9 Most Common Central Heating Pump Problems [And Pump Fixes]
You don’t have to be a plumber to identify central heating pump problems.
For example: Is your boiler making noise or leaking? Are your radiators cold even though you’ve just cleared them of all sludge build-up? Then a faulty central hot water pump may be the culprit.
A malfunctioning central heating pump can cause a range of problems with your entire heating system, including leaks, excessive noise, cold radiators, and more.
In this post, we’ll examine 9 of the most widespread heating pump issues, their causes, and optimal solutions.
If you’ve got an older boiler and you suspect it’s causing the problems you’re experiencing, you can check out boiler replacement quotes here. Otherwise, read on to find out more!
Table of Contents
What is a central heating pump?
A central heating pump in a central heating system takes hot water from the boiler and pumps it around the pipework in your property. This feeds the radiators, taps, towel rails and showers in your property.
If a central heating pump is not working, it can wreak havoc on your whole heating system. Often, a noisy central heating pump is the telltale sign that something is amiss.
Where is the pump located?
If you have a regular or system boiler, the central heating pump will be located next to the boiler, or in an airing cupboard.
If you’ve got a combi, on the other hand, you won’t need an external pump for domestic hot water or heating. The tap water already gets supplied at mains pressure, whilst combis typically have an integral pump to circulate water through your radiators.
We’re going to cover the most common heating pump problems and what can be done to fix them (or, how much central heating pumps cost to fix).
Central heating pump not working? Check these problems
Pump Problem 1: The pump is running, but it’s not pumping water around the system
If the central heating pump is running, then it should be vibrating slightly. The most likely cause of this problem is that the shaft or propeller on the pump is stuck.
On some occasions (especially when the motor is extremely hot), the pump’s motor is the problem. The pump will get warm, but it shouldn’t be hot to the touch.
This is particularly common on heating systems that have been left sitting for a while.
If a component on the pump is stuck and the pump is not circulating water, sometimes a gentle tap will free up any seized components.
If the seizure is happening on a regular basis, it’s a good sign the heating pump is on its way out and is likely to fail altogether.
A replacement pump is likely to cost £200-250 including installation. This is about what you’d expect to pay for a top-quality Grundfos central heating pump.
Check out our related article covering heating and boiler problems here.
Pump Problem 2: Pump is blocked full of dirt
As central heating systems age, dirt and metal particles from radiators and pipework break down and begin to flow through major components such as the heating pump. This dirt and grime builds up in major components in the boiler and causes them to fail. Luckily, pump blockages are quite easy to fix, as all it requires is a little bit of cleaning.
It’s common for the boiler pump to build up with dirt and then stop working correctly. When this happens, you’ll find your heating system heats up slowly, not to full temperature, or not at all.
The first point of call would be to hot flush the heating system with chemicals. This differs to a power flush as it doesn’t increase the pressure in the system. Increasing the pressure on old systems can weaken joints and components and cause leaks.
Once you’ve flushed the system and the pump is clean, a good preventative measure is to fit a magnetic system filter.
The magnetic system filter will catch a lot of the debris and help to prevent any future heating pump problems.
Always ask an engineer to check the heating pump when they come to do an annual boiler service.
Pump Problem 3: Airlocks & noisy central heating pumps
Another common heating pump problem is air locks. If air builds up in the pump, the pump will stop working correctly.
Many central heating pumps have a bleed screw that can be used to remove the air, and allow the pump to work again without replacing any internal parts.
If you hear noises coming from the central heating pump that doesn’t seem normal, airlocks are likely to be the problem. A lot of customers complain of a constant humming noise when airlocks are the problem.
Once you’ve located the pump on the boiler, look out for a small central heating pump bleed screw. Please bear in mind that the pump is full of water. Open the screw extremely slowly (less than a quarter of a turn will usually be enough) as there is likely to be a small amount of water leaking out of the pump once all the air is bled.
If this doesn’t fix the problem, it’s likely the pump noises have always been there. Some manufacturers supply anti vibration brackets which are easy to install with the right tools.
