Unvented hot water heaters look very much like a traditional immersion heaters but with a very important difference.  Unlike immersion heaters unvented water heaters are pressurised and work on mains pressure cold water.  Because these water heaters are pressurised only qualified/certified tradesmen should install them or carry out any work on them.  This qualification/certification classes the tradesmen as a "Competent Person".


The reason for this is that there are a number of safety features on an unvented water heater designed to protect you, your family, your home or place of business.  Not all tradesmen carry this qualification/certification.  Like the Gas Safe register tradesmen who install, service or carry out work on unvented water heaters are periodically tested to renew their qualification/certification.  Just being Gas Safe Registered does not meet the required standard to work on unvented water heaters.  Tradesmen who hold this qualification/certification are also able to carry out work on any electrical installation associated with the unvented water heater.  Electricians should not carry out work on any part of the installation unless they hold the correct certification.


Unfortunately many electricians/plumbers and other tradesmen carry out work illegally on these heaters believing them to be simple immersion heaters.


At Dunnwell Plumbing & Heating we hold the required certification to install, service and carry out work on unvented water heaters.  Each plumber who is certified to carry out this type of work carries with them a photo ID card showing their registration number allowing them to carry out the work.


The installation and maintenance of this type of system falls within the scope of The Water Supply (Water Fittings) Regulations 1999 and Approved Document G3 of the Building Regulations.

What Can Happen


When an unvented water heaters safety features fail the effects can be devastating.


The picture on the left is of a detached house whose unvented water heater blew up taking with it most of the second floor of the house.  As you can see the force of the explosion blew open windows and took a large section of the exterior wall.  This sort of occurrence is very rare but shows what can happen if your water heater is not maintained by properly certified tradesmen.


If you have an unvented water heater that fails because it was not correctly installed or maintained then your buildings or contents insurance may not pay out.

How Much Does it Cost


The cost of a standard service is £100.  This includes checks and routine maintenance of the unvented cylinder and its safety features.  Additional labour is charged at our standard labour rate plus the cost of any replacement parts.

Building Regulations 2010 Approved Document G
This document gives details on sanitation, hot water safety and water efficiency and is correct to the date and version number listed on the document.
Building Regulations Approved Document G[...]
Adobe Acrobat document [1.8 MB]
The Water Supply (Water Fittings) Regulations 1999
The Water Fittings Regulations (or Byelaws in Scotland) are national requirements for the design, installation and maintenance of plumbing systems, water fittings and water-using appliances.
The Water Supply (Water Fittings) Regula[...]
Adobe Acrobat document [69.0 KB]

Do I Have An Unvented Water Heater?


Unvented water heaters can be heated by a number of methods including immersion heater elements so the best way to tell if you have an unvented water heater is to look at your user manual.


If you do not have a user manual you can take the details of your cylinder and look them up on the internet.  You can also look at how your water heater is supplied.  If your water comes from a cold water storage tank it is most likely an immersion heater.

What Work needs to be Carried Out?


Most manufacturers recommend that their water heaters are serviced on at least an annual basis.  This is primarily to ensure that the safety features fitted to protect you, your family, your home or business are in working order.

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Office Hours

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Wakefield Office

25 Bradford Road, East Ardsley

Wakefield, WF3 2HE

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