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Why is my hot water not hot?

Combi boilers provide central heating and instant hot water from one single unit. So if your central heating is functioning perfectly, but there's no hot water coming out of your taps, it can seem a bit of a mystery.

Knowing a bit about how your boiler works may help to explain why your 'hot' water isn't hot.

Diverter valve

Given the multi-purpose nature of a combi boiler, the appliance needs a way of switching heat from your radiators to your hot water (and vice versa). The diverter valve is the key to controlling this action.

When you turn on the hot tap, the diverter valve opens to let water into the heat exchanger temporarily closing off the water used for your space heating. When you've used the hot water, the valve switches back to divert heat back to your radiators.

If your hot water is not working, it's possible that the diverter valve is either worn, faulty or just stuck in the 'radiator position', therefore not allowing the water to heat up in the first place.

It's also possible (especially on a cold day) that your boiler is suffering from a low flow-rate, and just needs more time to pass water through the heat exchanger. Try running the tap slower, and you may find the problem solved.

No central heating or hot water?

If your hot water isn't hot and your central heating isn't working either, it's worth carrying out some simple checks before you call out an engineer.

Firstly, make sure that the electrical power supply to your boiler hasn't been switched off by mistake. Assuming that's not the case, check that your thermostat is turned up, and that the clock settings on your boiler are accurate (if the clocks have just gone forward or back, you'll need to adjust them to get back on your regular heating programme). Check our video library for help.

If it's winter time, there's a possibility that frozen pipes are causing the trouble. A frozen boiler condensate pipe (which carries condensation away from your boiler) will generate an automatic shutdown of the boiler as a safety precaution.

We have two videos to help you thaw a frozen condensate pipe and to make sure it doesn't happen again.

If you're having any problems with a Baxi boiler, contact our customer support or find a registered installer who can help.

Information & advice

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