Pump Problem 4: Incorrect product installation
Not all heating pump problems can be blamed on the pump. If the system has never worked correctly, there’s a small chance that the central heating water pump may have been installed incorrectly. In a worst-case scenario, the original installer fitted the pump the wrong way.
This is extremely uncommon, but if the pump has been fitted incorrectly, then it needs to be switched around. Remember, you must drain the system before removing and turning the pump.
After refitting the pump, you’ll have to fill the system using the filling loop on the boiler. And remember, you’ll also need to bleed all the radiators and towel rails.
What kind of fuel does your boiler use?
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Pump Problem 5: Pump speed settings are incorrect
Newer pumps (such as the Grundfos central heating pump 15/60) will have speed and flow settings. They are extremely easy to adjust.
And usually they are between 1 and 3. 1 is the slowest water flow rate and 3 is the highest. On many properties, we have been to that have had radiators not getting hot, or the whole system not getting to temperature, the pump flow rate is the issue.
Locate the boiler pump. On top of the pump will be a switch. If this switch is set to 1 or 2, there’s a good chance that the flow rate is too low. You can flick the pump to 3, which is the most powerful setting.
It’s worth consulting a Gas Safe engineer first. The heat pump central heating may be set at 1 or 2 for a reason (such as a system doesn’t allow any further flow due to microbore pipes). Turning the setting up on a system that doesn’t require it could result in leaks or broken components in the boiler.
Pump Problem 6: Leaking pump
Boilers leak for a whole host of different reasons. One of the most common reasons that a boiler leaks is issues with the pump. This can be down to incorrect installation, the pump working itself loose, or even a blown seal due to incorrect pressure settings.
Check that the pump is secure. If it’s not, tightening it up can sometimes be enough to stop a water leak.
Check all the fittings on the pump. Corrosion maybe the cause of the water leak. If this is the case, you’ll need to fit a new central heating pump.
Finally, check the joint on the pump. If this is what is leaking, there’s a good chance that it’s the seal on the pump that is blown.
The two options here are to replace the seal, or replace the pump. If the pump is particularly old, a replacement is the best option. Read our guide on boiler installation costs, or go ahead and request a replacement here.
Pump Problem 7: No power
If the pump and boiler have no power, but your property has power, the likely cause is going to be the PCB unit. Hopefully, your boiler has power. If it’s just the pump that has no power (or won’t start up) there’s likely a wiring issue. On some occasions, small leaks can ruin the wiring on the pump.
First, start with the easy and obvious. Like other appliances pumps have fuses. Check that the fuse isn’t blown.
Also, check that are no leaks. If there isn’t, have a Gas Safe engineer come and check the wiring to the pump.
If the pump is old and corroded, there’s a good chance that other parts are going to fail and a replacement is likely in order.
Pump Problem 8: Pump won’t turn off
Most pump problems are related to pumps not working. However, on rare occasions we are called out to boilers where the pump constantly runs and won’t switch off. We’ve seen this to be a problem with the Baxi Solo range on a number of occasions.
A proper pump diagnostic needs to take place. In the past, we’ve seen pumps constantly running due to:
- Faulty PCBs (the circuit board on the boiler).
- Pump overrun stat is faulty.
- The mid position valve is sticking (this can be lubricated with WD40).
Pump Problem 9: Pump is worn out
Like any other mechanical device, a central heating pump can succumb to wear and tear associated with age. You can expect the pump to become worn out after about 15 years of service, but some can last as long as three decades.
If you’ve eliminated every other problem on this list, chances are that the pump is simply worn out and due for replacement.
If your central heating pump has lived past its useful service life, it’s simply time to get a new one. You can learn more about replacing central heating pump services, and the expenses you can expect, by clicking here.
Faulty Central Heating Pump: Conclusion
Whether you have a noisy radiator, a boiler making loud noise like running water, or you simply suspect your old central heating pump has gone, a fix is close to hand.
There are several telltale signs something has gone wrong, and we’ve covered 9 of the most likely problems with hot water pumps. Read our guide carefully for a solution, or else reach out to a professional to help if nothing is forthcoming.
If you have any questions relating to central heating pump problems, please leave a comment below and we’ll get back to you.