Yes, in most cases you can replace a bath overflow cover and its seal yourself — no licence required. This is a simple maintenance task that involves no pipework alterations, so it falls outside the definition of restricted plumbing work under New Zealand law. With basic tools and the right replacement parts, most homeowners can complete the job in under an hour.
What Is a Bath Overflow and Why Does It Matter?
The bath overflow is the small opening near the top of your bath, usually covered by a decorative plate. Its job is to prevent the bath from flooding if you leave the taps running. Water enters the overflow hole, travels down a pipe inside the bath panel, and drains away. Over time, the cover plate can corrode, crack, or look tired, and the rubber or foam gasket (seal) behind it can harden and fail — allowing water to seep behind the bath surround and cause moisture damage.
Keeping this seal in good condition is important for protecting your bathroom from water ingress, which is a key concern under NZ Building Code clause E3 (Internal Moisture).
Tools and Materials You'll Need
- Flathead and Phillips screwdrivers
- Replacement overflow cover plate (matching your bath style)
- Replacement gasket/seal (foam or rubber, to suit your cover)
- Silicone sealant suitable for wet areas (e.g. a sanitary-grade silicone)
- Clean cloth and mild surface cleaner
- Optional: needle-nose pliers
Replacement overflow covers and gaskets are widely available at Bunnings, Mitre 10, and PlaceMakers. Take your old cover plate with you or measure it carefully — sizes and screw patterns vary between bath brands and styles.
Step-by-Step: Replacing the Overflow Cover and Seal
1. Remove the Old Cover Plate
Unscrew the centre screw (or screws) holding the overflow cover to the bath. Most covers have one or two Phillips-head screws. Once the screws are out, gently pull the cover away from the bath. Set the screws aside — you may be able to reuse them.
2. Remove the Old Gasket
Peel away the old foam or rubber gasket from behind the cover plate or from around the overflow hole on the bath surface. Clean away any old silicone residue, mould, or grime with a mild cleaner and a cloth. Allow the surface to dry fully before continuing.
3. Check the Overflow Pipe Connection
While the cover is off, shine a torch into the overflow hole and have a quick look. You're checking that the overflow pipe is still properly connected inside the bath cavity. If you see signs of significant corrosion, damage, or a disconnected pipe, stop and call a licensed plumber — that repair involves the internal pipework and becomes restricted work.
4. Fit the New Gasket
Place the new gasket against the bath surface, centred over the overflow hole. Some gaskets are self-adhesive; others simply sit in place held by the cover plate. If your replacement kit doesn't include a gasket, a thin bead of sanitary-grade silicone around the overflow hole (not blocking it) can create a watertight seal.
5. Attach the New Cover Plate
Align the new cover plate over the gasket and overflow hole, then insert and tighten the screws firmly — but don't overtighten, as this can crack a plastic cover or distort the gasket. The cover should sit flush and snug against the bath.
6. Wipe Away Any Excess Silicone
If you used silicone, wipe away any squeeze-out with a damp cloth before it cures. Allow the silicone to cure fully (check the manufacturer's instructions — typically 24 hours) before running the bath.
7. Test the Overflow
Fill the bath until water reaches the overflow opening and confirm it drains away freely. Check around the cover plate for any signs of leakage.
Choosing the Right Silicone
Use a sanitary or bathroom-grade silicone that is mould-resistant and rated for wet areas. Brands like Sika offer suitable products. Avoid general-purpose silicones, which may not hold up in a constantly wet environment.
Is This Restricted Plumbing Work?
Simply replacing the cover plate and gasket — without touching any pipes — is not restricted work under the Plumbers, Gasfitters, and Drainlayers Act 2006. You are not altering, repairing, or connecting any sanitary pipework. However, if the overflow pipe itself is cracked, disconnected, or corroded and needs repair or replacement, that work must be carried out by a licensed plumber.
| Task | DIY OK? | Licensed Plumber Required? |
|---|---|---|
| Replace overflow cover plate | ✅ Yes | No |
| Replace overflow gasket/seal | ✅ Yes | No |
| Repair or replace overflow pipe | ❌ No | ✅ Yes |
| Alter drain connections | ❌ No | ✅ Yes |
When to Call a Professional
Call a licensed plumber if you notice any of the following:
- Water staining or rot on the bath panel or surrounding floor — this suggests a longer-term leak that may involve the overflow pipe or waste connections
- The overflow pipe is visibly disconnected, cracked, or corroded inside the cavity
- You're unsure whether your bath surround has suffered moisture damage behind the tiles or lining
- The bath itself is cracked around the overflow hole
A qualified plumber can also check your waste and overflow system is compliant with NZ Building Code clause G13 (Foul Water). You can find trusted local plumbers on tradedirectory.co.nz.
Safety Note
This job involves no electrical work, but always make sure the bathroom is dry before you start, and never use power tools near water. If your bathroom has an electric heated towel rail or in-floor heating, do not interfere with any wiring — that is restricted electrical work under the Electrical Workers Registration Board (EWRB) rules.
Master Plumbers
