When water has been through a property, the instinct once it goes down is to get things working again. Power back on, appliances back on, life back to normal. For most things in a house that instinct is right and the worst case is that something does not work.
Gas is the exception, and it is the one worth being uncompromising about. A gas appliance that has been submerged can light, run and look completely normal while a safety control inside it no longer functions. There is no symptom telling you that has happened, which is precisely why it matters.
Do not relight a gas appliance that has been submerged. Water reaches the control valve, the flame sensor and the regulator, and the failure it causes is silent: the appliance can operate normally with a safety control that has stopped working. Have it turned off at the isolation point, and have it assessed and certified by a licensed gasfitter before it is used again.
- Turn the gas off at the appliance isolation point or the meter
- Do not relight, dry out, or test any submerged gas appliance yourself
- Do not assume a working appliance is a safe one
- Have it assessed by a licensed gasfitter before use
- Keep any compliance certificate issued afterwards
On this page
1. Why gas is different from everything else in the house
For most appliances, water damage produces an obvious result. It works or it does not. A washing machine that has been submerged either runs or it does not run, and either way you find out immediately.
A gas appliance has a second layer that the visible operation tells you nothing about: the safety controls. Those are the components that shut the gas off when something is wrong, and they only ever do anything in the situation you hope never happens.
If water has compromised one of them, the appliance still lights, still heats and still behaves entirely normally. The only difference is that the thing which was supposed to protect you no longer will, and there is no way to know that by using it.
This is the single point of this guide. Normal operation proves the burner works. It proves nothing at all about the controls.
2. What the water actually reaches
- The control valve. The component that regulates and shuts off the gas supply to the burner.
- The flame sensor. The part that detects whether the burner is actually alight and shuts the gas off if it is not.
- The regulator. Which controls the pressure the appliance receives.
- Electronic controls and wiring. Which on a modern appliance are involved in the safety sequence, not just in convenience.
- Corrosion that develops afterwards. Water leaves, silt and salts do not, and deterioration can continue for months after everything looks dry.
That last one is why "it has been fine for a few weeks" is not reassurance. The damage does not have to be immediate to be real.
3. What to do, in order
- Turn the gas off at the appliance isolation point, or at the meter if that is not accessible.
- Leave it off. Do not relight it to see whether it works.
- Do not attempt to dry it out, take it apart, or test it.
- Arrange for a licensed gasfitter to assess it before it is used again.
- Expect that some appliances will be condemned rather than repaired, and that this is the correct outcome rather than an upsell.
- Keep the compliance certificate issued for any work done, with the property records.
Point five is worth expanding, because it is where people push back. Manufacturers generally take a firm position on submerged appliances, and a gasfitter who tells you a unit cannot be certified is applying that position rather than inventing one.
Appliance been under water?
Leave it off and ring. We will assess it properly rather than guess.
4. It is not only the appliance
The appliance gets the attention because it is the thing you can see. Two other things are worth raising with whoever assesses it.
The installation itself: connections, isolation valves and any exposed pipework have also been through the water, and they are part of what has to be sound before anything is certified. Certifying an appliance on an installation that has not been checked achieves very little.
And the hot water system, which on a lot of properties is the gas appliance most likely to sit low and outside. It is worth asking about specifically rather than assuming it was included, because people tend to think of the cooktop and the heater and forget the unit on the external wall.
5. Worth knowing before the next time
- Know where your gas isolation valves are, at the appliances and at the meter, and know them well enough to find them in poor light.
- Know which appliances on the property are gas, including anything outside.
- Keep the compliance certificates for gas work together with the property papers, because they establish what state the installation was in.
- Photograph the meter area and the appliances while everything is normal. It costs nothing and it is useful later.
- If you smell gas at any time, leave, do not touch any switch, do not use a phone indoors, and ring from outside.
The first item on that list is the one that matters most in the moment. Being able to isolate gas quickly, without looking for a torch and a diagram, is worth five minutes of preparation on an ordinary day.
6. What we will not do
We will not certify a submerged appliance because somebody needs it working today. That is the whole point of certification and there is no version of this where bending it is a favour.
We will not tell you an appliance is fine because it lit. We will tell you what we assessed, what we found and what the position is, and where the honest answer is that a unit has to be replaced, we will say so and put it in writing.
And we will not give you an opinion on your insurance position, because it is not our field. What we can do is give you documentation of what we found and what we did, which is usually what an insurer actually wants.
- Do not relight a gas appliance that has been submerged, even if it seems to work.
- Water reaches the control valve, the flame sensor and the regulator.
- The failure is silent: the appliance runs normally with a safety control that does not.
- Corrosion can continue for months, so weeks of normal use proves nothing.
- Turn it off at the isolation point and have a licensed gasfitter assess it before use.
- The installation and any outdoor gas hot water unit need checking too, not just the cooktop.
Gas after water damage FAQs
It lit and it seems fine. Is it fine?
Normal operation tells you the burner works. It tells you nothing about the safety controls, which only act in a fault condition. That is exactly why a submerged appliance has to be assessed rather than trialled.
Can it be dried out and reused?
That is a decision for a licensed gasfitter and, in many cases, for the manufacturer's position on submerged units. It is not something to attempt yourself, and a unit being condemned is a legitimate outcome rather than an upsell.
What if only the bottom of the appliance got wet?
Still have it assessed. The components that matter are not always where people assume, and partial submersion is not a category that makes it safe by default.
It has been working for weeks. Surely it is fine now?
Not necessarily. Water leaves but silt and salts stay, and corrosion can develop over months inside components you cannot see. Time since the event is not evidence of safety.
Does this apply to a gas hot water system outside?
Yes, and it is the one people most often forget, because it is outdoors and out of mind. Anything gas that has been in the water needs the same treatment as the cooktop inside.
What paperwork should I end up with?
A compliance certificate for any gas work carried out, and a clear written statement of what was assessed and what was found. Keep both with the property records. Anything about an insurance claim is a question for your insurer rather than for us.