Why Your Hot Water Runs Cold in Liss When Multiple Taps Are Used
If you live in Liss (GU35) or nearby Bordon, Alton, Liphook or Petersfield, you might notice your hot water feels luke-warm or even cold when two taps are on simultaneously. This frustrating issue often comes down to the output limits of your combi boiler and the flow rate demands of modern households.
How Combi Boiler Output Limits Affect Your Home
Combi boilers heat water directly from the mains, so they don’t require a separate hot water cylinder. While this space-saving design is perfect for many homes in Liss and Whitehill, it also means the boiler’s output rating (in kW) caps how much hot water you can run at once.
- Flow rate: A typical 24 kW combi might deliver around 9–10 litres per minute (l/min) of hot water. If two showers or taps demand 12 l/min in total, the boiler can only heat 10 l/min—leaving you with cooler water.
- Water pressure: Low incoming mains pressure in GU35 or GU32 areas will further reduce the flow rate your boiler sees, making it even harder to keep multiple outlets hot simultaneously.
- Temperature drop: The more water the boiler has to heat at once, the lower the temperature rise it can achieve. This is why the second tap often goes cold.
Liss Troubleshooting: Checking Your Boiler and Pipework
Before calling in a Gas Safe engineer, you can carry out some simple checks to see if it’s a flow-limit issue or something else:
- Test one outlet at a time: Run just your kitchen tap, then your shower. Note the temperature and flow rate. Repeat with both on to compare.
- Check incoming pressure: Look at the pressure gauge on your boiler. Ideally it should be between 1.0 and 1.5 bar cold. If it’s lower, topping up may help—refer to your manufacturer’s manual or ask a professional.
- Inspect filters and valves: Some combi boilers have magnetic or mesh filters on their inlet. A blocked filter can limit flow. Turn off the boiler, isolate the water, and clean the filter if you’re comfortable doing so.
- Look for pipework restrictions: In older homes around Haslemere or Hindhead, narrow pipe runs or scale buildup can choke flow. Flushing the system or repiping critical sections could make a big difference.
Optimising Hot Water Flow in a Busy Household
If you find that your combi boiler’s output is simply too low for your daily routine—especially in larger homes—you have several options:
- Upgrade to a higher-output combi boiler. A 30 kW–35 kW model can deliver 12–15 l/min, ideal for simultaneous showers and taps.
- Consider a system or regular boiler with a separate hot water cylinder if you need constant high volume for families.
- Install thermostatic flow regulators on shower heads to limit the amount of water each outlet draws, balancing your total demand.
- Use a hydrogen-combustion or condensing combi with improved heat exchanger design for a sharper temperature rise.
If you decide on a new boiler installation, our team will recommend the right size and model for your Liss home, ensuring you have enough hot water flow even on busy mornings.
When to Contact a Gas Safe Engineer
Some faults can mimic low output issues. You should call a professional if you notice:
- Fluctuating pressure readings on your boiler display.
- Strange noises or vibrations when heating water.
- No pilot light or electronic ignition failure.
- Repeated low-water-pressure lockouts.
Our certified Gas Safe engineers in Liss and surrounding GU34 regions can diagnose issues quickly and carry out any boiler servicing or repairs needed to restore reliable hot water.
Frequently Asked Questions
1. Why does my shower get cold when the washing machine is on?
Both appliances draw hot water simultaneously, pushing your combi boiler beyond its flow limit. Upgrading to a higher-output model or staggering usage can help.
2. Can I increase flow rate myself?
You can check and clean filters or adjust pressure, but altering internal settings or pipework should be done by a qualified engineer to comply with regulations.
3. Will a system boiler solve this issue?
System boilers work with a hot water cylinder, offering higher stored volume. They’re ideal if you need multiple outlets and lots of hot water back-to-back.
4. Do I need boiler cover if I upgrade?
Yes. Regular maintenance protects your investment. Explore our Boiler cover plans for peace of mind and priority breakdown response.
If you need help with your heating or boiler, our local engineers are here to help. Call us on (01420) 558993 or book online at embassygas.com/book.
Written by Embassy Gas — your local heating experts covering Bordon, Alton, Liphook, Farnham and surrounding areas.