Frequently Asked Questions

Horsham Plumbing & Heating Engineers

Common FAQ’s

How much does it cost to change a boiler?

It is not possible to give an accurate price for changing a boiler without carrying out a detailed survey of your existing heating installation. There are so many factors which come into play, such as whether the system needs to be upgraded in design terms for the new boiler, do controls need to be updated, pipework reconfigured, current building regulations, flue termination and so on.

It is always best to get a survey and estimate from a qualified and experienced heating engineer.


If I use a Gas Safe Registered engineer does this guarantee I will get a good job?

In short, the answer is no. You must use a Gas Safe Registered engineer for any and all gas work.
This just means the engineer is competent to work on gas and therefore safe. It does not reflect on his quality of work or the manner in which he goes about his work. It just means the gas work is safe.

To install a boiler means not only doing the gas work safely but it also means following the manufacturers installation instructions to ensure the boiler is installed correctly as the manufactured intended and that the system is configured for the boiler to operate properly.
As in all things, you need the right man for the job.

The same rules apply to an Oftec engineer who is registered to work on oil installations.

What is a Combi boiler?

The word combi is short for combination. In respect of a boiler it means a combination of producing central heating and domestic hot water.  With a combi boiler there is no need for a hot water storage tank as the boiler produces instantaneous hot water when a tap is turned on.

Generally speaking combi boilers are not suited for large household with several occupants and bathrooms as they will only serve one or two outlets simultaneously. They are suited to offices and where you have a large heating demand and small hot water requirement for toilets and kitchen.

What is a condensing boiler?

A condensing boiler is a high efficiency boiler (A rated). The term condensing is associated with the way  in which fuel is burnt. The maximum amount of heat is extracted to the point where the flue gasses cool to their dew point causing the water vapour in the combustion gasses to be released in the form of water droplets, ie; condensation.

All system, vented or combi boilers are available in condensing models.

Why do some of my radiators not heat up properly?

There are several reasons why radiators do not heat up properly. You first need to establish whether this is due to air in the radiator or a circulation problem.

Air in the Radiator.

When the heating system is on the top of the radiator will feel cold whilst the lower half is hot. The radiator just needs venting through the air vent at the top of one end of the radiator.

If the lower half is cold and the top half is hotter this is likely to be due to sludge partially blocking the water ways in the bottom central part of the radiator. This is quite common on long radiators.

Poor circulation.

The best way to check this is after the system has been on for ½ hour or more, check the flow and return pipes to and from the radiator. If the flow is hot and the return cold this would typically indicate a blockage or air lock in the return pipework. You can try shutting off all the hot radiators for a short period and see if the return pipe starts to heat up.

If it does then open all the closed radiators and wait ½ hour to see if it stays hot. If it does all well and good. If not then this could indicate a circulation problem due to undersized pump or pipework or just that the system needs balancing.


A rough guide to balancing would be to shut the Lockshield valves down on the hot rads by 50% and wait and see if circulation improves.


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Horsham Bathroom Installations – Horsham Plumbing