Why Is My Shower Leaking? Common Causes in New Zealand Bathrooms

A leaking shower is one of those bathroom problems that often starts small: a damp patch near the shower door, a bead of water appearing outside the tray, a swollen skirting board, or a musty smell that does not go away.

For many New Zealand homeowners, the tricky part is not noticing the leak. It is working out where the water is actually coming from.

A shower leak may be caused by something simple, such as a worn door seal or tired silicone. But it can also point to a deeper issue behind the liner, around the tray, through a wall junction, or near plumbing penetrations. Reddit discussions in New Zealand DIY communities often show the same pattern: homeowners see water at the edge of the shower, try adding silicone, and then realise the actual leak may be hidden behind the frame, liner or wall connection.

This guide explains the most common causes of shower leaks in New Zealand bathrooms, what to check first, and when a simple reseal may not be enough.

Why shower leaks are common in New Zealand bathrooms

Bathrooms are high-moisture spaces. Every shower creates steam, splash water and condensation. If moisture is not controlled properly, it can affect silicone joints, shower frames, wall linings, flooring and nearby cabinetry over time.

The New Zealand Building Code section on internal moisture requires wet-area surfaces to be impervious, easily cleaned and ventilated in a way that supports health and safety. It also focuses on preventing water from penetrating behind linings or into concealed spaces.

In real homes, however, problems often appear because of age, movement, failed sealant, poor installation details, blocked drainage paths, or moisture that has been allowed to sit in the same area for years.

A shower may look fine on the surface while water is quietly tracking behind the frame or liner.

The most common causes of shower leaks

1. Failed silicone around the shower

Silicone is often the first thing people blame, and sometimes they are right. Over time, silicone can shrink, split, lift, go mouldy or lose adhesion.

Common signs include:

• black or mouldy silicone

• small gaps or cracks

• water appearing from one corner

• loose or peeling sealant

• silicone that feels soft, sticky or detached

A New Zealand Reddit user described a leak where silicone between the liner and frame had failed, allowing water to track below the shower and become visible underneath the floor area.

However, adding more silicone on top is not always the right fix. If old silicone is failing, it usually needs to be removed properly, the area dried and cleaned, and then resealed with the correct bathroom-grade sealant.

2. Missing or damaged shower door seals

If water is leaking from the bottom of the shower door, the problem may be a missing, damaged or poorly fitted seal strip.

This is especially common with glass shower doors. A small gap under the door can let a surprising amount of water escape, especially if the shower head points toward the opening.

Signs include:

• water pooling outside the door after every shower

• water escaping only when the shower is running

• visible gap below the glass door

• brittle, yellowed or loose plastic seal

• door seal not touching the tray properly

In one Reddit discussion about water leaking under a shower door in a new build, the issue appeared to be related to the bottom door seal being missing.

For this type of leak, replacing the seal strip may be enough, provided the tray, glass and door alignment are correct.

3. Water tracking behind the shower frame

One of the most frustrating shower leaks is when water appears outside the shower, but the visible silicone looks mostly fine.

In this case, water may be entering behind the frame, through a junction, or around the liner. It may travel sideways or downward before appearing somewhere else.

This is why the visible leak point is not always the source.

Possible causes include:

• gaps behind the frame

• poor sealing at the tray upstand

• incorrect liner installation

• water trapped behind a sealed section

• movement between wall, tray and frame

Some Reddit discussions mention leaks at the corner where shower glass meets the wall, with users questioning whether the liner is sealed correctly at the base where it meets the tray.

This is where DIY patching can become risky. If water is already behind the liner, sealing the outside may trap moisture rather than solve the problem.

4. Tray, liner and wall junction problems

A shower tray is not just the visible base you stand on. Many acrylic shower systems rely on the correct relationship between the tray, wall liner, upstand and frame.

If that system was not installed correctly, or if it has moved over time, water may escape into areas it should never reach.

Warning signs include:

• soft flooring near the shower

• swollen skirting or vanity panels

• bubbling paint

• water marks on the ceiling below

• musty smell

• repeated silicone failure in the same spot

In Reddit conversations, users often ask whether the bottom of a shower liner should be sealed, whether gaps are drainage paths, or whether adding silicone may block water that needs to escape.

This is an important point: not every gap should automatically be filled. Some shower systems are designed with drainage paths. Blocking them can make the problem worse.

5. Leaks around the mixer or plumbing penetrations

If water appears near a wall but not obviously from the door or tray, the leak may be related to the mixer, shower rose, pipework or wall penetration.

Signs include:

• leak occurs even when water is not splashing near the door

• dampness around mixer area

• water marks on the wall behind or below the shower

• moisture visible from the other side of the wall

• pressure changes or dripping from fittings

These leaks need more care because the source may be behind the wall. A licensed plumber or experienced bathroom professional should check it, especially if there is any sign of hidden water damage.

