How to Spot Signs of Poor Plumbing Work in Your Home

Poor plumbing work can hide behind walls and under floors for years before causing serious — and expensive — damage. Whether you've just bought a home, are renting out a property, or simply want peace of mind, knowing what to look for can save you thousands. Here's how to spot the red flags of substandard plumbing in a New Zealand home.

Why Poor Plumbing Is a Serious Problem

In New Zealand, plumbing work is restricted work under the Plumbers, Gasfitters and Drainlayers Act 2006. This means most plumbing, drainlaying, and gasfitting must be carried out by a licensed tradesperson registered with the Plumbers Gasfitters & Drainlayers Board (PGDB). Unlicensed or poorly executed plumbing can breach the NZ Building Code (particularly clauses G12 – Water Supplies and G13 – Foul Water), void your home insurance, and create health and structural risks.

Visual Signs to Look For

Water Stains and Moisture Damage

One of the most obvious signs of a plumbing problem is water staining on ceilings, walls, or cabinetry — particularly around bathrooms, kitchens, and laundries. Look for:

• Yellow or brown ring-shaped stains on ceilings below bathrooms
• Bubbling, peeling, or blistering paint on walls near pipes
• Soft or spongy areas on timber floors near toilets, showers, or sinks
• Mould or mildew growth in areas that should be dry

These can indicate leaking joints, poor waterproofing, or incorrectly installed fixtures.

Dodgy Pipe Connections and Fittings

If you can access under-sink areas, in the roof space, or in a subfloor, take a look at the pipework. Warning signs include:

• Mismatched pipe materials joined without proper transition fittings (e.g., copper joined directly to galvanised steel)
• Excessive use of thread tape or sealant to compensate for poor-fitting joints
• Pipes that sag, are unsupported, or run at incorrect gradients — drain pipes need a consistent fall to work properly
• Push-fit or compression fittings used in concealed locations where they shouldn't be
• Visible corrosion, green staining on copper, or rust on steel pipes

Low or Inconsistent Water Pressure

Low water pressure throughout the house — or pressure that fluctuates unexpectedly — can point to undersized pipework, partially blocked pipes, or incorrect installation. If only one fixture is affected, it may be a blocked aerator or faulty valve, but widespread pressure issues warrant investigation.

Slow Drains and Gurgling Sounds

Drains that empty slowly or make gurgling noises often indicate:

• Incorrect pipe gradients (too flat or too steep)
• Missing or incorrectly installed air admittance valves or vent pipes, which can cause siphoning and allow sewer gases into the home
• Poor drain alignment or connections that trap debris

Gurgling from multiple fixtures at once is a particular red flag for a systemic drainage problem.

Running or Constantly Cycling Hot Water

If your hot water cylinder runs constantly or your water meter ticks over when all taps are off, you likely have a leak somewhere in the system. A simple test: turn off all water-using appliances and check if your water meter dial is still moving.

Signs of Illegal or Unlicensed Work

Unlicensed plumbing is unfortunately not uncommon in New Zealand, particularly in older homes or properties with a history of DIY modifications. Look out for:

• No building consent for work that required one — check your LIM report or ask your council. Note that some minor plumbing work may be exempt under Schedule 1 of the Building Act, but always confirm with your local council.
• Fixtures or fittings that don't comply with AS/NZS standards (e.g., non-compliant tapware or water heaters)
• Hot water cylinders without a temperature and pressure relief (TPR) valve correctly installed and piped to a safe discharge point
• Gas appliances connected with flexible hose in concealed spaces — this is a serious safety hazard

BRANZ provides excellent technical guidance on building and plumbing standards that can help you understand what compliant work should look like.

Checking for Waterproofing Failures

Wet areas — showers, baths, and laundry floors — must be waterproofed to comply with NZ Building Code clause E3 (Internal Moisture). Signs of waterproofing failure include:

• Grout or silicone that is cracked, missing, or discoloured around shower bases and wall junctions
• Tiles that sound hollow when tapped (indicating the substrate has moved due to moisture)
• Damp or musty smells in adjacent rooms or cupboards

Poor waterproofing is one of the most common and costly defects found in NZ homes. MBIE Building Performance has guidance on wet area requirements worth reviewing.

A Quick Reference: Red Flags at a Glance

When to Call a Professional

If you spot any of the signs above, it's important to act promptly. All plumbing, drainlaying, and gasfitting repairs must be carried out by a licensed tradesperson — attempting to fix restricted work yourself is illegal and can make insurance claims invalid. A licensed plumber can also issue a Certificate of Compliance for completed work, which is important documentation for your property.

For a thorough assessment, consider engaging a qualified building inspector who can identify plumbing defects as part of a broader property inspection. You can find licensed building inspectors, plumbers, and other qualified tradespeople in your area on check with your local council or the relevant licensing board (PGDB or LBP register) for qualified tradespeople in your area.

Safety note: If you ever smell gas or suspect a gas leak, leave the building immediately, do not operate any switches, and call your gas retailer's emergency line or 111.

Sources & Further Reading

• Plumbers Gasfitters & Drainlayers Board – Licensing & Restricted Work
• MBIE Building Performance – NZ Building Code
• BRANZ – Building Research
• Licensed Building Practitioners – LBP Register
• Tenancy Services – Healthy Homes Standards
• WorkSafe NZ – Gas Safety