Radiators Q&A: Everything You Need to Know

Table Of Contents:

• Why is my radiator leaking?

• How to change a radiator valve?

• How to stop a radiator leak at home?

• How to balance a radiator?

• Can you put a TV above a radiator?

• Which radiator to bleed first?

• Thermostatic radiator valve how does it work?

• Why is my radiator not working?

• How much does it cost to move a radiator?

• Can you bleed a radiator when the heating is on?

• Radiator making noise when heating on?

• Which side of the radiator is flow and return?

Why is my radiator leaking?

Radiator leaks are bothersome, but at the same time, it is a relief that most of the reasons for the leaks from radiators happen to be common cause. Knowing the type of leakage will help in relating its source and the reason behind this.

Common Causes of Radiator Leaks

• Corrosion and rust-during the passage of time, internal lining gets corroded by water and oxygen; hence tiny pinholes are formed at bottom or seams that cause drips.

• Damaged seals or gaskets-the joints between the pipes and the connection to the radiator itself may wear out, particularly the rubber seals.

• Loose or faulty valves-the bleed valve or thermostatic valve may be left loose or cracked.

• High pressure-If your heating system has been over-pressurized, water may be forced out through weak spots.

• Physical damage-such as accidental knocks, DIY accidents or even moving furniture can dent or crack a radiator. 

What You Can Do

• Find the source-dry the radiator and put tissue/kitchen roll around joints/valves to see where water appears.

• Tighten connections-this is usually enough to do a gentle turn with a spanner on the valve nut.

• Temporarily seal small leaks-Radiator leak sealants exist, but they are a short-term fix.

• Bleed and check pressure-The system should be checked as this relieves the stress if over-pressurized.

• Replacement of faulty parts-Leaking valves or gaskets can usually be replaced without replacing the whole radiator. 

• Professional Help-Once corrosion or crack has set in with the body of the radiator itself, then the only safe alternative is replacement. 

Tip: If the leak is from the body of the radiator itself (rather than from a valve or joint), it is usually not worth the effort to repair: replacing it is the long-term solution.

How to change a radiator valve?

Changing a radiator valve is not an easy task; however, accomplished DIYers can pull it off without complications, provided they take the little care and preparation needed. Old, leaking, or unwanted valves are being transformed, or perhaps you are putting in TRV, as part of an upgrade or simply rejuvenating the old fittings. Here is a nice guide for you that clearly takes you through the whole process.

Tools & Materials

• Adjustable wrenches and grips

• Towels and bucket (for spillage)

• PTFE tape or jointing compound

• Radiator bleed key

• New valve-manual or TRV

• Optional: decorators cap (to temporarily seal TRVs)

Step-by-step Guide

• Turn off the heating Letting the system cool completely should be the first step in starting.

• Isolate the radiator

• Close the manual/TRV valve by turning it clockwise.

• Close the makeshift valve on the opposite side (remember the number of turns for later resetting).

• Drain the radiator Place a bucket below the valve, loosen the nut connecting the valve to the radiator and let the water drain out. Open the bleed valve at the top to hasten the process.

• Take out the outdated valve. Carefully remove the valve by undoing the nuts on the piping side and the radiator side using a spanner and grips.

• Get the plumbing ready. To ensure a tight seal, clean the threads and wrap PTFE tape over the replacement valve's tailpiece.

• Install the replacement valve.Then, without overtightening the bolts, the replacement valve should be fastened to the piping and the radiator.

• Bleed and refill Allow the radiator to fill after closing the bleed valve and reopening both radiator valves. Bleed out any trapped air. 

• Check for leaks Turn back on your heating and check all joints. Tighten gently where required.

Pro tips: 

• Always keep plenty of towels handy; radiators could hold far more than you'd expect.

• If you're converting to a TRV, put them on the flow side of the radiator-check your system type.

• After you change the valves, check your boiler pressure-making sure to top up if required.

How to stop a radiator leak at home?

Although it creates havoc in your house, what you should know is that most of the time you will be able to repair it or at least slow it down until the permanent repair or replacement actually happens. Fixing technique is according to the source of leakage whether from the valves, joints, or the radiator body. The following is a simple but lucid guide that will assist you through it. 

Common leak spot:

• Valve gland nut This generally only requires tightening.

• Valve connection (pipe joint) PTFE tape

• Radiator body (corrosion/pinhole) Most often sealant or replacement required.

• Bleed valve Can leak if left closed improperly.

