6 THINGS TO CONSIDER BEFORE BUYING A COMBI BOILER

​Are you considering getting rid of your old hot water cylinder and converting your heating system to a combination boiler?

This is a common choice for many households and has a number of advantages. ​

1. It frees up more space by removing the hot water cylinder and leaving just the boiler on the wall. This means you could have more space in your kitchen. Or you could have storage capacity in your old airing cupboard.
2. It’s more efficient than heating a large tank of hot water. With a combi boiler, you only heat the water you use, so less wasted energy.
3. Increased water pressure. Instead of the hot water being fed from a tank in the loft, it comes directly from the main water supply, meaning an increased flow rate through the taps and a more powerful shower when compared to a gravity system.

For small to medium sized houses, combi boilers can be an ideal choice. But they don’t suit every household.

There are a number of factors to consider when looking at installing a combi boiler. From the location of the boiler to whether it’s right for your household.
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These factors impact the viability of the job, cost of installation and the likely location of the boiler.

1. Gas pipe size

Because a gas boiler has to burn more gas to heat your hot water quickly, it is likely that your existing gas pipe will be too small. To deliver the right volume of gas at the correct pressure, the pipe has to be sized correctly. This means that a new larger bore gas pipe will need to be installed between your gas meter and the position of the new boiler.

This often means running a copper pipe externally round your house, or lifting carpets and  floorboards to install the gas pipe inside.

This is often a factor in determining the best location for your new combi boiler.

2. Number of bathrooms

If you live in larger house or have more than one bathroom, a combi boiler might not be the right option for you.

Most combis are designed to run one hot tap or shower at a time. If you have two showers in the house, using them both at the same time will cause very poor water flow through one or both showers.

3. Your current shower

If you have an electric power shower, this will not work with a combi boiler. These showers have a pump built into the unit in your bathroom and are designed to be fed at low pressure from the tanks in your loft. Putting a combi boiler on these units will quickly cause a leak.

So if you have one of these showers, this will need to be replaced with a standard thermostatic mixer unit. This is likely to mean re-tiling at least a section of your bathroom wall.

If you have a shower pump in your airing cupboard or an electric shower that runs directly off the mains water supply, the change to a combi boiler is much simpler. The electric shower can stay. The remote shower pump simply gets removed and bypassed.

4. Hot and cold water connections

Your old boiler has two water connections – the flow and return pipes for your heating. Your new combi boiler will also have a cold water inlet and hot water outlet.

If you’re fitting the boiler in your kitchen or utility, it is common to run the hot and cold pipes from under or near the sink. For ease of connection, a heating adviser might suggest locating the new boiler in your airing cupboard, where there are already heating, cold water and hot water pipes.

5. Your existing hot water system

We have occasionally been asked about removing an unvented hot water cylinder and replacing it with a combi boiler. Our strong advise here is, don’t do it!

An unvented or pressurised hot water cylinder delivers high pressure water at a good flow rate to multiple outlets.

Removing this cylinder and replacing it with a combi would reduce your hot water capacity significantly.

6. Condensate

Modern boilers produce condensation which runs out of the bottom of the boiler and into a drain. If your existing boiler doesn’t have a condensation outlet then provision needs to be made for the safe disposal of this water.

If you’re moving your boiler to an airing cupboard you can sometimes run the condensation pipe into the bathroom. If this isn’t possible, the water can run into a condensate pump, which sends the waste water into a remote outlet, such as your soil pipe. This would add to the overall cost of the installation.
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Combination boilers are available for use with natural gas, LPG or oil.  Should you be considering changing your system to a combi boiler, it is always best to consult a heating expert before making a decision.

If you live near Peterborough or Stamford, we’d be happy to give you any advice you need.