Signs of a Poor Install – Advice from a Leeds Engineer

Installing a new boiler should make your home warmer and your bills lower. But over the years working as a gas engineer in Leeds, I’ve seen plenty of rushed jobs and slap-it-in installs where the regs seemed to be treated more like suggestions than actual rules.

Most installs aren’t dangerous — but there’s a big difference between someone who just does the job, and someone who actually cares about the work they do. The sad truth is, I’ve seen plenty of cowboy installs and botched jobs where speed mattered more than safety or pride.

The problem is, many customers don’t know what a good install should look like — and that’s how corners get cut.
That doesn’t mean your boiler’s unsafe. No engineer (hopefully) is leaving behind something life-threatening.
But it is about the level of care given — and that plays a crucial role in your boiler’s lifespan, heating efficiency, reliability, and even the appearance of the job.

That last one — how neat it looks — isn’t just for show.
It’s a skill that only comes with years of experience and pride in our trade.

So if a young engineer turns up and the pipework isn’t pristine, it doesn’t mean he didn’t care — he might just lack experience.
Read this blog and you’ll know the difference: was your boiler installed by someone who cares, or someone who couldn’t give a damn?

It’s not about fancy gear or big talk — it’s about attention to detail, doing the little things right, and taking pride in the work.

You don’t need to be technical to spot it.
If you know what to look for, it’s obvious.

In this guide, I’ll show you the signs that tell you whether your installer cared — or just wanted to be in and out before tea.
If it all checks out — great.
If not, hopefully it’s still safe… but if you’re unsure, we’re always here for a second opinion.

1. Flue not finished properly

This one’s easy to spot — and it gives you a good idea of what the rest of the job might be like.

The flue is the pipe that gets rid of boiler fumes. On a proper install, it should run with a slight uphill slope back to the boiler. Outside, only the flue terminal (the end bit) should stick out of the wall — you shouldn’t see any of the white internal pipe. The hole around it should also be sealed up neatly.

But you’d be surprised how many bad installs we see where the flue sticks out too far, isn’t cut to size, or the wall hasn’t been sealed at all. An unsafe boiler installation can start with something as simple as a badly cut flue.
Even though some manufacturers allow a bit of the white pipe to show, there’s no excuse for not measuring and cutting it properly. If someone can’t be bothered to use a tape measure — or worse, doesn’t even know how — what does that say about the rest of the job?

A neat, flush-cut and sealed flue isn’t just about looks. Sealing the hole helps keep your home airtight, reduces draughts, and is just good practice in modern homes built to retain heat. It also shows the installer took care with the small stuff — which usually means they cared about the big stuff too.

What to check:

• Go outside and take a look. Is the flue cut clean and flush with the wall? Is the hole sealed all the way around? It shouldn’t feel loose.
  If the white pipe is sticking out, or there’s a visible gap around the flue, it’s worth having a Gas Safe engineer take a look.

2. Condensate Pipe Is Too Small or Not Insulated

Condensing boilers produce a constant trickle of waste water (called condensate) that needs to drain away. It’s slightly acidic and can freeze in cold weather — which is why the pipe needs to be big enough and properly insulated, especially if it runs outside.

But on rushed jobs, we often see the installer reusing the old overflow pipe — just 21 mm — instead of upgrading to the proper 32 mm waste pipe. And if it runs into a garage or outside with no insulation? Good luck in winter.

Frozen condensate pipes are one of the most common reasons boilers stop working during a cold snap. It’s avoidable — but only if the engineer takes the time to do it right.

Another reason it gets bodged: upgrading the pipe properly often means drilling a new hole through the wall with a core drill — and that takes time. If someone’s rushing the job or working to a tight price, corners get cut.

There’s also the issue of where the pipe terminates. Condensate is slightly acidic, so it should discharge into a waste pipe, external drain, or a proper soakaway (at least 500 mm from the wall).
If it’s just dangling out the wall, it can bleach your brickwork or damage paving over time.

