Which one have you got now?
- No cylinder, no tanksA combi. The boiler is the only piece of kit, and the hot tap runs after a short pause while it fires.
- A cylinder, no tanks in the loftA system boiler with an unvented cylinder. The cylinder is usually white or grey metal with an expansion vessel near it, and the shower pressure is good.
- A cylinder and tanks in the loftA regular boiler, also called a conventional or heat-only boiler. The cylinder is often copper with a foam jacket, and the hot water pressure upstairs is lower.
Swapping like for like is the cheapest replacement, because the pipework stays where it is. Changing type is possible, and often worth it, but it is a bigger job.
Combi boilers
A combi heats the radiators and heats tap water on demand, so there is no stored hot water and nothing to run out. It takes up the least space and is the simplest to fit.
The limit is flow. A combi can only heat so much water per minute, so a second shower running at the same time drops the temperature of both. In a flat, a terrace or a house with one bathroom that is rarely a problem. With two bathrooms in use at breakfast time, it is.
A combi also depends on mains water pressure. Where the mains is weak, the hot water will be weak too, and a stored system does better.
System boilers
A system boiler heats the radiators and heats a cylinder of stored water. The cylinder is unvented, meaning it is fed straight from the mains at mains pressure, so two or three showers can run at once at full strength.
The trade-offs are space for the cylinder, the cost of the cylinder itself, and a small amount of heat lost from storing water. The cylinder has to be fitted by someone qualified for unvented systems and checked once a year, which Ian does as part of the service.
For larger family homes, and for anyone who wants a proper shower, this is usually the answer.
Regular boilers
A regular boiler heats the radiators and a vented cylinder that is fed from a cold water tank in the loft, with a smaller tank to top up the heating. The pressure at the taps comes from the height of the tank, which is why upstairs showers on these systems are often weak.
They suit older houses that already have the tanks and pipework, houses where the mains pressure is too low for a combi or an unvented cylinder, and homes with several bathrooms and an existing pumped shower. A like for like swap avoids disturbing the plumbing.
If the tanks and cylinder are old, converting to a system boiler at the same time gets rid of the loft tanks and gives mains pressure hot water. Ian will price both.
How Ian decides
How many bathrooms
And how many are used at the same time. This decides combi or stored more than anything else.
Mains pressure and flow
Measured at the kitchen tap. Weak mains rules out a combi and points to a stored system.
Space
Whether there is room for a cylinder, and where the flue can go.
What is there now
Like for like is cheapest. Ian will say when changing type is worth the extra.
Ian is a Worcester Bosch Accredited Installer and fits Worcester most often, with the extended warranty that accreditation brings. He fits other makes on request.
Questions
Combi, system or regular: which do I need?
Most homes with one bathroom suit a combi, which heats water as you use it and needs no cylinder or tanks. Two bathrooms in use at the same time usually means a system boiler with an unvented cylinder. A regular boiler with loft tanks is usually only fitted as a like for like swap in an older house. Ian will say which fits your house when he visits. The guide goes into more detail.
How long should a boiler last?
A well serviced gas boiler is commonly expected to last 10 to 15 years. Once repairs start costing a large share of a new boiler, or parts are no longer made for it, replacing it is usually the better spend.
What warranty comes with a new boiler?
Up to 12 years' manufacturer warranty when the boiler is serviced every year, depending on the make and model. Ian is a Worcester Bosch Accredited Installer, which brings the longest Worcester warranties. Other makes come with the manufacturer's standard warranty, and he'll tell you what that is when he quotes.
How much does a new combi boiler cost fitted?
Ian quotes after a visit, because the type of boiler, its output, whether it is moving and what has to change around it all move the price. The guide explains what moves the price and what a fair quote should include.