Most households on bottled gas think about the bottles exactly twice: when the hot water goes cold mid-shower, and when the bill for a delivery arrives.
There is a small piece of equipment between those two moments that decides how often either happens, and it is the part we most often find faulty.
How the setup actually works
Two cylinders, outside, and a changeover regulator between them.
The regulator does two jobs. It drops the gas pressure to what your appliances need, and it automatically switches supply from an empty cylinder to the full one. That is why you are supposed to be able to run out of gas without noticing: when one empties, the other takes over, and an indicator on the regulator tells you it has happened.
The system only works if somebody looks at that indicator and orders a bottle. If nobody does, the second cylinder empties too, and then everything stops at once.
The regulator is the part that fails
This is the practical message of this post.
At a property in Sunnynook the automatic changeover regulator was no longer working reliably and had to be replaced. We isolated the gas, removed the faulty regulator, fitted a new one, restored supply, leak tested every disturbed connection and confirmed it was operating correctly.
At another property the tenant reported a gas odour when the hot water first fired. The odour at ignition was normal for that unit and we explained that. But the leak check we ran anyway found a minor leak at the automatic changeover valve on the bottles — a genuine fault nobody had noticed, quite separate from the thing that had been reported.
A leaking or failing regulator does two things to you at once. It loses gas you have paid for, and it stops doing the automatic changeover, so you run out without warning.
”The bottles are emptying much faster than they used to”
Worth taking seriously, and worth testing before blaming anybody.
At a property in Hillcrest the report was a hissing sound at night and a smell of gas, with a 45 kg bottle having emptied unusually fast. We inspected the installation, carried out a bubble leak detection test and a gas pressure test, and demonstrated both to the customer on site. The installation tested sound with no leak found.
Because a bottle-side fault cannot be ruled out once the bottle is already empty, our recommendation was to take it up with the bottle supplier. That is the right order: prove your own installation is tight first, then you have something solid to raise with whoever delivers.
The other explanations, before you assume a fault: a change in usage, colder weather driving hot water and heating harder, a new appliance, or a pilot light on an older appliance burning continuously.
Why you notice it in the shower first
Because hot water is usually the biggest gas load in the house.
A continuous flow unit fires whenever you draw hot water, and it fires hard. So when supply is failing, marginal or interrupted, the shower is normally the first place it shows: water that goes lukewarm partway through, or never gets properly hot. If that happens and the cooktop still lights, do not assume the water heater has failed. Check the bottles first.
We attended a unit where the tenant reported no hot water, and the cause was simply that the gas fire had gone off, most commonly because the supply had been shut off at some point. The appliance was fine.
What to check yourself
Two minutes, outside, no tools.
- Look at the changeover indicator on the regulator. It tells you which cylinder is in use and whether one is empty.
- Check whether both valves are open. A closed valve on the full bottle defeats the whole arrangement.
- Look at the regulator and connections for corrosion, damp, or any sign of weeping.
- Listen, close to the bottles. A hiss is worth a phone call.
- Smell low, not high. LPG is heavier than air and sinks, so it pools near the ground rather than drifting up to head height.
If anything smells or hisses, close the cylinder valves, keep ignition sources away, and ring the gas emergency number for your supplier from outside the house.
Bottles emptying too fast, or a regulator you are not sure about? Send us a photo of the bottles and the regulator.
Common questions
Who owns the bottles and who owns the regulator?
Generally the cylinders belong to the gas supplier and you swap or refill them, while the regulator and the pipework from it into the house are part of the property’s installation. That matters when something fails: a cylinder fault goes to the supplier, and a regulator or pipework fault is a gasfitter. If the split is unclear, test the installation first, because that answer settles it either way.
How often should the regulator be replaced?
They are a wear item rather than permanent, and the usual advice is replacement on a schedule rather than on failure, because a failed changeover is discovered by running out of gas at the worst moment. If yours is old, corroded, or you cannot remember it ever being changed, it is a small job. We replaced one in Sunnynook for exactly that reason before it caused a problem.
Can I change a bottle myself?
Swapping a cylinder on the supplier’s connection is routine and people do it. What is worth doing carefully is closing the valve fully before disconnecting, checking the seal is present and in good condition, and leak testing the connection with soapy water afterwards rather than by smell. If the connection will not seal or the fitting looks damaged, stop and get it looked at rather than forcing it.
Should the bottles be outside?
Yes, and that is where almost all of them are. The standard’s own guidance is that cylinders should be located outside the building. Indoor cylinders feeding a cooktop are permitted under specific conditions, and those conditions are commonly breached in older work, which we cover in the bottled gas shut-off post.
My hot water went cold mid-shower. Is it the bottles or the unit?
Check the bottles first, because it is the cheaper possibility and it takes a minute. If both cylinders have gas and the valves are open, then it is worth looking at the unit, and if it is a continuous flow heater with a display, the error code is the fastest way to narrow it down. There is more on that in no hot water on a gas system.
Related reading
- Bottled gas: where the shut-off is, and what to check first
- No hot water on a gas system: storage, continuous flow, and which you have
- Gas work at home: what needs a certifying gasfitter, and what you should get on paper
- Gas fireplace keeps cutting out: what a service actually does
- Why do I smell gas when I turn on the shower?