regulation 5 requires a person who proposes to install certain water fittings to notify the water undertaker and wait for consent, that this does not apply to some fittings installed by an approved contractor, and that an approved contractor must issue a certificate.
• NI Water: Water Fittings Regulations: that in Northern Ireland owners, occupiers and installers have a legal duty to meet the regulations, that advance notification is needed for certain work unless an approved plumber does it, and that breaching them is a criminal offence.