boiler replacements


Monday - friday
8.30AM - 5.30PM

about boiler replacements

what boiler is right for you?

Why not call us for a no obligation evaluation of your system, we will not just offer you a boiler, we will evaluate whether or not you will benefit from a boiler replacement and what if any other system changes may be required. If you have a system which is noisy, or frequently requires venting there is probably a fundamental problem with the system installation. We will discuss your needs and recommend a system that it right for you. We are qualified and registered to work on natural gas, LPG and oil and can also integrate solar thermal and heat pumps.

significant savings on hot water costs and the fact that hot water is delivered through your taps or shower at mains pressure. So you can enjoy powerful showering without the need for a pump.
Correct Installation is the single most important thing to ensure a reliable, long lasting boiler

We will ensure that the system is clean, that pipes, flues and vessels are correctly sized, that system components are correctly positioned to give your boiler and heating system the best chance of continued trouble free operation. We will ensure that the correct clearances are met and that best practice is followed.

As a consumer it is not always easy for you to be sure if your new boiler is being correctly installed and that proper, appropriate, system cleaning is being undertaken. Ensure that you ask your installer exactly what methods will be employed and how long things will take, you may be surprised how long it can take to undertake a new boiler installation correctly. If one installer is quoting a much shorter time than the others, it is unlikely that they are more efficient, it is far more likely that they are not allowing sufficient time to do a thorough job.

The importance of Compliance certificates

At the end of a new boiler/system installation we will carry out a full commissioning, we will take pressure, temperature and flow measurements, we will take flue gas samples and flue air pipe readings to make sure that your new boiler is up and running safely, efficiently and in accordance with manufacturer and industry standards.
Here at Smith’s the job is not finished until the paperwork is done!

We will leave completed ‘Benchmark’ certificates and all manuals with you at the end of the job. We will then register the guarantees for you and register the installation with Gas Safe/Oftec and the local council building control department. A certificate of building regulations compliance will be issued from Gas Safe/Oftec directly to you, but we will provide you with the serial number of that certificate.

If you do not have a building regulations compliance certificate, it will be very difficult to sell your house.

We are constantly surprised how often installations are not properly registered and this certificate is missing. It is imperative that you ensure that this will be supplied and it MUST be in the name of the installer, the practice of non-registered installers fitting gas appliances which are then ‘signed off’ by another installer is illegal!

boiler replacement Faq

In 2005 UK building regulations changed, meaning that high efficiency (condensing) boilers had to be installed in almost every case. Since that time standard efficiency boilers (non-condensing) have largely become obsolete, so in practical terms, yes everyone now must install a high efficiency (condensing) boiler.

When gas (or oil) is burned in a central heating boiler the largest waste product, which is discharged into the boiler flue and then into the atmosphere is water vapour. In older standard efficiency appliances the temperature of the flue gasses is generally between 150 and 200 degrees centigrade (higher for oil boilers). Due to these high temperatures the water vapour remains in suspension and disperses in the atmosphere.  The flue gas temperature from a modern, high efficiency, condensing boiler is closer to 50 degrees centigrade, meaning that the water vapour condenses before leaving the boiler. This large difference in flue gas temperature means that much more of the heat energy is transferred into the heating water and is one of the reasons why modern condensing boilers are so much more efficient than older, standard efficiency boilers.

The short answer to this is no, however this is a question which requires a more detailed answer.

Old traditional, central heating boilers were very simple appliances with little more than a burner, heat exchanger, (usually very large and made of cast iron), a thermostat and a gas valve, with such a simple appliance, there was very little to go wrong and so it is fair to say that these appliances were very reliable. They were also however very inefficient and therefore expensive to run and damaging to the environment, as well as being very large and often difficult to site in a modern domestic environment.

The increase in efficiency brought to us by modern condensing appliances can only be achieved by an increase in the complexity of the appliance. This increase in complexity obviously means that there is more opportunity for failure, however this does not mean that condensing boilers need be un-reliable.

One of the reasons we have chosen to work with Worcester Bosch for over fifteen years is their un-rivaled reliability and customer service, but even more important for the continued reliability of a new boiler is the quality of installation. It is essential to ensure that the system design and hydraulic layout is correct, it is important that the system is clean and that correct provision is made for disposal of the waste condensate from the boiler, particularly with consideration to ensuring that this waste condensate cannot freeze.

