My boiler keeps losing pressure, what should I do?

Is your boiler making strange noises? Have you found yourself stuck with no hot water? Or has your heating suddenly stopped working? These may be signs that your boiler keeps losing pressure… but panic not. It is one of the most common faults our team of Gas Safety Engineers are called out to resolve. Many of our customers contact us as an emergency when they are in this situation for the first time because they simply don’t know what to look for, or how serious it is if their boiler keeps losing pressure.

A & L Services U.K. Ltd – Heating and Plumbing have provided expert plumbing and heating services in and around Stoke on Trent for decades, and here, we are going to share some of our knowledge and experience with you. 

You will learn a few reasons why your boiler keeps losing pressure; why it is so important to keep an eye on it if you notice your boiler pressure dropping; how you can help yourself by staying on top of your combi boiler pressure; and finally, why calling in the experts is the safest thing to do if your boiler keeps losing pressure even after you have followed our steps to repressurise your boiler, or if you think there is something more sinister.

What is boiler pressure?

When a boiler is installed, the engineer sets the boiler pressure correctly to ensure the heating and water systems are working efficiently and effectively. Boiler pressure is the balance of water and air within the sealed system. You can find the pressure reading quite simply by looking at the front of the boiler, near the main controls.

The boiler pressure gauge is usually a dial with numbers, and often green and red sections. To function normally, constant boiler water pressure is required, and should be within the green section or the needle showing between 1 – 1.5 bars on the dial.

No matter how old your boiler or full heating system is, it will lose water pressure over time. And it is quite normal to expect to repressurise your boiler (or top up the water pressure) at least once or twice per year. However, if you notice your boiler’s pressure gauge dropping repeatedly, staying consistently low, or a sudden drastic drop of pressure, there could be something more which will need investigating.

A & L Services can help you out if you are in any doubt, with our boiler service and boiler repair, to give you the comfort that you will not be left with cold water and no heating on those chilly evenings. If your boiler keeps losing pressure, we are the ones to call.

Possible reasons why your boiler keeps losing pressure

There could be numerous possible reasons as to why your boiler keeps losing pressure:

Pressure relief valve (PRV) discharge pipe or Expansion Vessel are faulty. There could be small drips coming from the PRV pipe, and this is the first area professional engineers will look for signs of a leak.

If it is leaking, do not try to block the leak. It is a safety valve and will need replacing. An expert will also check the expansion valve for any signs of damage or leaks at the same time, so it’s far safer to call us in for an inspection at this point.  

Leaks in the radiators, towel rails, radiator valves or pipes. Corrosion, rust or limescale build up can cause leaks. It is relatively easy to spot these leaks and is always worth checking all the radiator valves and joints, as it will be more cost effective if more than one needs replacing to do them all at the same time.

If your radiators are aged or beyond repair and need replacing, A & L Services can provide you with a free quotation as part of our wider plumbing services. Simply contact us to request a quote, and we will make sure your heating doesn’t let you down when you need it!

Boiler joints have become rusty and leaking where there is a weak point. As above, if you spot a leak where one joint has failed, do a thorough inspection, as there could be additional weak spots. A Gas Safe Engineer will need to solder the joint to seal it once again and balance the pressure back to normal. 

Automatic air vent is leaking. Air pockets can collect in your central heating system. This is the reason radiators need bleeding from time to time, to release the air pressure and bring back to the normal balance of air and water within the system. But there is also an auto air vent to help stabilise it. If this is leaking, then it could be the reason your boiler keeps losing pressure.

Pressure gauge isn’t working properly. This could be quite dangerous, especially if you continue to top up the pressure in your system. Monitor the pressure carefully, and if there are no visible leaks from anywhere else in the heating system, then you must contact an engineer to resolve as soon as possible.

If you are in any doubt about your boiler or central heating and hot water system, please do not hesitate to contact our friendly team of experts to book an appointment. They can instantly assess the fault and put it right for you efficiently and safely. 

