I've got a towel rail in my bathroom that is heated from my combi boiler. I'd like to fit a TRV to the towel rail. Is there any reason why I shouldn't do that? Should I buy a specific type of TRV, or would any TRV do the job?

1 Answer 1


Some engineers - in the uk - do not recommend fitting a TRV to the bathroom rad as a constant flow is required around the CH system for safety reasons. This is what I was told by a Gas Safe Engineer. The bathroom is a Wet Area so why do you need a TRV when all you want to do is keep it / get it dry. Unless others say so then no need to fit one. Two normal flow valves will suffice on a balanced system.

  • To expand further: Most bathroom radiators are "connected to the primary" - this means that their water supply is teed off before the three-way valve (i.e. the valve which controls whether the water heated by your boiler is sent to the hot water tank or the heating circuit). This is for two reasons: 1. When you turn your central heating off in the summer, you normally still want to dry towels; hence having the bathroom radiator come on with both the heating and the hot water is useful. [cont]
    – AndyT
    Oct 21, 2015 at 8:45
  • [cont] 2. After your boiler turns off, your pump keeps running for 5 minutes, to ensure that water doesn't sit in the boiler getting very hot. Depending on your system, the pumped water may go round the hot water tank (if the valve is one that stays open automatically), or if both hot water and heating valves are shut then the water needs somewhere to go - hence the bathroom radiator circuit is always open.
    – AndyT
    Oct 21, 2015 at 8:47

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