There is no right or wrong answer here, the type of heating system that is best for you will depend upon a number of issues here we will try to explain the different types of system and the advantages and disadvantages of each. It is of course essential that a central heating boiler is sized correctly for your central heating requirements, but probably the determining factor for the type of system chosen, will be how you plan to use your hot water. Essentially there are two main hot water system options from which to choose, but the second type is divided into two types;

This system, where the boiler instantaneously heats the water direct from the mains, is the most popular choice for most homeowners today, but is certainly not a solution that fits all requirements. If your hot water usage requires that multiple hot outlets be used simultaneously, then a combination boiler would almost certainly be the wrong choice, however if you have a single bathroom, but have a number of people all needing to use the shower/bath, one after another, then this is probably the perfect choice.

Hot water cylinder
This is best if you have two or more bathrooms and wish to use several hot outlets at once. This system can be divided into two types;

Vented hot water cylinder
This is the traditional system fitted in the UK, using a cold water storage cistern to feed a copper cylinder via gravity.

Mains fed Un-vented hot water cylinder (Often referred to as ‘Mega-Flo’)
This is modern replacement for the traditional hot water cylinder, it provides the benefit of stored hot water, which can supply multiple outlets simultaneously, but is fed directly from the in-coming mains supply with no storage tanks in the loft and no need for pumps for showers etc.
Again there is not a straightforward right or wrong answer here, a choice should only be made with due consideration to actual site conditions. Virtually all new properties in the UK will be fitted with mains fed, un-vented water systems, this is undoubtedly the best choice when starting from scratch. Often a mains fed system will still be the best choice for an existing property, but other factors must be considered when retro-fitting a mains fed system into existing properties.

Benefits of a mains fed system
  • Mains pressure water throughout the house
  • No need for shower pumps
  • Potable (drinking quality) water at all outlets
  • Dry loft (no storage systems, no ball valves to maintain)
  • Reduced risk of bacteria such as Legionella
The most important factor is the suitability of the mains water supply into the property. In a new build then a new plastic supply pipe with generally a minimum diameter of 25mm will be installed from the road (often 32mm, or greater for larger properties), this should ensure an adequate flow rate. In older properties, which were built with tank-fed gravity water systems, the mains supply pipe is often smaller diameter commonly ½” diameter, which may not be adequate to supply a suitable flow rate for a mains fed system. If mains water pressure is high, then a smaller main may adequate.

It is very important to take three measurements before deciding upon the type of water system to install;

  1. Static water pressure- This is pressure in your water main, when no water is being used.
  2. Dynamic water pressure- this is the pressure in the main when water is being drawn, it will invariably be lower than the static pressure, the greater the difference between these two pressures (static and dynamic), the smaller the supply pipe.
  3. Flow rate- this should be taken from a mains fed tap (a tank fed bath tap will give a meaningless reading). It is important to try to find an unrestricted tap if possible, often the outside tap will be best, this will show what kind of maximum flow the mains water supply can provide.
If you ask us to undertake a free of charge survey for you, we will take these measurements, if you are considering a mains-fed system.

The short answer to this is, we don’t know! It is impossible to guarantee this.
We can however make a sensible risk assessment of your system. Un-vented hot water systems are regulated to 3Bar pressure, with a 6 bar pressure relief valve. Standard copper pipe with soldered fittings should be capable of withstanding pressures way in excess of this, so provided they were installed correctly in the first place, they should be capable of taking the increased pressure.

Sealed central heating systems typically run at a working pressure of 1-2.5Bar, with a pressure relief valve setting of 3Bar, open vented central heating systems typically operate at a pressure of around 0.5Bar. Radiators are generally tested to a pressure of 10 Bar, so again theoretically existing heating systems, provided they are in good condition, should be perfectly capable of withstanding the moderate pressure increase associated with a sealed system, but we will be pleased to undertake a more detailed risk assessment of your existing system and recommend the most appropriate option.
In some instances, we will recommend continuing with an open vented system.

Even with very poor mains water pressures and flow rates, it is still possible to install high performance mains fed systems. We can achieve very high flow rates and higher pressures by installing mains water accumulators and where necessary a booster pump. There are many advantages of installing a mains water accumulator system, but is worth bearing in mind that there are two disadvantages. Firstly space, a mains water accumulator, by its mature is large, but it can be fitted anywhere, such as a garage, or loft space, secondly cost, accumulators and booster pumps add to the installation cost. The main benefit of an accumulator, is that you can guarantee the mains water flow rate and are not susceptible to fluctuations in the incoming supply, but a mains water accumulator is a completely sealed system giving potable water with no reduction of water quality. If you already have a mains fed water system and are unhappy with the flow rates, or water pressure talk to us about retro-fitting an accumulator system.

