Hot water from a combi boiler#
There are two actions to think about here.
Reduce the hot water supply temperature. Combi boilers have a dial on the front that controls the temperature at which hot water is supplied. You can set this to the lowest temperature that is comfortable at the taps. Building users tend to turn all dials they can reach to maximum, so if they can get to your boiler, you may want to think about how to prevent this.
Turn off hot-water preheat. On a combi-boiler, “hot water preheat” keeps a bit of water warm at all times in case you want to wash your hands. It makes the water in your tap run hot faster than it would without it, although if it’s a long way between the boiler and the tap you’ll never notice the difference.
Turn off the preheat on your Worcester combi boiler - the same website has instructions for many boilers
Button for turning off hot water preheat, Worcester Bosch
We have seen claims that in houses, hot water preheat typically accounts for 5-10% of the gas bill, but this will of course depend on the building and its occupants. In community buildings, keep in mind that the feature will supply faster hot water 24/7, but most community buildings don’t have anyone in overnight. If your building users really can’t tolerate the delay, on some boilers a more adventurous electrician can tie it to the heating time switch so that the water only preheats when people are in.
Insulate pipe runs. Community buildings typically have very long pipe runs from the boiler to the taps. If that means the water cools before it gets to the tap, you might be cranking up the supply temperature to compensate. It’s best to insulate the pipes you can. Slip-on DIY pipe insulation is cheap. Professional insulation installers have access to better materials and skills to insulate the difficult bits.
A new option we aren’t sure about
With wall-hung gas combi boilers, if you have hot water preheat off, you will get cold water at the tap until the boiler has kicked in well enough to supply hot water. There are a few suppliers offering a device you can use with a combi-boiler that will restrict the flow of water until the water is warm. This saves water, an important green action. In buildings with metered water, the general consensus is that the cost of the device plus its installation - a couple hundred pounds - will pay back. The suppliers also claim substantial gas savings and faster delivery of hot water to the taps, and there is one claim that it will pay back in houses with long pipe runs. If that is true, this would probably be a good action for many community buildings. It’s hard to know for sure. We don’t know of any community buildings that have one.