Gas is the part of a house where the rules are strictest and the average homeowner has the least idea what they are. That is not a criticism. Nobody explains it until something goes wrong, a kitchen gets renovated, or a house goes on the market and the paperwork turns out to matter.
Here is what is worth knowing before you book anyone.
What you are probably here about
| What you have noticed | Usually means | What happens |
|---|---|---|
| Smell of gas | Could be a leak, could be normal combustion | Gas off, out of the house, ring it in. Then a pressure and leak test |
| Smell only when the hot water first fires | Often normal ignition on that type of unit | Confirmed by test, not by assumption |
| Bottles emptying faster than usual | A leak, or a bottle-side fault | Test the installation first, then talk to the supplier |
| Going to induction | Cap off the branch, or decommission the connection | Switching to induction |
| Buying or selling | Missing paperwork on past gas work | A gasfitter can test and certify what is there |
| Cooktop broken, parts unavailable | Replacement rather than repair | Cut-out size decides how easy that is |
| Califont not firing | Unit fault, gas supply, or water side | Diagnosis before parts |
What counts as gasfitting?
More than people expect. Running or altering a gas line is gasfitting. Connecting an appliance to that line is gasfitting. Disconnecting one and capping the pipe is gasfitting. Moving a hob two hundred millimetres along the same bench is gasfitting.
What is not gasfitting is swapping a bottle on a barbecue, or plugging in an appliance that was already connected and certified.
The line matters because gas work is legally restricted. It has to be done by a licensed person, and a certifying gasfitter is the one who can sign off the work at the end. The reason is simple enough: a bad joint in a water pipe makes a puddle, and a bad joint in a gas line does not.
The certificate, and why it is worth more than the job
When gasfitting work is done, you should end up with a gas safety certificate for it. Keep it. It is proof that the work was done by someone entitled to do it and that it was tested afterwards.
Two moments make people wish they had it. The first is selling the house, when a buyer’s builder asks who put the califont in and there is no answer. The second is a claim, when an insurer wants to know whether the appliance that caused the damage was legally installed.
If you have had gas work done and you were never given anything, that is a reasonable thing to ask about, and it is a reasonable thing to be suspicious about.
One thing that surprises people: we sometimes need something from you before the certificate can be issued. On a cooktop installation the certificate depends on the finished installation, not just our pipework, so we need a photograph of it complete, showing the wall surfaces behind the hob such as tiles or safety glass, and the rangehood above it. Those are part of what makes the installation compliant, and they usually go in after we leave. Send the photo and the certificate follows.
Where a property has older gas work with no paperwork behind it, a certifying gasfitter can test what is there and certify it. We quoted exactly that on a property with two separate LPG installations, both of which needed work before a certificate could be issued. It is a common position for a house that has changed hands a few times.
Taking gas out: capping off and decommissioning
A lot of our gas work now is removal rather than installation. Induction cooking has got good and cheap, tenants and buyers are less keen on gas, and plenty of people simply do not want the fixed line charge for one appliance.
Removing an appliance properly means disconnecting it, capping the line at a safe point, and testing that the cap holds. It does not mean pulling the hob out and squashing the pipe flat, which we do find.
If the gas is going entirely, you also want the supply properly disconnected rather than just unused, because a live capped line inside a wall is a thing future renovators discover the hard way. If it is only one appliance going and the rest stays, the remaining system gets tested as a system.
Bottled or reticulated, and why it changes the job
Reticulated gas is piped to the property and metered. Bottled LPG sits outside in forty five kilogram cylinders on a changeover regulator.
They are not interchangeable at the appliance. The two run at different pressures and appliances are built and jetted for one or the other. An appliance moved from a house on reticulated gas to a house on bottles needs converting, and an appliance that has not been converted will either not work properly or will not work safely.
The changeover valve is the part that fails. On a bottled installation the automatic changeover regulator switches supply from an empty cylinder to a full one, and it is the component we most often find leaking. It is a small part, it is quoted as a small job, and it is worth doing rather than living with. At Holmes Drive we quoted the replacement and the owner chose not to proceed at that stage, which is their call, but the fault does not improve on its own and it is going out through a regulator every day until it is replaced.
If your bottles are emptying faster than they used to and nothing about your usage has changed, get the installation tested before you assume it is the supplier, and get the supplier involved if it tests sound.
Bottle placement has its own requirements too. Cylinders need to sit outdoors, upright, clear of drains, windows and ignition sources, on a firm base. A cylinder tucked under the kitchen window because it is out of sight is a problem, not a solution.
Continuous flow water heaters
Most gas hot water in Auckland now is continuous flow, mounted on an outside wall. They are efficient and they do not run out, but they are appliances with electronics and a burner rather than a tank that sits there.