A combination boiler instantaneously heats incoming mains water up to a usable temperature using a heat exchanger inside the boiler without the need for a separate hot water cylinder.

  • Space saving- the combination boiler replaces the hot water cylinder, central heating header tank, cold water storage cistern, diverter, or motorised valves and separate heating pump.
  • Simplification of the heating installation, as all the components mentioned above are replaced by, or incorporated within, the boiler.
  • Lower running costs- the boiler only heats the water you actually draw rather than heating a full cylinder
  • Mains pressure, potable water all over house- no need for shower pumps etc. Drinking quality water from all taps
  • Dry loft-less risk of freezing
  • Un-limited hot water- no waiting for cylinder to re-heat, showers can be taken one after another without decline in hot water temperature.
  • No stored water in the event of water supply interruption
  • No Immersion heater back-up
  • Limited ability to supply multiple simultaneous demands- because combination boilers instantaneously heat water, it is not possible to supply several hot water outlets simultaneously, although larger combination boilers can supply two showers.
  • No hot water in the event of a power failure
  • Shower/ bath out let performance will be limited by the in-coming mains supply pressure and flow rates. (although we can use boosters and accumulators to control this is if necessary)

It is fair to say, that as with the modern car industry, most manufacturers make a fairly good reliable product, which, if installed and maintained correctly, should provide years of trouble free operation, but here are the reasons why we have decided to partner Worcester Bosch rather than any of the other makes of boiler .

    • Worcester Bosch are the widely regarded as the most reliable boiler brand by homeowners and installers alike and have been awarded Best Buy by consumer organization, ‘Which’, for the last nine years running.
    • 10 year guarantee on gas boilers, 7 year guarantee on oil boilers, when installed by Smiths Heating Services, provided a Worcester Bosch system filter is installed and the boiler is serviced annually.
    • Support when it is needed. Worcester Bosch’s customer service and technical helplines are open for longer hours than any other manufacturer, from 7.00am to 8.00pm Monday to Friday, all day Saturday and Sunday mornings, don’t take our word for it give them a call Tel: 033020123209559
    • Boilers are mechanical items, all modern boilers contain a fan, solenoid valves and printed circuit boards, many also contain pumps, valves and other moving parts. Regardless of how good a manufacturer’s quality control procedures are (and Bosch’s quality control is world leading), some components will fail, sometimes prematurely. In the unlikely event of a failure Worcester Bosch have by far the largest network of their own service engineers (over200), all of whom have fully stocked vans, which are re-stocked automatically overnight. Worcester Bosch also have an absolutely no quibble attitude to their guarantee, same cannot be said of many other manufacturers.
    • Proper manufacturer/Installer partnership We have been installing and maintaining Worcester Bosch boilers for approaching 20 years and have been Worcester Bosch accredited since 2003. Our close partnership means that we receive regular on-going training and support on Worcester Bosch products. Tom our youngest team member, has completed Worcester’s Apprentice program and was named Worcester Bosch WAI apprentice of the year 2018.

about us

Smith’s Heating Services Ltd is a family run, Gas Safe and Oftec registered business serving High Wycombe and surrounding areas.

We specialise in central heating systems and boiler installations, but also have wide knowledge and experience in most areas of plumbing. We are qualified and registered to work on Natural Gas, LPG and Oil. We are also qualified to install un-vented hot water systems and fully trained on UK Water regulations. We provide comprehensive advice, high-quality professional work and a personal service.

why choose us

Over 90% of our work comes from referrals! We don’t just want to fit a new boiler, we want to build a long-term relationship with customers and have many customers that have used us again when they have moved house.

get in touch

Got a question or need help? Don’t hesitate to contact us directly and we will be happy to assist you.


7 Derehams Lane
High Wycombe HP10 9RH



01494 328382

emergency plumbing

Imagine you come home one day to discover that a blocked pipe has flooded your home. You’re going to need professional help quickly!

8.00am – 6.00 pm Monday to Friday

If you have an emergency outside of these times please call, or email and we will do our best to assist.