A running or blocked toilet is one of the most common household headaches in New Zealand — and the good news is that many causes are well within a confident DIYer's ability to fix. This guide walks you through diagnosing the problem, the tools you'll need, and the steps to sort it out safely.
Understanding the Problem First
Before grabbing your tools, it helps to know what type of issue you're dealing with:
- Running toilet – water continuously trickles or flows into the bowl, or the cistern never stops refilling. You'll often hear a faint hissing sound.
- Blocked toilet – water rises high in the bowl when flushed, drains slowly, or doesn't drain at all.
Both problems are different in cause and solution, so let's tackle them separately.
Fixing a Running Toilet
A running toilet can waste a surprising amount of water — and money on your water bill. The culprit is almost always inside the cistern (the tank at the back or above the bowl).
Step 1 – Open the Cistern Lid
Carefully lift off the cistern lid and set it aside. Inside you'll see the fill valve (inlet valve), the float, and the flush valve or flapper at the bottom.
Step 2 – Identify the Cause
Common causes of a running toilet include:
- Worn or warped flapper/flush valve seal – the rubber seal at the bottom of the cistern no longer seats properly, letting water leak into the bowl.
- Float set too high – water overflows into the overflow tube before the fill valve shuts off.
- Faulty fill valve – the valve itself is worn and won't shut off fully.
Step 3 – Adjust the Float
If water is running into the overflow tube, try bending the float arm downward slightly (on older ball-float systems) or adjusting the float clip on modern fill valves. The water level should sit roughly 25 mm below the top of the overflow tube.
Step 4 – Replace the Flapper or Flush Valve Seal
This is the most common fix. Turn off the water supply at the isolating valve (usually located on the wall or floor behind the toilet). Flush to empty the cistern. Unhook the old flapper, take it to your local Mitre 10 or Bunnings to match the size, and fit the new one. Turn the water back on and test.
Step 5 – Replace the Fill Valve
If adjusting the float doesn't help, the fill valve may need replacing. Replacement fill valves are readily available at hardware stores and are a straightforward DIY job — shut off the supply, disconnect the water line, unscrew the old valve, and fit the new one following the manufacturer's instructions.
Clearing a Blocked Toilet
A blocked toilet is unpleasant but usually fixable without calling anyone out.
Tools You'll Need
- Toilet plunger (the flanged/bell-shaped type, not a flat sink plunger)
- Toilet auger (also called a closet auger or snake) — available to hire or buy
- Rubber gloves and old towels
Step 1 – Plunge First
Place the plunger firmly over the drain hole in the bowl, ensuring a good seal. Push down slowly then pull up sharply — repeat 10–15 times with firm, rhythmic strokes. The suction and pressure usually dislodges the blockage. Flush to test.
Step 2 – Use a Toilet Auger
If plunging doesn't work, a toilet auger can reach further into the trap. Feed the cable into the bowl, crank the handle clockwise to work it through the blockage, then pull back to retrieve the obstruction. This handles most blockages caused by too much toilet paper or small objects.
Step 3 – Avoid Harsh Chemicals
Chemical drain cleaners are generally not recommended for toilet blockages — they can damage older porcelain and rubber components, and are hazardous to handle. WorkSafe NZ advises care when using any chemical products at home.
What's Causing Repeat Blockages?
If your toilet blocks regularly, the issue may be further down the drain line — tree roots, a collapsed pipe, or a build-up in the soil stack. This is a job for a professional with a drain camera.
NZ Building Code and Plumbing Regulations
In New Zealand, sanitary plumbing work is restricted work under the Plumbers, Gasfitters and Drainlayers Act 2006. This means any work that involves connecting or modifying pipes, drain lines, or sanitary fixtures must be carried out (or supervised) by a licensed tradesperson registered with the Plumbers, Gasfitters and Drainlayers Board (PGDB).
However, homeowners are permitted to carry out basic maintenance on their own home, such as:
- Replacing a flapper or flush valve seal
- Replacing a fill valve
- Unblocking a toilet with a plunger or auger
- Replacing a toilet seat
Always check with MBIE Building Performance if you're unsure whether your planned work crosses into restricted territory.
When to Call a Professional
Call a licensed plumber if:
- The blockage won't clear after plunging and augering
- You suspect a blocked or damaged drain line (gurgling from other fixtures is a tell-tale sign)
- The toilet is leaking at the base or from the cistern connections
- You need to remove and refit the toilet pan (this is restricted work)
- You're a landlord — under the Healthy Homes Standards, rental properties must have functional sanitary facilities at all times
You can find qualified, local plumbers and handymen in your area at tradedirectory.co.nz.
Safety Note
Always wear rubber gloves when working on a toilet. Turn off the water supply before opening the cistern for repairs. If you're unsure at any point, stop and get professional advice — a small repair done incorrectly can become a costly water damage claim.