Installing a Food Waste Disposer: A Step-by-Step Guide
The process of fitting a food waste disposer involves several distinct phases, from removing the existing unit to ensuring proper drainage and electrical connections. Adhering to these steps ensures a successful installation.
1. Dismantling the Existing Disposer Unit
Begin by isolating the power supply to the current disposer. This involves either unplugging the unit or, for a hardwired setup, switching off the corresponding circuit breaker at your main consumer unit.
- Proceed to detach the existing food waste disposer by disconnecting all associated drain pipework.
- Next, separate the disposer unit from the flange assembly secured to the underside of the sink.
- Finally, remove the entire flange assembly from the sink’s drain opening.
2. Preparing the Sink Area Plumbing and Wiring (Optional for New Installations)
If this is a completely new installation of a food waste disposer, you have the option to undertake the necessary plumbing and electrical setup yourself or engage a qualified plumber and electrician.
- Electrical Setup: Install a dedicated, switch-controlled 13-amp 230-volt switched fused spur outlet beneath the kitchen sink, positioned close to where the disposer will reside. Ensure proper earthing.
- Plumbing Setup: Arrange for a P-trap (the curved drainpipe) to be situated within 125mm of the sink’s drain outlet.
3. Fitting the Drain Assembly and Mounting Ring
The new flange assembly, which will anchor the disposer beneath the sink, is installed next.
- Sealant Application: Apply a consistent, approximately 12mm thick, bead of plumber’s putty (or a suitable silicone sealant) around the perimeter of the drain opening from the top side of the sink.
- Flange Insertion: Insert the new disposer sink flange into the drain hole, again, from the sink’s top surface.
- Firm Seating: Press the flange down firmly into the plumber’s putty to create a robust seal.
- Under-Sink Components: From beneath the sink, slide the fibre gasket and the metal triangular attachment ring upwards onto the flange’s extended tailpiece.
- Securing the Ring: Lock the ring into position by snapping the circular clip spring or retaining ring into the designated groove on the flange tailpiece.
- Helpful Hint: An assistant is invaluable at this stage to firmly hold the sink flange from above while you work underneath.
4. Tightening the Mounting Ring Assembly
Proceed to tighten the entire mounting assembly using its three mounting screws.
- Even Pressure: Turn each screw incrementally and alternately to apply consistent, even pressure around the ring.
- Optimal Tightness: Continue tightening the screws until the sink flange is firmly seated against the underside of the sink and excess plumber’s putty begins to extrude.
- Clean-up: Wipe away any extruded plumber’s putty from around the drain opening inside the sink using a clean cloth.
- Helpful Hint: The slight extrusion of plumber’s putty indicates a secure seal. Exercise caution not to overtighten and expel all the putty.
5. Connecting the Disposer’s Power Cable
Before physically mounting the food waste disposer, its electrical power cable must be connected.
- Access Electrical Compartment: Remove the electrical cover plate located on the bottom of the disposer unit.
- Install Cable Gland: Install a cable gland (strain relief fitting) into the designated hole where the power cable will enter.
- Secure Fitting: Tighten the fitting nut using pliers.
- Feed Cable: Thread the exposed wire end of the power cable through the cable gland.
- Clamp Cable: Secure the cable by tightening the cable gland clamp onto the cord with a screwdriver.
- Wire Connections (UK Colour Code): Using appropriate connector blocks or wire nuts, connect the brown (Live) lead from the disposer to the power cable’s brown (Live) wire, the blue (Neutral) lead to the power cable’s blue (Neutral) wire, and the green/yellow (Earth) lead to the power cable’s green/yellow (Earth) wire.
- Close Compartment: Carefully tuck the connected wires into the disposer’s electrical box and re-secure the cover plate.
6. Connecting a Dishwasher (If Applicable)
In certain setups, the dishwasher’s waste water drains through the food waste disposer. If this applies to your installation:
- Locate Inlet: Find the dishwasher inlet nipple positioned near the top of the disposer’s grinding chamber.
- Remove Plug: Insert a screwdriver into the nipple and firmly tap the screwdriver with a hammer (as if using a chisel) to dislodge the internal plug. The plastic disc will drop into the disposer’s grinding chamber.
- Retrieve Plug: Reach inside the disposer unit from the top opening and retrieve the dislodged disc.
7. Mounting the Food Waste Disposer
Proceed to attach the food waste disposer unit to the sink:
- Align Unit: Orient the disposer by aligning its top collar with the three mounting lugs on the sink mounting assembly already installed.
- Engage Lugs: While holding the disposer in position, rotate its top collar so that the three mounting lugs engage into the corresponding mounting collar on the underside of the drain fitting.
- Initial Securement: Rotate the collar just enough to hold the disposer in place. Avoid fully tightening it at this stage, as minor positional adjustments might be necessary before final securing.
8. Connecting the Drain Pipework
Fasten the rubber discharge pipe to the disposer unit using its gasket and retaining screws.
- Position Disposer: Rotate the disposer unit to ensure its discharge pipe aligns correctly with the sink drain’s waste trap (P-trap or U-bend).
- Connect Dishwasher Line (If applicable): Slide the dishwasher hose onto the disposer’s nipple.
- Secure Hose: Fasten it securely with the manufacturer-provided clamp.
9. Final Locking of the Disposer Unit
Securely lock the food waste disposer unit to the sink mounting assembly by firmly tightening the rotating cam collar on the disposer. This can be achieved using either a screwdriver for leverage or a specialised wrench that may have been supplied with the unit. You will likely feel a distinct click as the disposer unit locks into its final position.
10. Verifying Leak-Free Operation
Perform a thorough check of your work:
- Water Test: Restore the water supply and run cold water through the disposer unit. Carefully inspect all plumbing connections for any signs of leaks. If leaks are present, gently tighten the loose drain connections.
- Power On: Plug the disposer into the wall outlet (if applicable) and ensure the circuit power is restored at the consumer unit.
- Functional Test: With cold water running, activate the food waste disposer and introduce a small amount of appropriate food scraps into the drain to confirm proper operation.
Food Waste Disposer Installation Best Practices
A few straightforward tips can expedite and simplify the installation process, while also enhancing safety:
- Always place a bucket beneath the pipework when disconnecting it to capture any residual water.
- Ensure your chosen new food waste disposer unit is compatible with the electrical outlets available (e.g., standard 13-amp plug).
- Fill the sink with water to perform a thorough check of the sink drain seal before running the disposer.
- Verify that the disposer’s electrical line is correctly earthed.
- Crucially, never attempt to earth an electrical wire to a gas line.
- If you are not entirely comfortable undertaking the electrical or plumbing work yourself, engage a qualified electrician and plumber.
- To prevent odours, periodically grind up a sliced lemon every few days or weeks.
Frequently Asked Questions
Is an electrician required for food waste disposer installation?
An electrician is not typically required to install a food waste disposer if a dedicated, switch-controlled, and properly earthed 230V circuit (e.g., a fused spur) is already present and correctly wired to the sink area. If such a circuit is not installed, or you are unsure, you can either install it yourself if you possess the necessary electrical qualifications and experience, or you can hire a qualified electrician. Note that significant electrical alterations may require notification to your local building control body.
How long does a plumber take to install a food waste disposer?
A plumber can typically install a food waste disposer in approximately one hour or less, provided that the necessary plumbing connections are already in place and in good condition.
Do you need a special sink to install a food waste disposer?
No, a special sink is not generally required to install a food waste disposer. Food waste disposers can be fitted to nearly all standard single-basin or double-basin kitchen sinks that have a standard 90mm (3.5 inch) sink hole.