No hot (tap)water but heating working fine?

We've had our Tado for 2 months (6 smart radiator thermostats, a bridge and a wired smart thermostat). They have been connected with a Remeha Tzerra boiler and existing radiators without any issues.

Initially all worked fine and we were satisfied with all functionalities. However, ever since a month the system appears to be acting weird while the settings haven't been altered and do not appear to display any deviations. The tapwater used to get hot in an instant. Right now any of the following 4 scenarios occur: it takes minutes (>10) before the water turns warm, it stays lukewarm/cold, the taps only give warm water when there's multiple taps running, there is no hot water at all.

When I want an averagely warm shower I now need to run the tap of the bathroom sink simultaneously. That's the only way for getting a hot shower. And when it has reached it's temperature I cannot alter it. It then drops to ice cold, leading me to step out of the shower again and repeating the sink-trick.

I'd be really keen on finding out what's causing this as I've got a 8-months pregnant wife breathing in my neck. Has anyone experienced this before? Any idea what could cause this?

Thanks a lot!


  • I’m not familiar with your brand of boiler but it sounds like you have what we call a combi boiler in the UK. I’ve had this problem and it was not the boiler or the controls at fault.

    You probably have one or more mixer taps/showers where the hot and cold water are blended together before coming out of a single spout. If the mixer cartridge fails in one these taps it can lead to cold water entering the hot water pipework even when the tap is not in use.

    For instance let’s assume the mixer cartridge in the kitchen tap has failed. If you turn on the shower in the bathroom then cold water will flow from the main water supply into the kitchen tap, pass through the body of the tap and into the hot water pipework. The cold water then flows through the hot water pipe to the shower. The cold water is at the same pressure as the water coming out of the boiler, so little to no water is flowing through the boiler. Hence the lack of heated water.

    To identify which tap is at fault you need to shut off the water supply for each tap one at a time. Then turn on a different hot tap to see if you get hot water out. Hopefully the pipework connected to your taps have inline isolator valves that you can easily turn off. If it’s a shower is at fault then that’s usually the hardest to diagnose because the pipework normally does not have isolator valves.

    In the absence of isolator valves you may be able to detect the problem with your hand. Don’t run any water for a period of time so all the water in the pipes is at room temperature. At this time of year the incoming water supply from the street is usually quite cold. By holding onto the hot water pipe next to a tap while someone else turns on another hot tap you should be able to feel if cold water is flowing into the hot water pipework.

    I hope the above makes sense. It may not be your problem, but it’s definitely worth checking the mixer valves.

  • I used to get this regularly on my previous Baxi combi, it wasn't the thermostat at fault though but the diverter valve in the boiler has a membrane that eventually ruptures and needed replacing.

    Might be worth taking a look in that direction first
  • Vintageperson
    edited February 11
    Heating on ok but no hot water
  • hugbilly
    hugbilly ✭✭✭
    If it’s a combi boiler then the hot water is not controlled by the tado° system . . .
  • Not exactly true @hugbilly .....I have a Combi boiler and I have a tado Ext Kit plus 1 x Wireless Thermostat and 1 x Wireless Temperature Sensor.........I have a tado schedule with different water temperatures set for specific times of the day......when the hot tap is turned on the temperature of the hot water is set by my schedule.

    I have it set to 38°C during the day for normal hand/face washing and also to wash the odd cup etc.......I can then adjust the temperature via an Alexa voice command "Bath time" for bath/ doing this I don't overheat the hot water to a temperature that is not required.

  • hugbilly
    hugbilly ✭✭✭

    Ah, just shows I don't know much about combining boilers, never had one myself :^)