Gemark Consultancy

The $20,000 Plumbing Problem No One Checks

Here’s the uncomfortable truth:

Most buyers will spend hours looking at
• kitchens
• bathrooms
• paint
• finishes

But almost no one checks what’s happening underground.

And that’s where the expensive problems live.

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What we keep seeing

Across multiple properties, the plumbing system is:

• Still working
• Not visibly failing
• Passing basic inspection

But underneath?

• Old clay or earthenware pipes still in service
• New fixtures connected to outdated drainage
• Mixed pipe materials joined underground
• Stormwater discharging into soil instead of proper connection

All functioning…

Until they don’t.



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Why this matters

Because when these systems fail, it’s not a small fix.

It usually means:

• Excavation through driveways or slabs
• Full drainage replacement or relining
• Stormwater redesign
• Unexpected costs that blow past your buffer

And none of that shows up in a standard walkthrough.

⸻

The blind spot

Most inspections are visual.

They don’t assess:

• Subsurface drainage condition
• Stormwater capacity
• Groundwater behaviour



So buyers assume:

“If it’s working, it’s fine.”

That assumption is where people get caught.

⸻

The takeaway

A property can be:

✔ Structurally sound
✔ Clean and well presented
✔ Fully functional

…and still carry hidden plumbing risk underground.

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GemArk Consultancy
We don’t just check if it works.
We assess how long it’s likely to keep working.

Ever read a Building & Pest report and seen this?

“Plumbing not tested.”
“Drainage not inspected.”
“Recommend licensed plumber.”
“Further investigation required.”

Over. And over. And over.

And you’re sitting there thinking…

So what did I actually just pay for?

To be clear — building inspectors have a defined scope.
They are not licensed plumbers.
They can’t pressure test.
They can’t CCTV inspect drains.
They can’t assess stormwater capacity.
They can’t confirm backflow compliance.
They can’t test heated water system safety valves.

That’s not criticism.
That’s regulation.

Under the NCC and AS/NZS 3500 series, plumbing systems have specific performance requirements — but most pre-purchase reports stop at “visual only.”

The problem?

Most major post-purchase costs are underground.

• Failed stormwater design
• Compromised clay sewer
• Mixed pipework from DIY renos
• Systems operating at capacity
• Non-compliant hot water installs

You don’t need another general overview.

You need trade-specific risk assessment.

That’s where GemArk steps in.

We don’t replace Building & Pest.
We fill the gap.

Plumbing. Drainage. Stormwater. Compliance.

Because “further investigation required”
shouldn’t be your surprise after settlement.

🚽 The Small Pipe in Your Yard That Protects Your House
There’s a plumbing requirement in Australian homes that most people don’t even know exists.

It’s called an Overflow Relief Gully (ORG).

Under AS/NZS 3500.2 – Sanitary plumbing and drainage, residential sanitary drainage systems connected to sewer are required to have a compliant overflow relief point.

What does that mean in plain English?

If your sewer blocks, wastewater must discharge outside the house — not through your internal floor wastes, showers or toilets.

That little grated fitting outside your bathroom wall?

It’s designed to flood your garden instead of your living room.

And here’s where it gets interesting.

We regularly see ORGs that:

• Have been paved over
• Sit too high after landscaping
• Are replaced with sealed caps
• Are positioned below internal floor level
• No longer comply after renovations

The system may still “work” day to day.

But during a blockage event, the lowest opening becomes the overflow point.

If that’s inside the house — that’s where sewage will surface.

This isn’t about non-compliance accusations.
Most of these homes were compliant when built.

The issue is how they behave over time as levels change and renovations occur.

It’s one of those standards that quietly protects you — until it can’t.

Before you renovate, landscape, pave or raise finished levels, check where your overflow relief point is and whether it still sits correctly relative to internal floor levels.

Because when a sewer blocks, gravity decides where it goes.

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Commentary provided by Gemark Consultancy. Based on AS/NZS 3500.2 requirements and consultant observations. This is not legal or compliance certification advice and does not guarantee defect discovery.

That $49 bidet spray from the hardware store?
It might not be compliant.

Under AS/NZS 3500.1, a hand-held bidet spray is classed as a high hazard cross-connection risk because the spray head can sit below the flood level of the toilet bowl.

If there’s a pressure drop in the main, contaminated water can siphon back into the drinking supply.

That’s why backflow protection is required under AS/NZS 2845.3.

Most DIY installs don’t include compliant backflow protection or licensed installation.

This isn’t about fear.
It’s about understanding the standard.

If you’re unsure whether yours is compliant, get it checked properly.

Protect the water coming in — not just the water going out.

Brisbane is building houses closer than ever.

And no one is talking about what that does to the plumbing.

When homes are packed this tight:
• Stormwater has nowhere to go
• Downpipes dump against footings
• Sewer lines run through impossible access zones
• Drainage is under-designed to hit price points

Then 3–5 years later?

Movement.
Cracking.
Rising damp.
Blocked drains.
Six-figure repair bills.

And the worst part?

Most building & pest inspections don’t scope the drainage properly.
They can’t — it’s outside their trade.

That’s exactly why we created GemArk.

We don’t just look at the house.
We assess how water moves around it.

Because in Queensland — water is the biggest structural threat to your property.

If you’re buying in Brisbane, especially in new estates…

Don’t skip the plumbing inspection.

It’s the cheapest insurance policy you’ll ever buy.

Most buyers think building & pest covers plumbing.

It doesn’t. And it’s not supposed to.

Building & pest inspectors assess:

✔ Structure
✔ Framing
✔ Visible moisture
✔ Termites
✔ Roofing

They are not licensed to assess hydraulic performance under the Plumbing Code of Australia or AS/NZS 3500.

That means they don’t assess:

• Drainage capacity under load
• Stormwater design & balcony overflows
• Subsoil & groundwater management
• Backflow device compliance
• Heated water temperature control risks

A sewer line can be “not blocked”
… and still be sagging.

A balcony can “look fine”
… and have no compliant overflow.

A stormwater system can “drain”
… and still discharge into soil illegally.

These systems usually fail after settlement.
That’s when excavation starts.

That’s why Gemark exists.

We don’t replace building & pest.
We fill the plumbing gap.

If you’re buying in SEQ or Northern NSW,
ask yourself:

Have I had the plumbing assessed — or just looked at?

— Gemark Consultancy

seqproperty

Every one of these roofs has plumbing underneath it.

From above, everything looks perfect.
Straight streets. Clean lines. New builds. Renovated homes.

But what you can’t see from this height is:

• Stormwater capacity
• Subsoil drainage
• Mixed old and new sewer lines
• Undersized downpipes
• Groundwater movement
• Systems operating close to design limits

Most properties aren’t failing.

They’re just functioning.

And functioning isn’t the same as low risk.

Gemark Consultancy works underneath the visible layer — assessing drainage, stormwater and plumbing systems before purchase, before handover, and before problems surface.

We don’t create drama.
We assess system behaviour over time.

If you’re buying in Brisbane or South East Queensland, understand what sits below the surface.

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Gemark Consultancy
Independent Plumbing Risk & Drainage Advisory
Brisbane | SEQ