Radiator Repair and Maintenance — Leaking, Cold, Bunged-up

Our Leeds-Bradford based plumbers can check, maintain and repair practically any make or type of radiator and fix most radiator problems, e.g.

Cold radiators
Cold radiators upstairs
Cold radiators at the end of the system (e.g. in extensions/conservatories)
Radiators that are cold at the top but hot at the bottom
Leaking radiators
Corroded radiators, e.g. that need power flushing
Leaking radiator pipes
Excessively hot radiators — loss of thermostatic control

Like many plumbing jobs, simple problems with cold radiators and leaking radiators can often be fixed by the knowledgeable DIY enthusiast. For the more difficult jobs affecting the pipework between radiators, or affecting the entire central heating system, you’ll probably want a qualified plumber.

But, whether you fancy ‘having a go’ yourself or would rather leave the task to a qualified plumber, it’s always worth trying to identify the potential causes of the problem and worth learning a bit about the potential solutions. If nothing else, you might save us both a bit of time and money, by helping us get to the solution as quickly as possible.

So, whether you plan to DIY, or to give our professional plumbers a call, the rest of this page details how to diagnose and potentially fix a range of common radiator problems, e.g.

Cold radiators
Leaking radiators
Corroded radiators

Cold Radiators

Most householders find out that they have radiator problems when they turn on their central heating for the first time after the end of summer.

Check the Heating Boiler Pipes

With the central heating on, first check that the pipes nearest the boiler are very hot to the touch.

If these pipes are cold, you'll probably have to call in professional plumbers like ourselves to service the system.

Check the Radiator Valve Pin

Modern radiators typically have a thermostatic valve on the inflow.

Set the thermostatic valve on every radiator to the maximum temperature.

If after a few minutes, the radiators remain cold, the first thing to try is cleaning the pin which connects the thermostat to the radiator.

Clean the Thermostat's Brass Pin

Every radiator valve has one screw at its lowest point, near to where the plastic touches the metal.

Unscrew that screw completely, until it is loose.

Hold the thermostatic valve tightly and try to pull it straight off, without bending anything at all.

Find the small brass pin sticking out of the pipe to the radiator.

Squirt the pin with WD40 and clean off any material, especially any material at the end where the pin enters the valve.

Squirt it again, then push the pin in. It's on a spring so it should return when you stop pushing.

Gently grasp the pin in a pair of pliers, and slowly pull the pin outwards. If you do accidentally pull the brass pin out completely you should be able to push it back in fairly easily.

Clean the entire pin with some more WD40 and clean cloth.

With the thermostatic valve removed, the radiator should now be getting hotter. If it's still cold, the chances are that the problem is more serious, or elsewhere. If you can't identify an alternative source of the problem, call a qualified plumber like ourselves.

Otherwise, if it isn't then the problem is more serious than a dirty thermostatic contact.

Push the pin in and out a few times until it moves freely and returns to the point where you originally grasped it with the pliers.

Give the pin one last squirt of WD40 — but don't wipe it off — then push the whole thermostatic valve back onto the pipe. Re-tighten the screw at the base of the valve.

Turn all your radiators down from maximum to your required temperature.

If they all at the correct temperature after a few minutes, you're done.

Bleed Semi-cold Radiators

If your radiators remain cold at the top but very hot at the bottom they probably have air caught inside them.

To remove this air: bleed the radiators.

Unscrew the small valve at the top of the radiator. Air should hiss out for a while, then water should come out. When it does, quickly screw the valve shut.

Faulty Thermostatic Valves

If your radiator was hot when you removed the thermostatic valve, but too hot or too cold — rather than the correct temparture — when you replaced it, you may want to replace the thermostatic valve itself.

You may also want to consider replacing the 'gland' — the part which the brass pin pokes out of — at the same time.

On many modern radiators — where the gland is sealed-off from the main part of the radiator — this is a relatively simple process of unscrewing the parts. Older radiators may need to be completely drained first, and the parts may need to be removed and replaced by a skilled plumber.

Leaking Radiators

Leaking radiators should be fixed as soon as possible. If not, the damage to flooring — carpets, laminates, etc — and floorboards could be a lot more serious and expensive than you might think.

Identify the Source of the Radiator Leak

Given the round and bendy nature of pipes, the drip may often be some distance from the actual source of the leak.

So before you consider replacing a valve or seal, the first priority is to clearly identify the true source of the radiator leak.

Carefully dry the entire area around the visible water.

Dab dry tissue paper around all the areas that you think the leak might be — this should reveal the true source fairly quickly.