Two things keep them alive. Keep the flue and the intake clear, which means not building a deck around it or planting something that grows into it. And have it serviced rather than waiting for it to fail, because most of what kills them is scale and dust rather than age.
If yours is short-cycling, running lukewarm, or throwing an error code, get the code before you call. It saves a diagnostic visit.
When the appliance is too old to repair
Gas appliances outlive their spare parts, and this catches property owners out because the appliance still looks fine.
We attended a rental in Unsworth Heights for a faulty gas cooktop and found it was an older Smeg model that Smeg no longer supports with parts. Repair was not an option at any price, so the useful work was to establish the benchtop cut-out size and find a replacement that fits it, because a replacement with the same cut-out goes in without touching the benchtop and one with a different cut-out means benchtop alteration or a new benchtop. The manufacturer confirmed the existing cut-out, we put up two options that fit, and the property manager chose one.
If your cooktop has failed and it is more than about ten years old, ask about parts availability before paying anyone to diagnose it, and ask for the cut-out dimensions early.
If you smell gas
Do not look for the leak with a flame, and do not switch anything electrical on or off, including the light on the way out.
Turn the supply off at the meter or the bottle if you can reach it safely, open the windows and doors, get everyone outside, and call the gas emergency line for your supplier from outside the house. That number is on your bill and on the meter box.
We would much rather come out to a smell that turns out to be nothing. And in fairness, that is how most of these end.
Most gas smells we attend are not leaks, and the visit is still worth it. At a property in Massey a gas smell was reported. We carried out a gas pressure test and a leak detection test and confirmed there was no gas leak at all: the smell was combustion fumes from the appliance operating normally.
At Holmes Drive a tenant reported a gas odour when the hot water was first turned on. A brief odour at ignition is normal for that type of unit, and we explained that to them. But we ran the leak check anyway, and it found something else: a minor leak at the automatic changeover valve on the bottles. Two separate things, and only one of them was what anybody had noticed.
At Pupuke Road the report was a hissing sound at night and a smell. We inspected the installation and carried out a bubble leak detection test and a gas pressure test, and demonstrated both to the customer on site. The piping and installation tested sound with no leak. Since a 45kg bottle had emptied unusually fast, and a bottle-side fault cannot be ruled out once the bottle is empty, the recommendation was to take it up with the bottle supplier.
The pattern worth taking from those three: the test is the answer, not the nose. A smell that turns out to be normal ignition is a result. So is a sound installation with a suspect bottle. Both end a worry that would otherwise keep coming back.
Common questions
Can I install my own gas hob if I am handy?
No. Gasfitting is restricted work, and doing it yourself is both illegal and uninsurable. The connection is the part that looks easy and is not, and a joint that seems fine on the day can leak later.
Do I need a consent to remove gas from my house?
Removing an appliance and capping the line is gasfitting work rather than building work, so it is normally a certificate rather than a consent. Larger changes, or work that is part of a wider renovation under consent, get rolled into that consent.
My gas bill has a daily charge even though I barely use gas. Can I get rid of it?
That fixed charge is for the connection, not the gas. If you are only using it for one appliance, the sums often favour removing gas entirely and going electric, particularly when the appliance is due for replacement anyway. Ask us to price the disconnection before you decide.
Is gas hot water cheaper than a heat pump cylinder?
Usually not any more, on running cost. Continuous flow gas is cheaper to install and takes up less room, so it still wins where space is tight or a cylinder cannot fit. Where there is room, a heat pump cylinder normally runs cheaper.
How often should a gas appliance be serviced?
Follow what the manufacturer asks for, which is commonly every two years for a continuous flow unit and annually for gas heating. Rentals are the ones to keep on top of, because a property manager needs to be able to show it was maintained.
Related reading
- Somebody stole the hot water unit: what happens next
- Gas fireplace keeps cutting out: what a service actually does
- Your LPG bottles: running out, changeover regulators, and why they empty fast
- Commercial kitchen gas: certification, regulators, and used equipment
- Bottled gas: where the shut-off is, and what to check first
- Gas cooktop clearances and connections: what the standard requires
- No hot water on a gas system: storage, continuous flow, and which you have
- Switching from gas to induction: what happens to the gas line
- Ponsonby: taking out the gas cooktop for induction
- Hot water cylinder Q&A: the eight questions we get most
- Hot water cylinder replacement: what actually happens
- Why do I smell gas when I turn on the shower?
Thinking about taking the gas out, or need an appliance connected and certified? Call Nexus Plumbing or email [email protected]. We are certifying gasfitters, so the paperwork comes from us.