We have radiators in all rooms but the ones in the bathrooms come on at different times to the rest of the house. This is particularly annoying when getting up at 6am and stepping into a freezing bathroom while the rads are on in other rooms.

Why does this happen and how can I fix it?

  • 2
    Electric, or hot water? Are there individual zone controls on each radiator? Multiple zones defined in the basement? More details are needed in order to determine the cause. Nov 8, 2011 at 13:43
  • Central gas condensing boiler for both heating and water for the whole house. All rads have individual thermostats except the one in the main bathroom. We don't have a basement - there is a single thermostat in the hall for the whole house.
    – williamsdb
    Nov 8, 2011 at 14:22
  • So there are no "timers" per se on the radiator system? Is the central thermostat programmable? Nov 8, 2011 at 14:25
  • No, no timers on the radiators. There is a central control panel that allows the heating and water to come on independently of each other and we have it set up this way but the thermostat itself is not programmable. You can only set it to a desired temperature.
    – williamsdb
    Nov 8, 2011 at 14:40
  • Does the one in the bathroom eventually get hot?
    – Tester101
    Nov 8, 2011 at 17:07

4 Answers 4


I think you need to balance the system; as water will always take the easier option.

So when the system first comes on most of the water will go to the radiator with the shortest pipe run, once the thermostat rad valves on that radiator shut down, then the water will find the next easier option.

So by turning down the “lockshield“ values (the value with a cover over it) on the radiator(s) that gets hot first and turning then up on the radiator that take longer to get hot, you can force the water to go to all of your radiators.


Based on the answers in comments it sounds like you simply need to turn the thermostat up in the bathroom, and make sure the hallway isn't so warm that it keeps the boiler from turning on.

  • Unfortunately I don't think it's that as there isn't a thermostat on the radiator in the main bathroom and all the other radiators are hot.
    – williamsdb
    Nov 8, 2011 at 15:14
  • Are you sure the valve for the bathroom radiator is fully open? If the boiler is hot, and other rads are hot there's water flow, and if there's no individual control for the bath, then it should be hot as long as it's "on". Nov 8, 2011 at 15:27

OP probably hails from the US, where things might be different. Here in the UK it's not uncommon for a bathroom radiator to be on the same circuit as the hot water tank - so it can function as a "towel rail" even when you're not running the central heating.

So - check the On/Off times for the HotWater side of the boiler programmer.


The answer is really simple as to why: the radiators in the bathrooms are plumbed in as part of the hot water circuit instead of the central heating circuit. So they come on when you have the timer set to heat your hot water. This is not uncommon.

You can fix it by getting someone in to re-plumb them in as part of the heating circuit or alter the times your hot water comes on.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.