What to check:

• Follow the white plastic pipe coming out of the bottom of the boiler
• Does it run outside?
• Is it 32 mm all the way through?
• Is it fully insulated along any external sections?
• Where does it terminate? Into a proper drain, waste pipe, or soakaway — or is it just dripping on the wall/floor?
• If it runs into a garage or has a long external run and it’s thin and uninsulated, it needs upgrading — otherwise your boiler might just give up working when you need it most: the coldest days of the year.

3. Green pipes, leaking joints, and flux mess

You don’t need to be an engineer to spot this one — just take a look under your boiler.

Sometimes pipework looks a bit rough because the installer’s new to the trade — maybe just out of college, still learning. Bit too much solder, a few messy joints. Fair enough — we all start somewhere.

But messy or not, if you’re seeing green streaks or white crusty residue, that’s usually flux — the acid paste used for soldering — left behind. It should always be wiped off after the joints are made. When it’s not, it’s another sign the job was rushed or corners were cut.

Problem is, that leftover flux doesn’t just look bad — over time it corrodes copper, and makes the install look neglected.

And if you see damp patches or actual drips, it’s worse — that means leaking joints. This isn’t wear and tear — it’s a clear sign of a botched boiler job. Loose compression fittings, dodgy soldering, whatever it is — slow leaks can eventually rot your floorboards or cause your boiler to lose pressure.

What to check:

•  Look under the boiler and around visible pipework
• Do you see green staining, crusty residue, or white powder on the joints?
• Any damp patches or signs of water loss?
• Or on the flip side… has someone polished the pipes? That’s love and care.

If yes — get it checked. It might just need cleaning, or the joints may need redoing properly. Either way, don’t ignore it.

4. No system clean and no filter fitted

This one’s a biggie — and it gets skipped far too often.
But it’s crucial for efficiency and your boiler’s lifespan.

When fitting a new boiler, the heating system should be properly cleaned out to remove sludge, rust, and debris. Then, a magnetic filter should be fitted on the return pipe to catch anything left behind.

But if the installer’s in a rush — or just doesn’t care — they’ll skip it. Maybe they give it a quick rinse, maybe nothing at all. Who knows? No flush, no inhibitor, no filter — just slap the boiler on and go.

We’ve seen jobs plenty of careless boiler installs where the system wasn’t flushed properly, no new filter was fitted, and they just left the old one in place from years ago. A few months later: cold radiators, kettling noises, or blocked plate heat exchangers. And if that old filter starts leaking during a service? Not ideal either.

What to check:

• Look under the boiler: is there a magnetic filter fitted on the return pipe?
• Ask your installer: did they powerflush, mains flush, or just done a quick chemical clean?
• Did they add an inhibitor? Show you any water samples or do an inhibitor test?

If they can’t tell you — or there’s no filter in sight — you’ve likely had the budget version of a boiler install. That can seriously shorten the boiler’s life, ruin efficiency, and even void the warranty.

(We go into more detail about flushing methods and system cleaning in another blog.)

5. No handover, no paperwork, no idea how it works

You’ve just spent thousands on a new boiler… and no one showed you how to use it?

Unfortunately, that’s more common than you’d think. A lot of installs are squeezed into a single day — by the time it’s wired up and tested, the fitter’s already knackered and ready to go home (or down the pub). Five minutes of boiler run-time, no explanation, no paperwork, no time for questions — just “it’s done, mate” and off they go.

Benchmark? Filled in like a guessing game.
Building Control certificate? Never shows up.
Help setting up the programmer, adjusting the heating, and topping up pressure? Forget it.
Warranty info? What warranty?

We hear it all the time:

“No one explained how to adjust the temperature or what it should be set at.”
“I didn’t know it needed servicing to keep the warranty.”
“The guy said it’s done, handed me nothing, and left.”

