Boiler Faults and Breakdowns – North London



A sudden boiler breakdown is never good news, especially before the heating season. When you have to live without hot water and heating for days, it can be frustrating.


In this list here are few boiler fault problems and what cause the issue.


Low pressure in your boiler

To see if the boiler pressure is to low, the only thing you need to do is to check your boiler built-in pressure gauge. Your ideal boiler pressure has to be 1.2-1.5 bar when the heating system is cold. Below 1bar, your boiler stop working.

Also bear in mind that when you heat up the heating system your pressure it can be over 2 bar. This is because the water will expand when it’s heated.

Most of the time a boiler pressure problem can be caused by a leak. Usually, the leak will come through the radiator thermostatic or lock-shield valves. If you bleed out your radiators, you can also have a pressure drop in the heating system.

When a heating or gas engineer from MML Plumbing visit you to find a boiler fault, they first visually inspect the whole heating system and pipework. They looking for leaks on the pipework.

If the gas engineer won’t find the leak, that they need to take the boiler cover off and search the fault in the boiler.

The only person who can take off the boiler cover is a registered gas safe or heating engineer. All of our engineers are gas safe registered so you can have peace of mind that you are in good hand.

Book a boiler repair with MML Plumbing!


No power at the boiler

In this case, the first thing you need to do is to check the cooker or other appliances. You need to see if there are power supplies everywhere. Go to your fuse box and check if any switches have tripped.

If you still can’t find any issues, we recommend to call or make a booking with MML Plumbing ltd, we covering Barnet, and North London!


Leaking Boiler

Most of the leaks inside the boiler it is caused by an internal component fault, like a pump seal or pressure valve. If your pressure relief valve leaking, we are pretty sure that your system’s pressure is too high. High system pressure can be caused by a flat or damaged expansion vessel, you over pressurised the system by mistake or it can be the plate heat exchanger.

The plate heat exchanger can have a small leak inside between the main water and primary waterside. The main water could enter to the primary side and this will raise the pressure at the boiler.


If the leak comes from the pump, the seal is damaged and needs to be changed.

Whatever is the issue with your boiler or heating system we at MML Plumbing ltd can help you to get back the heating and hot water to your home.

Book a boiler repair!

You don’t have hot water or heating

A boiler fault like this for MML Plumbing is an everyday fault. I know for you it is frustrating a boiler breakdown when your boiler not giving any heat or hot water.

A boiler fault can be a source of a damaged system diaphragm, airlock, low pressure, faulty motorised valves or a broken thermostat.

For boiler faults, you need a gas safe registered engineer, who can inspect and test the components in your boiler. A gas engineer from MML Plumbing ltd needs to do various electrical and gas check at the boiler and also, at the gas meter to determine the real boiler faults.

If you have an airlock or a broken thermostat, it is very easy to check or repair. A boiler fault in the wiring it is more complicated and time-consuming.

Sometimes even you can identify for yourself a boiler fault, by checking the manufacturer instructions and find the boiler fault code what is on the boiler screen.

For boiler faults where we just have to repair the system, we can do that on the same day. If you need any special part than we have to contact the supplier to get the boiler parts for us.


Book a boiler repair with our gas engineer!


Faults at the radiators

This issue not always does a boiler fault, it only affecting the radiators. Cold spots at the radiator are caused by a heavy build-up sludge in your system or air what need to be bleed out. If you have a dirty heating system then the radiators heat up slowly, and the heat is distributed unevenly between the radiators. You can bleed out the radiators yourself.

If you don’t have a magnetic filter installed under the boiler the returned sludge from the radiators can block the main heat exchanger in the boiler and this can cause a boiler fault now.

Whatever is the issue in your boiler you can make a booking with MML Plumbing.


Boiler Condensate Pipe is frozen

These boiler faults are the most common problems in the UK between December and March. The responsibility for a condensate pipe is to transport the condensate water from the boiler to drain which can be internal or to outside. During the winter times, if your condensate pipe not lagged it can freeze, causing a blockage at the boiler, and makes the boiler not working till a gas engineer will fix this boiler fault. Firstly we need to melt the ice in the condensate pipe after we have to clean out the condensate trap and isolate the outside condensate pipe.


The room thermostat not turning on the boiler

It can be a few problems. One is that the clocks have gone backwards or forwards any your thermostat did not adjust this setting, you have to do this adjustment yourself.

If this is not working, you have to check the batteries at the thermostat. When you turn up the thermostat and the boiler is still not turning on, then you have a faulty thermostat.

If you have an unvented or an open vented system, the fault can also be found in the wiring box.

But to say 100% what is the real fault at your boiler without guessing, you can book a gas engineer at MML Plumbing, we can sort out any of your issues.

Boiler noises

It is totally normal if noise will come from the boiler when it’s starting to firing up. But if the boiler starts to make gurgling, whistling or banging noises, we recommend give a call to MML Plumbing and book a gas engineer.

The common problem for a noisy boiler can be air in the heating system, water pressure is to low, a faulty pump or limescale build-up making a kettling noise.

Book a gas engineer today


The Boiler pilot light turning off

Usually, older boilers need to have a permanent pilot light, this needs to stay lit all the time, this will light the larger burner. If the boiler fault is the light keeps going out, then the boiler thermocouple can be faulty, this can close the gas. Another common boiler fault can be deposit build-up.

If you feel comfortable you can try to investigate a few problems following the manufacturer instruction and reignite the pilot light.

Also, make sure all of the gas valves are turned on, and you have enough money on the prepayment gas meter.

Don’t do any other check. Call MML Plumbing ltd and a gas safe registered engineer will visit you who know exactly what steps need to be taken in this boiler faults.


Boiler breakdown

If you checked everything (you allowed too), we advised above and you still could not resolve the issues, then you need a gas engineer to visit you. If you leave these small issues to rise, this all can be grow to a serious boiler fault and complete breakdown. And from that moment, things start to get expensive.

If you do a yearly boiler service and checkups, you can avoid boiler faults and new boiler installations.


As you may know, an old boiler will break down more often and will cost more in the long run. So if your boiler is more than 15-20 years old, we advise you to install a new boiler.

With a new boiler, you can avoid boiler faults, you will get years of labour and parts warranty.



Quote your job today with MML PLUMBING! 


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