Unvented water heater Vented or ‘Open Outlet’ water heaters are popular choices for localised water heating, often used where there is no central boiler or that boiler is a long way away. The advantage of a ‘Vented’ heater over an unvented heater, is that there is no need for expansion vessels or lengths of pipework which can accommodate the expansion of the water as it is heated – so its installation is simpler, especially where space is at a premium.

However, there are 4 important things you need to know about this type of water heater:

  1.  Get the right taps!

Particular care must be taken when choosing the taps to be used with the units, because they need special ‘vented’ taps. The only situation where this is not the case is where they are situated over a sink and the unit dispenses the water through a spout rather than a tap.

If you fit a vented heater to normal, unvented taps – your water tank will almost certainly burst – a dangerous and costly experience.

  1. Don’t worry about the tap dripping!

As the water is being heated, it expands, and it is designed to vent through the tap – this means that the hot tap will sometime drip a little. THIS IS PERFECTLY NORMAL. If the heater is in a location where many different people will use it (such as a village hall) we would recommend putting up a sign telling people not to turn the tap off as tightly as they can: we often get customers needing to buy new taps as they have been broken by users desperately trying stop the tap dripping.

  1. Only one sink per heater!

You need one heater per sink (or to be more precise, one heater per vented tap) for this system to work properly. Trying to add more taps will result in very strange things happening (like the second tap working when you turn the first tap on!).

  1. The plumbing is not like an unvented heater.

This fact is often a useful way to verify whether you have an existing unvented heater. From the diagram below, you can see how these units are plumbed in. The striking difference is that although the unit will have 2 pipe connections, it is not as simple as one being connected to the cold inlet and the other connected to the hot tap: as you can see from the diagram, they both connect to the connections on the vented hot tap.

Vented electric water heaters are also called ‘Point of use’, ‘Displacement’, Non-pressure’ or ‘open outlet’ heaters.

How do vented water heaters work

If you have any doubts about whether you are buying the right heater, or whether you have the right taps for it, please call our experts on 01934 253600.