Shower door seal vs silicone failure

A simple way to start is to separate the problem into two questions:

If the leak is clearly from a door seal, repair may be simple.
If water may be behind the liner or wall, treat it seriously.

When resealing may be enough

Resealing may be enough when:

• the shower is otherwise in good condition

• the tray is solid and not cracked

• the leak is clearly from a small silicone gap

• there is no swelling, softness or musty smell

• the area can be fully dried before resealing

• the correct bathroom-grade mould-resistant silicone is used

A proper reseal usually means removing old silicone first. Applying new silicone over old, dirty or wet sealant often fails quickly.

Before resealing, the area should be cleaned, dried and checked for movement. If the same joint keeps failing, there may be a bigger installation or movement issue.

When you may need more than silicone

You may need more than a reseal if:

• the leak returns soon after resealing

• water is visible under the floor or outside the bathroom

• wall linings are swollen or soft

• there is mould behind trims or around the liner

• the shower frame feels loose

• the tray has movement or cracking

• there is water damage to nearby cabinetry or flooring

At this point, the question is no longer just “How do I stop the water today?”
It becomes: Has water already entered a concealed space?

New Zealand guidance around wet areas places importance on impervious, cleanable surfaces and moisture control because hidden water can cause long-term damage when it gets behind linings or into concealed areas.

What to check before buying a new shower box

If your existing shower is old, leaking repeatedly or poorly sized, replacing the shower box may be more practical than patching it again.

Before buying a new shower box, check:

1. Existing shower size

Measure the available width, depth and height. Do not assume the current shower size is standard.

Common shower box sizes include:

• 800 × 800mm

• 900 × 900mm

• 1000 × 1000mm

• 1200 × 800mm

For small bathrooms, a sliding door or round corner design may save space.

2. Door opening clearance

A swing door needs enough room to open safely.
A sliding door can be better for compact bathrooms, rental properties or tight layouts.

3. Wall condition

If the wall behind the old shower has moisture damage, it should be repaired before installing a new shower enclosure.

4. Plumbing position

Check where the mixer, shower outlet and waste are located. Moving plumbing can add cost, so many renovations keep the layout similar.

5. Tray and waterproofing details

A shower is only as good as its installation. The tray, wall junctions, frame and seals all need to work together.

How to reduce the risk of future shower leaks

A better shower setup is not just about the enclosure. It is also about moisture management.

BRANZ notes that internal moisture indicators include condensation on mirrors and tiles, mould growth on ceilings and walls, and musty smells. It also recommends that kitchen and bathroom renovations include mechanical ventilation where appropriate.

To reduce future problems:

• use an extractor fan vented outside

• wipe down glass and silicone after showers

• keep door seals clean and flexible

• replace damaged seals early

• avoid letting mould build up on silicone

• check corners and junctions regularly

• repair small leaks before they reach cabinetry or flooring

• choose easy-clean glass, tiles and fittings where possible

EECA also notes that good ventilation helps prevent humidity build-up, dampness and mould, especially in bathrooms and kitchens.

Repair or replace: how to decide

A simple leak can sometimes be fixed in an afternoon.
A hidden leak should not be ignored.

FAQ

Can I just add more silicone to a leaking shower?

Sometimes, but not always. If the old silicone is dirty, wet, mouldy or loose, new silicone may not bond properly. It is usually better to remove the old silicone, dry the area, clean it properly and then reseal. If water is behind the liner or frame, adding silicone on the outside may trap moisture.

Why is water coming out from the shower corner?

Corner leaks are often caused by failed silicone, frame junction issues, tray movement or water tracking behind the liner. The visible corner may not be the original source of the leak.

Is a leaking shower door serious?

If water only escapes from a missing bottom seal, it may be a simple fix. But if water is reaching flooring, skirting, walls or cabinetry, it should be checked quickly.

Should the bottom of a shower liner be sealed?

It depends on the shower system. Some designs include drainage paths, and sealing the wrong area may trap water. If you are unsure, check the manufacturer’s installation instructions or ask a bathroom installer.

When should I replace my shower instead of repairing it?

Replacement may make sense if the shower is old, leaking repeatedly, has hidden water damage, or no longer suits the bathroom layout. It may also be more cost-effective if multiple parts are failing at once.

What shower box is best for a small New Zealand bathroom?

For smaller bathrooms, sliding doors, round corner showers and compact square shower boxes are often easier to work with because they reduce door swing clearance issues.

Final thoughts

A leaking shower is not just an inconvenience. In a New Zealand bathroom, it can quickly become a moisture problem affecting walls, flooring, cabinetry and indoor air quality.

Start with the simple checks: door seals, silicone, corners and visible gaps. But if the leak keeps returning, or if there are signs of hidden moisture damage, treat it as more than a surface problem.

The best long-term fix is a shower setup that is correctly installed, properly sealed, easy to clean and supported by good ventilation. Whether you are resealing an existing shower or planning a full replacement, the goal is the same: keep water where it belongs and protect the rest of your bathroom from hidden moisture damage.