Boiler advice and FAQs

Repeated pressure loss usually points to a leak somewhere in the system, a pressure relief valve that is letting by, or an expansion vessel that has lost its charge. Topping up hides the problem; an engineer should find the cause.

A small rise is normal as water expands. A big jump – towards 3 bar – usually means the expansion vessel needs attention or the filling loop is letting water in.

Usually limescale or sludge restricting the flow of water through the heat exchanger, so water overheats in places. It should be checked, as it can shorten the life of the boiler.

Known as short cycling. Causes include an oversized boiler, poor circulation, a faulty thermostat or incorrect settings. It wastes energy and adds wear.

The code tells an engineer where to start looking. Note it down (or take a photo) and include it in your enquiry. Resetting more than once or twice without fixing the cause is not recommended.

It could be a gas supply issue, a faulty ignition electrode, a fan or pressure problem, or a frozen condensate pipe. Check other gas appliances and the gas meter, then call an engineer.

On combis, the diverter valve is a common cause. On systems with a cylinder, a stuck motorised valve, a pump or the controls may be to blame.

On a combi this often points to the diverter valve, a flow sensor or scale. On a cylinder system, the cylinder thermostat or a valve may be at fault.

Low mains flow, scale, a faulty flow sensor or a temperature setting can all cause hot water to come and go. An engineer can test the flow and the boiler.

Turn the boiler off, place a container underneath and call an engineer. Leaks often come from the pressure relief valve, a seal or a pump. Do not remove the casing.

Yes. It usually means fitting a new boiler elsewhere and changing the hot water arrangement. It is a bigger job than a simple swap.

Often, yes – the tanks and cylinder are removed. It suits many smaller homes but not those with several bathrooms or low mains pressure.

Only if a combi can keep up with your hot water use. If two showers often run at once, a system boiler may suit you better.

Usually, subject to where the flue, gas supply and condensate pipe can go. It adds to the cost.

Sometimes, if the loft is boarded, lit, safely accessible and has a fixed ladder. There are extra requirements, so it needs assessing.

Many can, but there are minimum clearances for servicing and ventilation, and the flue route must work.

A combi may not perform well. A system boiler with a cylinder, or other options, may be better. We test mains pressure and flow before recommending.

It depends on heat loss and hot water use, not just bedrooms. An oversized boiler wastes energy; an undersized one cannot keep up.

A cylinder fed directly from the mains, giving strong pressure at every tap without loft tanks. It needs specific installation and yearly checks.

Flues can often go out through a wall or roof, with extensions where needed, but must meet strict rules on distances from windows, doors and boundaries.