Gas Water Heater Slow to Heat Up? What to Check First
Last updated: 24 September 2026
Quick answer: An instantaneous gas water heater heats water as it flows through the unit instead of storing a tank of hot water, so if your gas water heater takes long to heat up, look at the pipework, the flow and the heater’s condition rather than an empty tank. A short delay is normal: the heater has to engage when you open the tap, and cooled water already sitting in the pipe has to clear before hot water arrives. But a wait of many minutes is not normal without an assessment. If the water never gets hot, alternates between hot and cold, or the delay has suddenly become much longer than before, arrange a professional check rather than keep testing it yourself.
First, identify what “slow” means in your home
Direct answer: Before calling anyone, record what actually happens at each hot-water outlet: does the heater turn on, does the water eventually get hot, does it stay hot while the tap is open, and is one outlet different from another? These observations help separate a simple pipe-distance issue from a flow, mixing, or heater fault β without you needing to open or adjust any gas equipment.
Compare a nearby tap (such as the kitchen) with a more distant one (such as a shower), and note whether the problem started right after installation or only appeared recently.
Why some wait is normal β and why a long one isn’t
Direct answer: Gas water heaters listed on our site as “Automatic, Instantaneous”, such as the Life by City Energy L10WFE, heat water as it flows rather than storing a tank of pre-heated water, so there’s a brief engagement moment each time a tap opens. Beyond that, any piped hot-water system β gas or electric β has to push the water already sitting in the pipe out before genuinely hot water reaches the tap. The more pipe between the heater and the outlet, the more water has to clear first, and that adds real time.
That explains a short wait, not a long one. If you’re seeing many minutes rather than a brief pause, something beyond pipe length β reduced flow, a mixer set too far toward cold, or a fault with the heater or its installation β is worth having checked.
Common possibilities to discuss with the installer
Direct answer: A nearby tap warming quickly while a distant shower takes far longer usually points to pipe length or routing; a heater that doesn’t start, lukewarm water with the mixer near fully hot, or temperature changes mid-shower point toward flow, mixing or the heater itself.
| What you observe | Possible area to check |
|---|---|
| A nearby hot tap warms up quickly, but a distant shower takes much longer | Pipe length, routing, and whether the correct hot-water line actually serves that shower. |
| The heater doesn’t appear to start when a tap opens | Water flow, gas supply status, any displayed fault indicator, or the heater’s operating conditions. |
| Water is only warm with the mixer turned close to fully hot | Mixer setting, temperature setting, incoming water conditions, or flow through the heater. |
| Temperature changes during a shower | Flow variation, simultaneous use at another outlet, mixer setting, or heater operation. |
| A delay that has suddenly become much worse than before | A change in flow, or a fault that should be inspected. |
These are possibilities to raise with a technician, not a remote diagnosis. For reference, the Life by City Energy L10WFE on our site lists a minimum flow rate of 2.2 L/min (per the product listing); that figure is specific to this model and shouldn’t be applied to a different heater.
Safe checks you can make before booking service
Direct answer: Note the heater’s brand and full model number, photograph any error code shown, and time how long hot water takes at two different outlets using your normal tap operation. This gives a technician something concrete to work from.
Also note whether the hot-water flow seemed weaker than usual, and whether another tap was running at the same time. If you have the user manual, check the ordinary user settings and troubleshooting steps β but avoid testing at very high temperature settings, because of scalding risk. Do not dismantle the heater, alter gas piping, bypass a safety feature, or attempt any gas repair yourself.
According to Singapore’s Energy Market Authority (EMA), “all piped gas appliances are required to be installed by a licensed worker” (EMA β Engaging licensed workers (gas), checked 20 Sep 2026). Treat repairs and alterations the same way: leave them to a licensed gas worker or the brand’s authorised service, not a general handyman or a DIY fix. That’s why we don’t give repair instructions here.
When should you call for help?
Direct answer: Request service if there’s no hot water at all, the heater shuts down repeatedly, an error code appears, the temperature is unstable, or the delay is clearly excessive β including a wait of many minutes.
When you contact the heater’s brand service provider or your installer, send the model number, a photo or short video of what’s happening, your timing at two outlets, and your installation date if you know it.
If you suspect a gas leak, do not try to fix it yourself: stop using the appliance, move away from the area, and call City Energy’s gas emergency hotline.
Where to go next
Direct answer: If you’re still deciding between a gas and an electric water heater, or which gas model suits your flat, two related guides cover that ground, and our team can assess the installation before you buy a replacement.
Read our gas vs electric water heater guide or our HDB gas water heater model guide, and browse our water heater range. If you’re replacing a heater, request an installation assessment with your current model number and a photo of the setup, or visit one of our 5 showrooms β call the branch first to check what’s on display.
FAQ
Is it normal for a gas water heater to take a while to get hot?
A short wait can be normal β the heater has to engage when the tap opens, and cooled water already in the pipe has to clear first. A wait of many minutes is not normal without an assessment, especially if it’s new or has suddenly got worse.
Why does my shower take longer to heat up than my kitchen tap?
This usually points to pipe length or routing β the further an outlet is from the heater, the more cooled water sits in the pipe and has to clear before hot water arrives. It can also mean the wrong hot-water line is serving that outlet, which is worth checking with an installer.
Can I fix a slow gas water heater myself?
No β do not dismantle the heater, alter gas piping, bypass a safety feature, or attempt a gas repair yourself. EMA states that all piped gas appliances are required to be installed by a licensed worker; leave repairs and alterations to a licensed gas worker or the brand’s authorised service too.
What should I record before calling for service?
The heater’s brand and model number, any error code shown, how long hot water takes at two different outlets using your normal tap operation, and whether another tap was running at the same time. This gives a technician a concrete starting point.
What’s a normal minimum flow rate for a gas water heater?
It varies by model β the Life by City Energy L10WFE on our site lists a minimum flow rate of 2.2 L/min per its product listing. That figure applies to this model only; check the specific listing for any other heater rather than assuming the same number.
What should I do if I smell gas near my water heater?
Do not try to fix it yourself. Stop using the appliance, move away from the area, and call City Energy’s gas emergency hotline.
Written by the Lighting Hub team. Last updated: 24 September 2026. Thinking of replacing your heater? Send us your current model number and a photo of the setup, or visit one of our 5 showrooms.