Step By Step: Stopping a Leak

• Switch Off the Heating: Allow the radiator to cool completely before working.

• Location: Identify source: Dry radiator, leave few tissues around joints/valves; check with where water appears.

• Gland Nut Tightening valve: If the leak is from the valve spindle nut, below the valve head.

• Seal Joint: In case leak originates from pipe connection, first switch off both valves. Only partially empty the radiator and tape PTFE on threads. Again reconnect joints. 

• Temporary patch for pinholes: Where rust alone causes leaks from the radiator body, add radiator sealant (used to be poured in water) or a two-component epoxy putty for temporary purposes. A radiator, however, will definitely require replacement as a long-term solution. 

• Restore Pressure and Bleed Up: After that Activation/Proinspections of boiler pressure and bleeding your radiator to extinguish trapped air. 

Pro-tips

• Always have a towel and a bucket handy because there is more water than you think in radiators.

• Your system is probably in need of a power flush since you have multiple leaking radiators or sludge.

• The replacement of a corroded radiator body is the only real, dependable long-term solution. 

In brief: Tighten the gland nut for small valve leaks; joints are resealed with PTFE tape for connection leaks; and sealant/putties are used only as a temporary measure on pinholes.

How to balance a radiator?

Once the lockshield valves are adjusted, the balance for the radiator will allow a more even flow of hot water across your dwelling. In certain instances if such balancing controls are absent, the radiators near the boiler are usually over-ridden , whereas the ones farther away remain lukewarm. Here’s a clear, step‑by‑step guide: 

Step-by-Step: How to Balance Radiators

• Turn off heating & let radiators cool You’ll be working with valves, so start with a cool system. 

• First, bleed the radiators to release any trapped air.

• Open the thermostatic/manual valve fully, and then open the lockshield valve (usually covered with a plastic cap) almost completely.

• Keep the heating off while you do this.

• Once ready, turn the heating back on and allow the system to run until nearly all radiators are hot.

• Then, check the order in which the radiators heat up (from closest to furthest from the boiler).

• First locate the radiators that need heating (closest to the boiler) and last heating (furthest from the boiler). Measure the differences in temperature ideally about 12-20 °C, between flow pipe (hot water in) and return pipe (water out). If possible, use a digital thermometer or thermal imaging. 

Lockshield valve adjustments 

• Start from the radiator closest to the boiler: close its lockshield valve almost fully, then open it slightly (about a quarter turn) 

• Move to the next radiator; for which you would also open its lockshield a little more. Continue until the last radiator reaches almost full opening. 

• This restricts the flow to “greedy” radiators, ensuring a more even distribution of hot water to those further from the boiler.

• Recheck temperatures, fine-tune all radiators in equal time to heat up. 

Key takeaway:

•  The most important thing in balancing water flow is system balancing, and not air bleeding. 

• Start with radiators closest to the boiler and work their way until the farthest. An even heating time across all radiators is the goal. Properly balanced systems save energy and keep every room comfortable.

Can you put a TV above a radiator?

Although it is possible to put a TV over the radiator, it is not in your best interest unless some precautions are taken. The major problem here is heat; radiators throw warm air upwards, and electronics really do not appreciate constant exposure to such rising heat. This can reduce the lifespan of your TV, discolour the screen, or even create electrical faults over time. 

A clear break-up is enumerated beneath: 

Health Hazards

• Heat damage: When exposed to continuously growing temperatures, internal components may distort, melt, or fail.

• Decreased heating efficiency: The TV may block airflow, which lowers your radiator's performance.

• Safety risks: The likelihood of electrical problems or fire increases with temperature.

Advice for a Safer Installation

• Keep distance: Keep the distance between the TV's bottom and the radiator's top at least 4 to 6 inches.

• The barrier Heat originating from the radiator can be diverted away from the TV by using a floating shelf or radiator cover as a barrier.

• Tilting wall mount: Tilting the TV slightly downwards subsequently directs heat away. 

• Ventilation: Check that the TV is not starving for air.

• Temperature watch: Touch the wall and the bottom of the TV from time to time - If it feels hot, it's a red flag.

Practical Alternatives

• If possible, mount the TV on an entirely different wall.

• If you're tight on space, a radiator cover that has a floating shelf on it would create a more comfortable buffer zone.

• A wall-mounted radiator design that puts heat sideways instead of straight up should also be considered. 

Bottom line: It’s possible if the heat buffer is well established. Otherwise, your TV and heating are both at risk.

Which radiator to bleed first?

