A bit of DIY plumbing can save you time and money — but only if you know what you’re doing. Here are the most common mistakes we see Melbourne homeowners make, and how to avoid turning a small fix into an expensive disaster.

1. Over-Tightening Connections

This is the number one DIY plumbing mistake. When people are worried about leaks, they crank fittings as tight as possible. The result? Cracked fittings, stripped threads, and broken pipes — which cause far worse leaks than what they were trying to prevent.

The fix: Tighten fittings until snug, then just a quarter turn more. If it leaks, tighten slightly — don’t force it. Plumbing fittings seal with correct technique, not brute force.

2. Using Chemical Drain Cleaners

Chemical drain cleaners are one of the worst things you can put in your pipes:

• They corrode old pipes, especially galvanised steel and cast iron
• They can damage PVC pipe joints over time
• They rarely clear serious blockages
• They create toxic fumes
• If they don’t work, you now have a pipe full of caustic chemicals for the plumber to deal with

Instead: Use a plunger, baking soda and vinegar, or a drain snake. For stubborn blockages, call a plumber who can use professional methods like water jetting.

3. Not Turning Off the Water First

It sounds obvious, but plenty of DIYers start disassembling plumbing without shutting off the water supply. The result is usually a flooded bathroom or kitchen and a panicked search for the shut-off valve.

The rule: Always turn off the water before working on any plumbing. Know where your isolation valves and main shut-off are before you start.

4. Mismatching Pipe Materials

Different pipe materials can react badly when connected directly:

• Copper to galvanised steel — Creates galvanic corrosion that eats through the joint
• Wrong glue on PVC — Using the wrong solvent cement for the pipe type causes weak joints that fail
• Mixed thread types — Metric and imperial threads don’t mate properly and will leak

The fix: Use proper transition fittings (dielectric unions for copper-to-steel). Always check that materials are compatible before connecting them.

5. Forgetting About Fall (Gradient)

Drain pipes rely on gravity. They need a consistent fall (slope) to carry water and waste to the sewer. Common mistakes include:

• Too little fall — Water pools and waste accumulates, causing blockages
• Too much fall — Water runs away too fast, leaving solids behind
• Sagging pipes — Over time, unsupported pipes can sag and create low points

The standard fall for drain pipes in Australia is 1 in 60 (approximately 1.65% grade). Getting this wrong causes ongoing drainage problems.

6. Ignoring Building Codes and Regulations

In Victoria, many plumbing tasks legally require a licensed plumber. DIY plumbing that doesn’t meet the Plumbing Code of Australia can:

• Fail inspection
• Void your home insurance
• Create liability issues if something goes wrong
• Cause problems when you sell your home
• Result in fines from the Victorian Building Authority

What you can do yourself: Change tap washers, replace showerheads, fix a running toilet cistern, clear simple drain blockages.

What needs a licensed plumber: Anything involving water supply connections, drainage modifications, gas work, hot water systems, backflow devices, or new fixture installations.

7. Not Testing After the Job

Many DIYers finish a repair, put their tools away, and walk away without properly testing. Then the leak shows up hours or days later — often causing more damage than the original problem.

Always test:

• Turn the water back on slowly and check every connection
• Run water through the system for several minutes
• Check underneath and behind fittings for drips
• Come back and check again an hour later
• Check again the next day

When to Call a Professional

There’s no shame in calling a plumber. It’s almost always cheaper than fixing a failed DIY job. Call a professional when:

• The job involves gas (never DIY gas work)
• You’re unsure about any step of the process
• The problem is bigger than you first thought
• You don’t have the right tools
• The work requires compliance certification
• Multiple attempts haven’t fixed the problem

Hankook Plumbing Is Here to Help

Whether you need a professional from the start or need someone to fix a DIY attempt that didn’t go to plan, Hankook Plumbing is here to help across Melbourne’s eastern suburbs.

Call 0407 756 172 — no judgement, just solutions.