Glossary · Boilers and boiler types
What is a regular boiler (heat-only boiler)?
A regular boiler, also called a heat-only, conventional or open vent boiler, heats the water for radiators and for a separate hot water cylinder. It usually works with a cold water tank and a feed and expansion tank in the loft. It copes well with low mains pressure and with homes that need hot water at several taps.
Key points
- Regular, heat-only, conventional, traditional and open vent boiler are different names for the same type of boiler.
- A typical set-up has a cold water tank, a feed and expansion tank, a hot water cylinder and a pump.
- It works well where mains water pressure is low, because the pump, not mains pressure, drives the system.
- It is often the easiest swap for an older home, because the existing pipework and radiators can stay.
- You need room for the cylinder and the loft tanks, and exposed loft tanks can freeze.
How a regular boiler works
A regular boiler heats water but does not store it. The set-up around it does the storing. Worcester Bosch describes a regular boiler system as three parts: the boiler itself, which sends hot water to the central heating, a cold water tank that feeds the hot water tank, and a hot water tank that stores the heated water in bulk.[1]Worcester Bosch, Regular boilers
Baxi explains the loft tanks. One draws water from the mains and fills the hot water cylinder, which the boiler then heats. The other is the feed and expansion tank. It is usually smaller and keeps the water in the heating system at the right level. It also allows for expansion when the water gets hot.[2]Baxi, Heat only boilers A pump pushes the heated water around the radiators.[3]Ideal Heating, What is a heat only boiler?
This is an open vented system. For how it differs from a sealed one, see open-vented vs sealed heating systems and the entry on vented and unvented cylinders.
What a regular boiler system includes
| Part | Usual place | What it does |
|---|---|---|
| Boiler | Inside the home | Heats the water for the radiators and the cylinder |
| Cold water storage tank | Loft | Feeds the hot water cylinder |
| Feed and expansion tank | Loft | Keeps the heating water at the right level and takes up expansion |
| Hot water cylinder | Airing cupboard | Stores the hot water for taps and showers |
| Pump | Often the airing cupboard | Moves hot water around the radiators (see central heating pump) |
Baxi says a heat only boiler is a good option where mains water pressure is low, and for homes with more than one bathroom.[2]Baxi, Heat only boilers Worcester Bosch says it will deliver the same flow however many taps and showers are running.[1]Worcester Bosch, Regular boilers
Ideal Heating adds that a heat only boiler can also run on a sealed system, using an external pump and expansion vessel.[4]Ideal Heating, What are differences between a Combi, System and Heat boiler? It says these boilers are installed in many UK homes built before the 1970s.[3]Ideal Heating, What is a heat only boiler?
If a boiler is replaced or work is done on a system with a boiler, the current Approved Document L says a boiler interlock should be installed.[6]Ministry of Housing, Communities and Local Government, Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments Any work on the gas side must be done by a Gas Safe registered engineer.[7]Health and Safety Executive, Domestic gas: frequently asked questions
Example
Kofi has a 1960s house in Leeds with a cylinder in the airing cupboard and two tanks in the loft. The old boiler is failing. Worcester Bosch says a regular boiler is an easier, faster way to replace the heating in an older property because it uses existing pipework and keeps classic radiators.[1]Worcester Bosch, Regular boilers Baxi makes a similar point. If the old system may not cope with the higher water pressure of a combi or system boiler, replacing like for like may be the best option.[2]Baxi, Heat only boilers
Whether that is right for Kofi depends on the survey. If he wants the loft tanks gone, a system boiler is the other route. Our central heating pages cover both.
What people get wrong
People call any boiler with a cylinder a regular boiler. That is not quite right. A system boiler also feeds a cylinder. What marks out a regular boiler is the loft tanks and the open vented system, not the cylinder.
Ideal Heating says a heat only boiler can run on a sealed system as well as an open vented one, so the cylinder and tanks are what to look at.[4]Ideal Heating, What are differences between a Combi, System and Heat boiler? The other common error is to forget the downsides. Baxi lists the need for cylinder space, the wait while the cylinder heats and the fact that tanks in the loft could freeze.[5]Baxi, What are the different types of boilers? Ideal Heating adds that a heat only boiler can run out of hot water, and may be less efficient if you use little hot water because the cylinder heats more than you need.[3]Ideal Heating, What is a heat only boiler? Compare it side by side in system boiler vs regular boiler.
The bottom line
A regular boiler is the traditional type: a boiler plus loft tanks, a cylinder and a pump. It is good for low mains pressure, busy homes and straight swaps in older properties. It needs more space than other types and its loft tanks can freeze. A Gas Safe registered engineer must do the gas work.
Common questions
Is a regular boiler the same as a heat-only boiler?
Yes. Baxi says heat only boilers are also known as regular, traditional, conditional or open vent boilers. Worcester Bosch and Ideal Heating use the same names for the same type.
How do I know if I have a regular boiler?
Ideal Heating says that if your heating has a hot water cylinder and a pair of water tanks, usually in the loft, you have a heat only boiler. Baxi gives the same test of a small expansion tank and a larger cold water tank.
Does a regular boiler work with low water pressure?
Yes. Worcester Bosch and Baxi both say a regular boiler suits low mains water pressure, because the hot water comes from a stored cylinder fed by the loft tank instead of straight from the mains.
Can a regular boiler be used on a sealed system?
Yes. Ideal Heating says a heat only boiler can run on an open vented system with a loft tank, or on a sealed system with an added external pump and expansion vessel.
Sources
We cite the original source for every figure: government, regulators, standards bodies and manufacturers' own documents. Each one shows the date we last checked it.
- Worcester Bosch. Regular boilers. Checked 11 November 2026. ↩
- Baxi. Heat only boilers. Checked 11 November 2026. ↩
- Ideal Heating. What is a heat only boiler?. Checked 11 November 2026. ↩
- Ideal Heating. What are differences between a Combi, System and Heat boiler?. Checked 11 November 2026. ↩
- Baxi. What are the different types of boilers?. Checked 11 November 2026. ↩
- Ministry of Housing, Communities and Local Government. Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments. Checked 11 November 2026. ↩
- Health and Safety Executive. Domestic gas: frequently asked questions. Checked 11 November 2026. ↩