It's an excellent question-since the sequence significantly matters for effectiveness. Here is the order advised to heat engineers:

Correct Order to Bleed Radiators

• Step 1: Turn Off Your Heating. Always start with the system switched off and cooled down to avoid burns.

• Step 2: Begin with the radiator which is last from the boiler.For example in two-storey homes, start on the ground floor with the radiator that is farthest from the boiler. Move on to radiators upstairs and start on the one farthest from the boiler.

• Step3: Work your way closer: Progressively bleed each radiator moving closer to the boiler, finishing with the one nearest to it.

The Effects of Bleeding on Boiler Pressure: After bleeding, your boiler's pressure may come down a couple of notches; top it up as necessary.

Quick Rules of the Thumb

• For a multi-storied house: Start from downstairs, the farthest from the boiler, then move up. 

• Single floor-house: Start on the one farthest from the boiler and move toward it. 

• Always finish with the radiators closest to the boiler.

Thermostatic radiator valve how does it work?

A thermostatic radiator valve (TRV) is a clever little gadget that allows you to give each radiator its own brain for individual control of the temperature in each room without fiddling with the boiler. Here's how it works:

The Mechanics

• It has two major parts.

• Valve body-in place on the pipe which feeds the hot water into the radiator.

• The element head- the dial labelled with numbers that you twist.

• Temperature sensing-Inside the head, there is a capsule which is filled with wax, liquid, or gas.

• As the room gets warmer, the capsule expands.

• This pushes a pin in the valve body, which gradually closes the valve to reduce the flow of hot water into the radiator.

• As the room cools, the capsule shrinks, causing the retracting pin to reopen the valve, letting more hot water in.

Result: A radiator automatically balances itself to keep the room more or less at the temperature you have set on the dial.

Meaning of the Numbers

• Namely: The numbers 0-6 do not correlate with radiator temperature, but with estimates of room temperatures within ranges.

• 0 = Off (frost protection mode may still allow a trickle if it’s very cold).

• 3 = 19-21°C approx (a comfortable living room setting).

• 5-6 = Maximum flow, useful for quick heating but less efficient.

Why are they useful?

• Energy efficiency: It saves energy by reducing heat loss in rooms that aren’t used.

• Comfort: Bedrooms can be cooler and living rooms warmer and doesn’t require constant boiler adjustments. 

• Zoning without rewiring: Like giving each room its own mini thermostat.

Think of a TRV as a self-adjusting tap for hot water into your radiator, guided by the air temperature in the room.

Why is my radiator not working?

• A radiator that is not heating is indeed frustrating, but fortunately, the reasons for this mostly remain common and are generally fixable without resorting to professional help. The most effective option would combine checking whether it is just the one radiator that is cold or whether several/all radiators are down. 

Common Causes (and What They Mean): 

If one radiator is cold:

• Air-blocked-Trapped air: top is cold/bottom is warm → bleed radiator.

• Sludge: Bottom is cold while the top is hot→ sludge (rust, dirt, debris) has settled inside, might need flushing. 

• Stick thermostatic radiator valve (TRV): the pin inside the valve can stick so that hot water will not flow. 

• Lockshield valve closed or wrongly set: very tight balancing valve not setting the water to circulate. 

If more than one radiator is cold:

• Boiler/heat pump problem: not generating or circulating hot water. 

• Low water pressure: check the boiler pressure gauge. If it reads below 1b, this may need topping up. 

• Pump failure or airlock in the pipes: either the circulation pump is not running, or air is blocking the flow. 

• Check if the central heating is off or the timer is mis-set: surprisingly common - do check the controls. 

Simple Quick Checks 

• Both radiator valves (TRV and lockshield) are open. 

• If it's cold on top, bleed it. 

• Check boiler pressure and top it up if low. 

• Turn the TRV all the way up and press the pin gently to check for a stuck pin.

• For multiple radiators, see if the boiler is on and the pump is running.

When to Call a Professional

• If sludge is thought to be present in the whole system (needs a power flush). 

• If the pump or boiler is suspected of being faulty; 

• If bleeding and checking of the valves has not helped

How much does it cost to move a radiator?