But proper handover isn’t just good manners — it’s part of the job. You should get:
– A Benchmark commissioning checklist properly filled in
– A Building Regs compliance certificate (usually posted later)
– Warranty registration (certificate usually posted or emailed by manufacturer)
– And a proper walkthrough of how your heating system works — controls, pressure, temps, the lot

What to check:

• Did you get the Benchmark logbook and user manuals?
• Has your compliance certificate arrived in the post?
• Do you know how to use the programmer, thermostat, and TRVs?
• Were you shown how to top up the pressure or when to book a service?
• Did the installer help set up your heating to suit your home?
• Do you know how to reset the boiler if any fault ocuring

If not, don’t wait until it breaks. Call your installer back — or get a trusted Gas Safe engineer to give it a proper once-over and walk you through it.

6. Oversized boiler, undersized gas pipe

This one’s common with online boiler quotes — the customer picks a boiler (usually too big), and an installer turns up just to fit what’s in the van.

No site survey. No proper sizing. No pipework check. Just whack in whatever’s been ordered online — job done.

But here’s the issue: bigger boilers need more gas.
If the installer hasn’t surveyed the job and checked the gas run beforehand, there’s usually no time or budget priced in to upgrade the pipe.
So they just squeeze it onto the existing line and leave it like that.
Result? Pressure drops too low, the boiler can’t deliver its rated output.
If a picky engineer turns up later, they might condemn the boiler, manufacturers may refuse warranty if the gas pipe is too small.

15mm pipe is a big alarm bell for combis — it might be okay on some small heat-only boilers depending on the run length, but not for combis.
And if you’re converting from a regular to a combi boiler, you’ll almost always need a gas pipe upgrade.

Oversizing is another issue — a boiler that’s too powerful for the property will short-cycle (keep turning on and off), which ruins efficiency and wears out parts faster.

What to check:

Only a Gas Safe engineer can test the gas pressure drop properly — but if your boiler was ordered online with no in-person site survey, it’s already a red flag.
Not just for the pipework — but for overall compatibility, safety checks, and building regulations too.

7. Radiators Not Balanced or Bled Properly

Once the new boiler’s in, a decent fitter will walk round, bleed the radiators to get rid of air (so they heat fully at the top), and balance the system so they all warm up together.

If they skip it, you’ll notice:

Tops of panels staying cold (air in the system)

Some radiators heating much quicker than others (system not balanced)

Balancing just means tweaking the lockshield valves so every radiator gets its fair share of hot water.
Bleeding releases the trapped air that stops radiators heating fully.
It’s not complicated, but it takes a bit of extra time — and because it’s one of the last jobs, it often gets skipped.

What to check:

• Any radiators cooler at the top than the bottom? (Needs bleeding)
• Some rads heating much slower than others? (Needs balancing)
• Did the installer actually check each radiator before they left?

If not, the system will still “work”, but not as well as it could — and that tells you plenty about how much care went into the job.

Bonus Tip: Deburring — This Is Next-Level Care

Want to know if someone really cares?

Ask your plumber or engineer about their deburring tool.

Most don’t even carry one — and if they do, it probably lives at the bottom of the bag gathering dust.

If they haven’t got one, it’s definitely not been done.
If they do… still no guarantee — but at least they were thinking about doing things right

Deburring isn’t some advanced trade secret — it’s a small step that shows care and attention to detail.
It smooths the inside and outside cut edge of copper pipe and helps prevent:

• pressure drop
• turbulence
• water noise
• damaged push-fit or press-fit seals

You’ll never see it — but if it’s been done, your system will run better.
It’s not about knowledge. It’s about care
Hopefully you’ve read this before your new boiler gets installed — and it helps you get the best out of your chosen installer.

What to do if something looks off

If your boiler’s already been fitted and any of these signs sound familiar, it doesn’t mean everything’s doomed — but it might be worth getting it checked.

We’re not here to scare you — just to help you understand what a proper install looks like. Most issues come down to rushing, cutting corners, or not following best practice.

Need a second opinion?
At A-Tech Installs, we offer honest advice and full boiler system checks across Leeds — whether we installed it or not.
No pressure, no hard sell — just a proper look from a local Gas Safe engineer who gives a toss.

or contact Gas safe is suspect illegal or dangerous installation 

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Attila Boruzs
A Tech Installs Ltd
Gas Safe Registered Boiler Installer — Leeds & West Yorkshire