Leaking from the Spindle?

Use a spanner to tighten the gland nut.

If that doesn't work, undo the nut then wind PTFE tape into the spindle.

Leaking from the Coupling to the pipe?

Again, this may simply need the coupling nut to be gently tightened.

If that doesn't work:

Drain the radiator
Undo the cap nut
Remove the fitting and replace the olive
Either:
- Smear the olive with silicone sealant, or;
- Wind some PFTE tap around the olive
Re-tighten the cap nut

Radiator Leak Caused by Corrosion?

Radiator corrosion is commonplace, but it rarely leads to a direct leak.

When it does, the chances are that you'll need a new radiator.

An emergency temporary repair may be possible with plastic resin filler, but we would recommend that this be done by a professional plumber, since you are going to need the replacement radiator fairly soon anyway.

Radiator Leak Caused by a Faulty Valve

In this case you will probably need to drain part, if not all of the system.

Ensure that the replacement valve is of the same type as the original. Since a different type may not align with the water pipe.

Unscrew the cap nuts connecting the valve to the water — pipe while holding the body of the valve with a wrench
Unscrew the cap nuts connecting the valve to the adapter at the end of the radiator
Semove the valve from the adapter
Remove the adapter itself from the radiator by unscrewing it
Clean the threads in the end of the radiator
Wrap PTFE tape round the threads of a new adapter
Screw the new adapter into the end of the radiator — tightening with a spanner
Slide the valve cap-nut and a new olive over the end of the pipe and fit the valve
Hold the valve with a wrench and align it with the adapter — just like you did when dismantling of the old valve
Tighten the cap nuts holding the valve to the adapter
Tighten the cap nuts holding the valve to the water pipe
Refill the system with water
Carefully check the fitting for leaks — using the tissue paper method
If necessary, tighten the cap nuts a little more
Re-bleed all the radiators — see above — to ensure that they properly re-fill

Power Flush Radiators

Over time radiators and pipes corrode — leaving deposits of sludge, rust, limescale and other debris in your central heating system.

If left, this debris will reduce the efficiency of a heating system by both disrupting the flow of water around the system and by reducing the transfer of heat from that water to the metal radiator surfaces.

In extreme cases a powerflush may be the best option for clearing this stuff out.

What is a Power Flush (Powerflush?)

A Powerflush involves little more than pumping a mixture of water and cleaning chemicals around your central heating system — at high speed, but low pressure — so that that debris and crusts are detached, broken down and flushed away.

Do You Really Need A Power Flush (Powerflush)?

To tell the truth, it's quite difficult to tell without a full examination of the central heating system concerned, but the following paragraphs outline some of the cases when it is worth considering.

Signs to look for before considering a powerflush:

Cold patches on radiators — but not merely cold tops (see bleeding radiators, above)
Excessive noise from the boiler or the heating system pump
Discoloured water when you bleed the radiators — not just one radiator
Slow warming of the heating system
Cloudy water and associated limescale problems with your tap water

Many plumbers will recommend that you powerflush your central heating system before connecting a new boiler to an old heating system.

This is because new boilers are often condensing boilers and contaminants in the old heating system can damage the internal pipe work of the new boiler.

Critically, be sceptical about power flushing for problems when:

Only one radiator is affected — or a small subset of radiators
Faulty thermostats could be to blame
Small (barely detectable) leaks may be involved
Air locks in radiators may be the culprits
The system pump and/or boiler is dodgy

So check these things first.

The Power Flushing (Powerflushing) Process

A heating/gas engineer connects a powerful high flow/low pressure pump to the circulation pump in regular boiler systems or to the pump head in combination (combi) boilers – and injects cleansing chemicals into the flow.

The chemicals used in a powerflush include:

A sludge crust breaker and remover – to get rid of rust and sludge
A descaler – to break down limescale
A corrosion inhibitor – to stop further rusting from occurring

Power Flush: Costs and Time

An typical powerflush takes around 6 hours, but this is merely an estimate – badly corroded/encrusted heating systems will need more time, while others will need less.

The price varies with location and size of heating system, but can range from £350 up to £1200+ – sometimes the descaler isn’t even included in the original quote (so watch out).

Conclusions

Power flushing may be exactly the right solution if your problem is the systemic build up of corrosion and/or limescale debris – in a basically sound and efficient system.

It is quick, convenient, and reasonably cheap, but these things are irrelevant if:

The problem is not systemic and not corrosion-related
The old system is reaching the end of its natural life
An energy-efficient new system gives you greater savings