Moving a radiator can hardly be big work with costs varying greatly depending on the distance a radiator had to be moved, the type of radiator considered, and the condition of the existing pipework. An outline is given below: 

Typical Costs (UK averages)

• To move a central heating radiator: £150 – £400 (around £275 on average)

• For the moving of an electric radiator: Around £40 per hour (easier if it's plug-in; more if it is hardwired) 

• Lowering a radiator for some time: £100 – £150

• To install a new radiator instead of moving the existing radiator: £500 – £680 including valves and tails

• Making-good afterwards (plastering, decorating, joinery): £200 – £600 depending on wall/floor type

Factors Affecting Price

• Distance moved – A few inches are cheap; moving to the other wall or room costs more because of extra pipework. 

• Type of radiator – Larger or designer radiators may involve more labor. 

• Pipework access – If pipes are buried in walls/floors, chasing adds cost. 

• System condition – Older systems might need flushing or balancing after the move. 

• Trades required – A plasterer, decorator, or electrician (for electric radiators) may also be required.

Pro-Tip

If a bigger rebuild is planned, it is often cheaper to move radiators while other plumbing or decorating work is going on while trades are still on site.

Can you bleed a radiator when the heating is on?

Don't bleed a radiator while the heating is on. Reasons are as follows:

Why Not?

• Safety: When the bleed valve is opened, hot water and steam may spray out and cause burns.

• Air won’t escape properly:  When the system is hot, there will be pressure, and there may be cases when not all of the trapped air is released.

• Shocks to the Boiler: Bleeding while the pump is running will draw in more air into the system and this will actually make matters worse.

At What Point Do You Bleed? 

• When the heating has been switched off, and the radiators have cooled down.

• Now, locate the bleed valve (normally at the top corner).

• In most cases, either a radiator key will be used or a screwdriver for newer valves, and you will slowly turn it anti-clockwise.

• You should hear a hissing sound as the trapped air escapes.

• Once the water trickles out, then firmly tighten the valve.

• After the bleeding process, check the boiler pressure and top it up if necessary.

Thumb Rule

• Heating ON → Just to check which radiators show cold spots.

• Heating OFF → When actually bleeding them.

Radiator making noise when heating on?

There is a huge communication between man and radiator noise during winters. Some noises may mean all sorts of things to the radiator owner regarding its functioning, which they may wish to know. Given below are common sounds heard from a radiator and their sources. 

Common Radiator Noises & Their Meanings

• Gurgling/bubbling → Trapped air in the system. Fix: Bleed the radiator to release the air. 

• Banging/knocking (water hammer) → Pipes expanding/contracting against walls under high pressure/flow rate. Fix: Check pipe clips or reduce pump speed or rebalance the system. 

• Whistling/hissing → This may often be a faulty or partly closed valve, or water is flowing too quickly. Fix: Adjust the thermostatic radiator valve(TRV) or lockshield valve. 

• Clicking/ticking → Metal has been expanding and contracting during heating up and cooling down. Fix: Usually harmless, but sound could be dampened by insulating or cushioning the pipes. 

• Dripping/running sound → Either air is moving through the system or sludge is restricting flow. Fix: Bleed the radiator, and if that doesn't work, flush the system.

Signs when you should take them seriously

• Such noises can also mean, perhaps namely; pump problems, sludge buildup or boiler pressure problems, louder, more persistent, and more invasive noises.

• Neglecting such radiator sounds is generally harmless but it can result in inefficiency and higher energy bills. 

Quick DIY Checklist:

• Bleed radiator (with heating off and cool).

• Check both valves are open and set properly.

• Check boiler pressure (should usually be 1-2 bar).

• Listen for noise from one radiator or whole system.

Which side of the radiator is flow and return?

Good question—because knowing which pipe is flowing and which is returning helps with diagnosing heating issues, fitting thermostatic radiator valves (TRVs), and balancing your system.

Flow vs. Return Explained

• Flow pipe → Carries hot water from the boiler into the radiator.

• Return pipe → Carries cooler water back to the boiler to be reheated.

How to Tell Which Side is Which

1. Turn on your heating and let the system run for a few minutes.

2. Feel both pipes connected to the radiator:

• The pipe that gets hot first is the flow.

• The pipe that warms up later (and is usually cooler) is the return

3. Check valve arrows: Some valves have small arrows stamped on them.

• Arrow into the radiator = flow.

• Arrow out of the radiator = return.

Does It Matter?

• On modern radiators with bi-directional TRVs, it often doesn’t matter which side is flow or return—they’ll work either way.

• When single-direction TRVs or older systems are connected incorrectly, it might result in:

  • The radiator is not heating up adequately.
  • Noisy valves that bang or whistle
  • Reduced efficiency

Quick Rule of Thumb

• Hot first = flow

• Cooler = return