Replacing a kitchen sink strainer waste is one of those plumbing jobs that sits right on the line between DIY and restricted work in New Zealand. The good news is that in most situations a competent homeowner can replace a strainer waste themselves — but only up to a certain point. Understanding where that line is will save you from an illegal repair and a potential insurance headache.
What Is a Sink Strainer Waste?
A sink strainer waste (sometimes called a basket strainer or plug waste) is the fitting that sits in the hole at the bottom of your kitchen sink. It typically consists of:
- A strainer body that fits through the sink hole
- A rubber or silicone gasket and sealing putty or silicone
- A locknut that clamps everything tight from underneath
- A tailpiece (short pipe section) that connects to the trap below
Over time these fittings corrode, crack, or simply start leaking — and replacing them is a common household maintenance task.
What Does NZ Law Say About DIY Plumbing?
Under the Plumbers, Gasfitters and Drainlayers Act 2006, most plumbing work in New Zealand must be carried out by — or under the supervision of — a licensed tradesperson registered with the PGDB. However, there is a specific exemption that allows homeowners to carry out sanitary plumbing maintenance and repairs on their own home.
The key rule is this: you may repair or replace existing fittings like-for-like, provided you are not:
- Extending or altering the drainage layout
- Connecting to or modifying any drain or soil pipe
- Working on a rental property — check with the PGDB and Tenancy Services regarding any restrictions that may apply
Replacing a strainer waste with an equivalent fitting — same size, same position — generally falls within the homeowner exemption. If you are unsure whether your specific situation qualifies, contact the PGDB directly before starting.
Tools and Materials You'll Need
- Replacement strainer waste (match the sink hole diameter — typically 89 mm in NZ kitchens)
- Plumber's putty or neutral-cure silicone sealant
- Adjustable spanner or slip-joint pliers
- Strainer wrench or a pair of needle-nose pliers (to hold the strainer body while tightening)
- Bucket and old towels
- Pipe thread tape (PTFE tape) if your tailpiece has threaded connections
Brand tip: You'll find replacement strainer wastes at Bunnings, Mitre 10, and PlaceMakers. Take your old fitting with you or note the brand and model to ensure compatibility.
Step-by-Step: Replacing the Strainer Waste
1. Turn Off the Water and Clear Under the Sink
You don't need to turn off the water supply to replace a strainer waste (it's not connected to the supply lines), but do place a bucket under the trap to catch any water.
2. Disconnect the Trap
Loosen the slip-joint nut connecting the trap to the strainer tailpiece. Have your bucket ready — water will spill out.
3. Remove the Old Strainer
From underneath, loosen and remove the locknut (a strap wrench or strainer wrench makes this much easier). Hold the strainer body from above so it doesn't spin. Once the locknut is off, push the strainer body up and out through the sink hole.
4. Clean the Sink Hole
Remove all old putty, silicone, and corrosion from around the sink hole. A clean surface ensures a watertight seal.
5. Install the New Strainer
Apply a rope of plumber's putty around the underside of the new strainer flange (or use neutral-cure silicone if your sink is stainless steel or the manufacturer specifies it). Drop the strainer into the hole from above, then fit the rubber gasket, friction ring, and locknut from below. Tighten firmly — but don't overtighten or you risk cracking the fitting.
6. Reconnect the Trap and Test
Reconnect the trap tailpiece, run water, and check carefully for any leaks at the strainer flange and at the trap connections. Dry the area first so you can spot even a small drip.
Common Mistakes to Avoid
| Mistake | Why It Matters |
|---|---|
| Using acid-cure silicone on metal | Corrodes the fitting over time — use neutral-cure |
| Over-tightening the locknut | Can crack plastic components or distort the gasket |
| Skipping the putty/silicone | Leads to leaks around the flange |
| Buying the wrong size | 89 mm is standard but always measure your sink hole |
When to Call a Professional
Call a licensed plumber if:
- The leak is coming from the drain pipe or trap arm rather than the strainer itself
- You discover corroded or damaged pipework under the sink
- You want to reposition the waste outlet or install a double-bowl configuration
- You are a landlord or property manager — check with the PGDB whether a licensed tradesperson is required for plumbing work on rental properties
- You simply aren't confident — a small job done wrong can cause significant water damage
A qualified local plumber can be found quickly on tradedirectory.co.nz. As a rough guide, a tradesperson call-out for a straightforward strainer replacement typically takes under an hour, so labour costs are usually modest.
Safety Note
Always check for leaks thoroughly after completing any plumbing work. Even a slow drip under a kitchen sink can cause mould, structural damage, and health issues over time. BRANZ research consistently highlights moisture as a leading cause of building damage in NZ homes.
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