Is low boiler pressure dangerous?

As I mentioned earlier, loss of boiler pressure is one of the most common faults we are called out for. It’s often nothing to be too concerned about and can be easily fixed by a check of all elements within the boiler and heating system and then repressurising. But if your boiler keeps losing pressure and you are having to do this frequently, then it’s likely there is a leak somewhere which needs fixing.

A loss of pressure when the heating is on indicates there could be a small leak. But if the boiler loses pressure when the heating is off, this could be a sign of a more serious leak. A gradual loss of pressure could simply be because your radiators have not been bled for some time.

If the boiler water pressure becomes too low, the safety mechanism will switch the boiler off to prevent overheating, so is not overly dangerous if the fault is found and rectified.

How to repressurise your boiler

Before you attempt to repressurise your boiler, you must refer to your specific manufacturer’s manual, and carefully follow instructions. Not all boilers are the same, and some require tools to access and remove panels. If this is the case for your boiler, you must call an engineer to do this, do not attempt it yourself.

If yours is a boiler which is safe to repressurise, that means allowing more water to enter the system from the water mains, via what is known as a ‘filling loop,’ the following steps are usually required:

  1. Switch off your boiler and allow it to cool.
  2. Find your filling loop (usually a silver flexi pipe). Ensure both ends of the filling loop are attached securely.
  3. Allow cold mains water into the system by opening both valves. You will hear the gushing sound as it flows through.
  4. The pressure gauge will increase to 1.5 on the scale.
  5. Close each valve, one first, then the other.
  6. Turn your boiler back on, and press the ‘reset’ button, if required.
  7. Undo both ends of the filling loop. As you remove the ends, watch for water spillage. Top tip: keep your filling loop in a safe place.

Baxi is one of the most well-known and preferred boiler providers, who show you in a video here how to repressurise your boiler if you are confident to do it yourself.

Conversely, if your boiler pressure rises above 2.75 bars, this indicates too much pressure. Bleeding your radiators may be a solution to releasing pressure from your boiler, but it may also indicate a fault within the boiler. It can be a timely and potentially dangerous task if you are not experienced, due to the high pressure and temperature of the water. See later why calling the experts could save you unnecessary concern.

What to do if your boiler keeps losing pressure after following our steps

If you are not so confident about following the steps above to repressurise your boiler, and want to ensure your system is thoroughly checked, any issues resolved, or if you have tried it on numerous occasions, and you still have the same problem where your boiler keeps losing pressure, then we would recommend arranging an appointment with one of our engineers.

Our team of professional, friendly Gas Safe Engineers here at A & L Services will clearly explain the problem, how we will rectify it, and will also spot any potential problems too before they start to cost, both financially and in terms of inconvenience.

As a family run business, with our engineers and plumbers based in Stoke on Trent, we know how important it is that you and your own family can rely on a local business like us to be there not only in your times of need, but also to maintain your plumbing, boiler, and central heating system on a regular basis, which we do as part of our boiler servicing offer. 

But, if you continue to notice your combi boiler keeps losing pressure, and can see no leaks, it could also be time to consider a replacement. If you are experiencing other faults and are not confident your boiler will last much longer, maybe reading this article from Which? five signs you need a new boiler will confirm your thoughts.

The cost of repeat, sometimes emergency, call outs and the inconvenience of losing hot water or heating, just when you need it most, will be far outweighed by a new boiler which you’ll once again be able to take for granted will never let you down.

We will respond to your queries if your boiler keeps losing pressure or provide you with a quote and install the most up to date and appropriate new boiler package (and anything in between!) And with decades of experience, we are your local plumbing and heating experts who pride ourselves in delivering an honest, reliable service, with an excellent 5 Star reputation across Stoke on Trent, Shropshire, Newcastle under Lyme, Staffordshire, West Midlands, and the surrounding areas.  Contact us today for a free quotation, and we guarantee 100% customer satisfaction for all your plumbing and heating needs.