Everything You Need to Know About TRV Valves

Let’s be honest, when you are picking out a stunning new radiator for your living room, the valves are usually an afterthought. You just want something that matches the colour of the radiator and does the job. But getting to grips with your valves, specifically Thermostatic Radiator Valves (TRVs), is one of the smartest things you can do for your home heating.

If you are upgrading your radiators, you have probably seen the term TRV plastered all over plumbing websites. While older, manual valves simply turn the water on or off like a tap, TRVs are significantly smarter. They can completely change how comfortable your home feels and how much you spend on your gas bills.

Here is the complete breakdown of how they work, the different types available, and how to choose the right ones for your pipework.

What is a TRV and How Does it Work?

Think of a TRV as a mini thermostat for an individual radiator.

Inside the plastic or metal head of the valve, there is a small capsule filled with either liquid or wax. As the air in your room warms up, this material begins to expand. This expansion pushes down on a tiny metal pin, which slowly closes the valve and chokes off the flow of hot water from your boiler into the radiator.

When the room cools down again, the liquid or wax contracts. This lifts the pin back up, opens the valve, and lets the hot water rush back in. You simply turn the dial, usually numbered from 1 to 5, to set your ideal temperature for that specific space.

Liquid vs. Wax vs. Smart TRVs

Not all TRVs are created equal. When you are shopping, you will generally come across three main types:

• Wax TRVs: These are the older, traditional style. The wax takes a little while to expand and contract, meaning they are slightly slower to react to temperature changes in the room. They are usually the cheapest option.

• Liquid TRVs: These are the modern standard. The liquid capsule reacts much faster to temperature fluctuations than wax. This means your room stays at a more consistent temperature, making them highly recommended for most homes.

• Smart (Electronic) TRVs: These are the top tier. Instead of wax or liquid, they use battery powered electronic sensors and motors to open and close the valve. You can connect them to your Wi-Fi and control the exact temperature of every single room from an app on your phone.

The Main Benefits of Upgrading

If you are still using basic manual valves, upgrading to TRVs offers some serious advantages.

• Room-by-Room Control: This is the biggest selling point. You might want your living room to be a cosy 21 degrees but prefer your bedroom to be a crisper 18 degrees for sleeping. TRVs allow you to create distinct heating zones all over your house.

• Lower Heating Bills: Without TRVs, your boiler pumps exactly the same amount of heat into an empty spare bedroom as it does into your main living area. By turning the dial down to 1 or the frost protection setting in rooms you rarely use, you stop wasting gas and save money.

• Meeting Building Regulations: If you are having a completely new central heating system installed in the UK, current building regulations actually require you to have TRVs fitted to your radiators to improve energy efficiency.

Choosing the Right Shape for Your Pipes

This is where many people get stuck when buying valves online. You need to look at where your water pipes are coming from to buy the correct shape of TRV.

• Angled Valves: You need these if your pipes are coming out of the floor and connecting to the side of the radiator. The water has to turn a 90 degree angle to get into the radiator.

• Straight Valves: You need these if your pipes run along the skirting board and connect straight into the side of the radiator, or if your pipes come straight up out of the floor and connect underneath the radiator (like on a towel rail).

• Corner Valves: You need these if your pipes are coming out of the wall behind the radiator and connecting to the side. They look much neater than angled valves because the valve head points inwards parallel to the wall, rather than sticking out into the room where you might knock your ankle on it.

Where Should You NEVER Install a TRV?

While they are brilliant for most of the house, there are a couple of places where a TRV will cause you headaches.

The golden rule is that you should never put a TRV on a radiator in the same room as your main central heating wall thermostat.

If you do, the two thermostats will end up fighting each other. For example, if the TRV shuts off the radiator before the whole room reaches the temperature set on your wall thermostat, your boiler will just keep firing constantly to try and warm up a room that the TRV has blocked off. Always leave the radiator in your main thermostat room wide open with a manual valve.

It is also often recommended to avoid putting them in bathrooms. The sudden blast of heat from a shower can trick the TRV into thinking the room is warm enough, causing it to shut off your towel rail just when you need it to dry your towels.

A Quick Fix for a Common Problem

If you have an older TRV and you notice that the radiator is completely stone cold even when the heating is on and the dial is turned up to 5, do not panic.

Over the summer months when your heating is off, the little metal pin inside the valve can get stuck in the “closed” position. Simply unscrew the plastic head of the valve. You will see a small metal pin sticking up. Gently tap the side of the valve body with a spanner or push the pin down gently with a flat surface until it springs back up freely. Put the head back on, and the hot water should start flowing again.