40mm Appliance Waste Trap with Integrated Spigot: UK Buyer's Guide
Under-sink pipework must safely route kitchen sink wastewater alongside high-pressure drainage from your washing machine or dishwasher. This guide covers everything UK homeowners need to know about choosing, buying, and fitting a 40mm appliance waste trap with an integrated spigot nozzle — including how to avoid the most common installation mistakes.
What Is a 40mm Appliance Waste Trap with a Spigot?
A 40mm appliance waste trap with spigot is a specialist under-sink plumbing component that combines two functions in one unit: a standard kitchen sink trap (the water-seal bend that blocks sewer odours) with a dedicated side-entry nozzle for your washing machine or dishwasher drain hose. It replaces the need for a separate P-trap plus an inline T-piece connector.
- All-In-One Drainage: Concurrently processes wastewater from the main sink bowl while providing a secure direct port for appliance discharge.
- Stops Odour Backdrafts: The built-in water seal blocks sewer drain smells from rising back into your kitchen.
- Leak-Free Integration: Keeps all high-pressure appliance connections confined to a single, engineered plastic housing — no separate T-pieces required.
Appliance Trap Types: Which One Do You Need?
Before buying, it helps to understand the three main configurations available at UK plumbing merchants:
| Trap Type | Appliance Connections | Best For | Related Products |
|---|---|---|---|
| Single Spigot (this guide) | 1 appliance (washer or dishwasher) | Kitchen with one built-in appliance | — |
| Twin / Double Spigot | 2 appliances simultaneously | Kitchen with both washer & dishwasher | — |
| Standpipe / Floor-Standing Trap | 1 appliance via standpipe | Utility rooms; appliances without under-sink access | 40mm Standpipe Appliance Trap → |
| Standard P-Trap | No appliance connection | Sink or basin drain only — no appliances | Standard P-Trap Guide → |
Signs You Need to Replace Your Under-Sink Appliance Trap
Under-sink pipework degrades over time due to thermal stress from hot water cycles and chemical exposure from cleaning products. Look out for these critical failure states:
Where to Buy a 40mm Spigot Appliance Waste Trap in the UK
A new 40mm white plastic appliance waste trap with integrated spigot typically retails between £6 and £18 in the UK. Stick to reliable brands such as McAlpine, Floplast, or Viva Sanitary to ensure correct compression tolerances and avoid poorly-moulded nozzle threads.
| Retailer | Stock Status | Top Pick | Link |
|---|---|---|---|
| Screwfix | In Stock | McAlpine 40mm Spigot Trap | View Range |
| Toolstation | Available | Viva Sink Trap with Twin 135° | Check Stock |
| Amazon UK | Available | 40mm Appliance Waste Trap | Check Stock |
Step-by-Step Fitting Guide: 40mm Appliance Waste Trap
Before installing your new appliance spigot trap, confirm you're working with a standard UK 40mm (1½ inch) sink outlet. The process below applies to most under-sink configurations.
Step 1 — Turn Off the Water Supply and Clear Under the Sink
You don't need to isolate the mains supply for trap replacement, but turn off the appliance at its supply point. Place a bowl under the existing trap before loosening any fittings — residual water will drain out. A sink plunger can help clear any blockage before you start.
Step 2 — Remove the Internal Spigot Blanking Disc
New appliance traps are supplied with a solid plastic blanking disc inside the spigot nozzle to prevent leaks if the spigot isn't in use. You must remove this plug before connecting your appliance hose. Use a sharp craft knife or small hacksaw to cut around the disc, then push it out. If you skip this step, your appliance pump will fail to drain and may trigger a fault code. Use PTFE tape on any threaded connections for a leak-free seal.
Step 3 — Fit the New Trap to the Sink Waste Outlet
Slide the compression nut and rubber washer onto the sink waste tail. Hand-tighten only — never use an adjustable spanner on plastic trap threads. The rubber O-ring compresses enough to seal without tools. Check the trap outlet aligns cleanly with your existing 40mm waste pipe run before fully seating the compression joint.
Step 4 — Connect the Appliance Drain Hose
Route your washing machine or dishwasher drain hose in a high loop — it should rise above the spigot entry point before dropping down to connect. This loop prevents back-siphoning. Secure the hose firmly onto the spigot nozzle with a metal jubilee clip or the supplied plastic retaining nut to withstand high-pressure pump cycles.
Step 5 — Test for Leaks
Run the kitchen tap for 30 seconds and inspect all joints. Then run a short wash cycle on your appliance to test under pump pressure. Check around the spigot connection, the sink compression joint, and the trap-to-pipe outlet. If you spot any weeping, re-check the rubber washer position before re-tightening by hand.
💡 Pro Tips for Under-Sink Appliance Traps
- Hand-Tighten Only: Metal pliers on plastic trap threads will crack the fitting body or distort the compression seat — ruining an otherwise good component.
- Pre-Check for Blocked Spigot: If your appliance stops mid-cycle after fitting a new trap, check the spigot tip first. Forgotten blanking discs are the single most common post-installation fault call.
- Weekly Hot Water Flush: Pour near-boiling water down the sink drain weekly. Kitchen traps with an appliance spigot accumulate heavy grease, fats, and fabric softener residue quickly — far faster than a standard basin trap.
- Use PTFE on Threaded Nozzle Connections: Wrap two layers of PTFE tape clockwise around the spigot thread before attaching a threaded retaining nut for a stronger, leak-resistant joint.
- Conical Washers for Older Pipe Runs: If you're connecting to an aged or slightly oval waste pipe run, conical washers provide a more forgiving seal than flat slip washers on worn pipework.
Frequently Asked Questions
Common questions UK homeowners ask when buying or fitting a 40mm appliance waste trap:
The standard UK kitchen sink waste trap diameter is 40mm (1½ inches). This sizing is used by virtually all single-bowl and double-bowl kitchen sinks sold in the UK and connects directly to 40mm waste pipe runs leading to your external drain or soil stack. Bath and shower traps are typically 40mm as well, while basin (bathroom sink) traps are usually 32mm — don't confuse the two.
A single-spigot appliance trap handles one appliance at a time. If you need to drain both a washing machine and a dishwasher into the same trap, you need either a twin-spigot appliance trap (two side-entry nozzles) or a separate standpipe appliance trap for one of the machines. Do not try to T-split a single spigot — the combined pump pressure from two machines can blow the connection.
Yes — and this is the most common installation mistake. New traps are shipped with an internal plastic blanking disc inside the spigot nozzle. This plug exists to prevent leaks if the spigot is unused. You must carefully cut or push out this internal seal before sliding your drain hose on. If left in place, your appliance pump will not be able to drain and will usually trigger a pump or drain fault error on the machine's display.
A P-trap is the basic U-shaped water-seal trap used under sinks, basins, baths, and showers. It creates a water barrier that blocks sewer gases from entering the property. An appliance waste trap is a modified P-trap with an additional side-entry spigot nozzle to accept a washing machine or dishwasher drain hose. It does both jobs — water seal plus appliance drainage — in a single component.
Hand-tight only. The internal rubber or EPDM O-ring compresses adequately under hand pressure to create a watertight seal. Using an adjustable spanner or pliers on plastic trap threads risks cracking the fitting body, stripping the threads, or distorting the compression seat — all of which create leaks rather than preventing them. If a hand-tight joint leaks, check that the rubber washer is correctly seated before adding any further force.
Related Plumbing Products
If you're upgrading your kitchen or bathroom plumbing, these related products from MoreTips are commonly fitted alongside a new appliance trap: