Heating guide

By Elegant Radiators · Heating advice · 5 min read

TRVs are one of the most popular valve choices in UK homes — but fitting one on a towel rail is a mistake that leads to damp towels, musty smells, and frustrated customers. Here’s exactly why, and what to fit instead.

1. How TRVs work and why that’s a problem

A thermostatic radiator valve (TRV) senses the air temperature in a room and throttles the flow of hot water accordingly. When the room reaches your desired temperature, the TRV closes stopping hot water from entering the radiator.

On a standard panel radiator, this is ideal. The room is warm, the radiator can rest, and you save energy. That’s exactly what TRVs are designed for.

The problem: A towel rail isn’t just heating a room. Its primary job is to keep your towels dry and warm. The moment a TRV cuts the flow, your towels stop drying — regardless of how wet they are.

In most UK bathrooms, the room temperature will satisfy a TRV quickly. Bathrooms are small, often well-insulated, and heated from multiple sources. The TRV can close within minutes of the boiler firing up long before your wet towels have had a chance to dry.

2. The hygiene risk: bacteria and damp towels

This isn’t just an inconvenience. Damp towels left at room temperature are a breeding ground for bacteria specifically species that thrive in the warm, humid air of a bathroom.

Studies have found that damp towels used more than once without drying properly can harbour millions of bacteria within 24–48 hours. That characteristic musty smell? It’s the waste products of microbial growth.

Key point: A towel rail fitted with a TRV isn’t doing its job. Towels won’t dry properly, and hygiene suffers as a result.

For a towel rail to function correctly, it needs to remain hot throughout the central heating cycle — not just until the bathroom air hits 18°C.

3. What valves should you use on a towel rail?

The correct approach is to allow the towel rail to run at full flow whenever the central heating is on. This is achieved with a simple pair of valves:

Manual angle valve (Flow in/out sides) — Set once during installation. Controls the flow on/off and allows isolation for maintenance.

This setup ensures the towel rail runs continuously with the CH, keeping towels warm and dry throughout the heating cycle without any temperature sensing getting in the way.

The correct valve pairing

Manual valves on both flow sides. Both sized to match your pipe centres (typically 15mm). Your plumber will set the valves during commissioning to balance the system correctly.

4. What about dual-fuel and electric towel rails?

If your towel rail is dual-fuel (central heating with an electric element) or fully electric, you have more flexibility:

When using the electric mode in the summer, you must close one of the valves. If you leave both open, the electric heat will escape out into your central heating pipes instead of warming your towels.

Electric towel rails are the ideal solution for summer months when your central heating isn’t running — you get warm, dry towels year-round without any compromise on hygiene.

5. Common questions answered

Can I fit a TRV on a towel rail if I turn it to its lowest setting?

Even on the lowest setting, a TRV will close when it senses enough ambient heat — which in a bathroom happens very quickly. Not recommended.

My plumber wants to fit a TRV — should I agree?

Many plumbers fit TRVs as standard across all radiators without stopping to consider the actual purpose of a towel rail. Politely ask for a manual valve instead and explain that you need the rail to run continuously alongside your central heating for drying purposes.

And if your plumber pushes back? We’re ready to back you up — because when you think about it, the logic is pretty clear: a thermostatic valve that shuts off heat when the room is warm enough is the last thing you want on something designed to dry towels after a warm shower.

Feel free to show them this article. We’re happy to be dragged into the debate.

Will running a towel rail without a TRV cost more to heat?

Marginally. Towel rails are small compared to panel radiators and have a relatively low heat output. The efficiency gain from fitting a TRV would be negligible — and far outweighed by the cost of repeatedly washing towels that haven’t properly dried.

Does this advice apply to all towel rails, including electric ones?

For central heating towel rails: yes, always use manual valves. For electric-only towel rails: valves don’t apply — you control them via a plug timer or wall switch. For dual-fuel models: fit manual valves on the plumbing side, and the electric element handles the rest.

What size valves do I need for a towel rail?

Most UK towel rails use 15mm compression or BSP fittings. Check your rail’s specification — the pipe centres (typically 150mm or 200mm) will determine which valve style fits your installation. When in doubt, measure your existing pipework before ordering.