Installing a garbage disposal, often called a food waste disposer in the UK, can be a great way to improve kitchen hygiene and convenience. While it’s a DIY-friendly project for those comfortable with basic plumbing and electrics, it’s crucial to prioritise safety and ensure all electrical work complies with UK regulations (BS 7671: IEE Wiring Regulations). If you’re not confident with electrical wiring, it’s always best to consult a qualified electrician.
Here are 6 easy steps to guide you through the installation, assuming you’re replacing an existing sink waste or fitting a new one. Always refer to your specific food waste disposer’s manufacturer’s instructions as models can vary.
Tools and Materials You’ll Likely Need:
- New food waste disposer unit
- Plumber’s putty or silicone sealant
- Screwdriver (Phillips and/or flathead)
- Adjustable wrench or pipe wrench
- Pliers
- Bucket and rags
- Hacksaw (if you need to cut pipes)
- Electrical wire nuts (if hardwiring) and electrical tape
- Safety goggles and gloves
- Optional: Air switch kit (for a worktop mounted switch, rather than a wall switch)
How To Install a Food Waste Disposer in 6 Easy Steps (UK Focus)
Step 1: Prepare Your Work Area & Ensure Safety
- Clear Under the Sink: Remove everything from the cupboard beneath your sink to give yourself ample space to work.
- Turn Off Power: Crucially, locate your consumer unit (fuse box) and switch off the circuit breaker for your kitchen or the specific circuit for the existing waste disposal unit (if applicable). If you’re unsure, switch off the main incoming power.
- Turn Off Water Supply: Close the hot and cold water isolation valves under the sink.
- Place a Bucket: Position a bucket directly under the sink waste to catch any residual water or debris when you disconnect the plumbing.
Step 2: Remove Your Existing Sink Waste (If Applicable)
- Disconnect Existing Plumbing: Use an adjustable wrench to loosen the slip nuts connecting the existing sink waste and trap (U-bend or P-trap) to the sink drain and the main waste pipe in the wall.
- Remove Old Waste: Carefully remove the existing sink waste and trap. There might be some sealant or putty to scrape off from around the sink opening. Clean the sink opening thoroughly.
Step 3: Install the New Mounting Assembly
This is the core attachment to your sink. Different disposers may have slightly different mounting mechanisms, so refer to your manufacturer’s specific instructions.
- Apply Sealant: Roll a thin bead of plumber’s putty (or apply silicone sealant) around the underside rim of the new sink flange (the metal ring that goes into the sink hole).
- Insert Sink Flange: Insert the sink flange from the top of the sink into the drain opening. Press down firmly to create a seal and squeeze out excess putty/sealant. Wipe away the excess from the sink side.
- Assemble Underneath: From underneath the sink, slip on the various gaskets, backup rings, and mounting rings onto the exposed sink flange, following your manufacturer’s diagram.
- Secure: Hand-tighten the lower mounting ring. Then, use the provided screws or a special wrench (often included with the unit) to tighten the assembly firmly against the sink. Ensure the sink flange is secure and doesn’t move.
Step 4: Connect the Disposer Unit to the Mounting Assembly
- Prepare the Disposer: If your unit has a dishwasher inlet, you’ll need to knock out the internal plug with a screwdriver and hammer. Ensure the plug is removed from inside the disposer unit.
- Align and Attach: Carefully lift the disposer unit and align its opening with the mounting assembly you just installed. Most units have three mounting tabs that fit into slots on the mounting ring.
- Twist to Lock: Twist the disposer unit (often clockwise) to engage the mounting tabs with the slots, locking it into place. This can sometimes require a bit of force or a special tool provided by the manufacturer. Once engaged, the unit should hang securely.
Step 5: Connect the Plumbing (Discharge Pipe)
- Attach Discharge Elbow: Connect the discharge elbow (the curved pipe) to the outlet of the disposer unit using the provided gasket and bolts/screws. Ensure a good seal.
- Connect to Waste Pipe: Adjust and connect the other end of the discharge elbow to your existing waste pipework, usually leading to a P-trap or U-bend. You may need to cut existing pipes with a hacksaw or use flexible connectors to get the correct alignment. Ensure there is a slight downward slope for proper drainage.
- Secure Connections: Use slip nuts and gaskets to tighten all plumbing connections. Do not overtighten, as this can crack plastic pipes.
Step 6: Electrical Connection & Testing
WARNING: If you are not a qualified electrician or uncomfortable with electrical wiring, HIRE A PROFESSIONAL.
- Connect Electrical Wires:
- If replacing an old unit: Disconnect the old unit’s wiring and connect the new disposer’s wires (Live, Neutral, Earth) to the corresponding wires from your electrical supply. Use appropriate wire nuts or a suitable junction box/connector block. Ensure the appliance is properly earthed.
- If new installation: The unit should ideally be connected to a switched, fused spur unit (often 13 amp) for easy isolation and safety. Alternatively, it might plug into a dedicated, unswitched socket under the sink that is controlled by a wall switch or an air switch. Follow the wiring diagram in your manual precisely.
- Secure Wiring: Ensure all electrical connections are secure and properly insulated with electrical tape where necessary. Cable tie or secure the wiring to prevent it from hanging loosely or getting snagged.
- Test for Leaks: Restore the water supply. Run cold water into the sink. Check carefully for any leaks at all plumbing connections. Tighten gently if needed.
- Test the Disposer: Once you’re confident there are no leaks from the plumbing, restore power at the consumer unit. Turn on the cold water flow in the sink and then switch on the food waste disposer. Listen for any unusual noises.
- Final Check: Run water for about 15 seconds after turning off the disposer to ensure all waste is flushed through. Clean up any excess putty or sealant.
Congratulations! You have successfully installed your food waste disposer. Remember to always consult your specific model’s manual for detailed instructions and safety warnings.