What should my boiler pressure be?
1 to 1.5 bar on the gauge when the system is cool, for a Worcester Bosch boiler. Check your own manual.
Worcester Bosch says that when the heating system is cool, the gauge should read between 1 and 1.5 bar, usually in the green section. Below 0.5 bar means water has been lost and needs replacing. A reading of about 2.75 bar or more is too high. Other boilers may differ, so check your manual.
Check the gauge when the system is cool. If it reads below the range in your boiler's manual, the pressure is low. Add it to your snag list and report it to the builder. Ask to be shown how the heating and its controls work, and keep the manual.
Why do I keep having to top up my boiler pressure?
Some loss is normal. Worcester Bosch says the system will usually need topping up once or twice a year. If you are doing it much more often, contact your installer. In a new build, that means the builder.
Bleeding radiators can also lower the pressure, so check the gauge afterwards. Beyond that, a steady drop usually means water is escaping somewhere. Vaillant says leaks are most often found around radiator connections. Look for damp patches, stained paint on pipes and skirting, and marks on floors or ceilings.
Can a boiler lose pressure without a leak you can see?
Yes. Vaillant says that if you find no leaks, the cause may be a hidden leak on the system or a leak inside the boiler.
Take care
Don't take the boiler casing off. A Gas Safe registered engineer should look at it. In a new build, report it to the builder.
A trick we used a photo of the gauge each Sunday morning, before the heating came on. A few weeks of photos showed whether it was really dropping.
Why is my radiator cold at the top?
Air. Worcester Bosch says it is normal for air to build up over time. A radiator that is colder at the top than the bottom needs bleeding. If it is cold at the bottom and hot at the top, that can mean sludge, and the system may need cleaning.
To bleed one, turn the heating off and let the radiators cool. Open the bleed valve at the top with a radiator key, with a cloth underneath. Close it once water flows steadily, then check the boiler pressure.
If a radiator still won't heat properly, add it to your snag list. The NHQB lists radiators that don't heat properly or have trapped air as possible snags. Radiators can also need balancing, so each one gets its share of hot water. Vaillant, a boiler maker, recommends balancing a heating system at least when it is installed.
Thermostat, programmer and radiator valves
The programmer sets when the heating comes on. The room thermostat keeps the house at the temperature you choose. The valves on each radiator (TRVs) control each room. The Energy Saving Trust suggests the lowest comfortable temperature, for most people between 18°C and 21°C. Turning the thermostat up won't heat the house any faster.
In the first months, keep the temperature steady. The NHQB says sudden changes can make the home dry out too fast and increase shrinkage cracks. NHBC's guide says not to turn the heating up to its highest setting if you move in during winter.
How long should hot water take?
It depends on your system. If you have a hot water tank, it is heated on a timer, so hot water may only be ready at set times. The Energy Saving Trust says the tank's thermostat should be set to 60°C, hot enough to kill harmful bacteria and also hot enough to scald. If the heating and hot water system fails completely, the NHQB treats it as an emergency, not a snag.
Heat pumps and underfloor heating
Heat pumps work differently from boilers. The Energy Saving Trust says they run best kept on for long periods at a steady, lower temperature, with a lower setting when you are out or asleep. Your installer should leave an information pack and set the system up to run efficiently. Ask the builder to go through it with you.
For underfloor heating, the NHQB suggests a moderate temperature, adjusted gradually. Switching it on and off often is less effective.
Why is my new build so hot in summer?
New homes are designed to be energy-efficient and airtight. Since June 2022, new homes in England have had to meet a building regulation on overheating. It requires the home to limit unwanted heat from the sun in summer and to have an adequate way of getting rid of heat. A home whose building control application went in before then, and was started before June 2023, may not have been designed to it.
Owners must be given information on how the home is meant to stay cool. That includes where each part is, how to use it, and what time of day and year to use it. For example, shutters in the day and windows open only when it is cooler outside. If you didn't get this, ask for it. The guidance also says meeting it does not guarantee comfort. If a room is unbearable even when used as the builder explained, report it.