Unvented hot water cylinder

[audi321]

Hi all, I've bought an unvented HW tank and it (quite rightly) specifies that an expansion vessel must be fitted.

However in the manual, it says that it should be fitted to the cold water inlet side rather than the hot outlet.

To me that sounds wrong? Anyone any experience with these?

[Black_S3]

You should have a combi valve that comes with it theres a connection on there for the expansion vessel. It does need someone with their unvented/G3 ticket to fit it though and ideally someone who can certify it/register it with building control - ideally if it's heated via a gas boiler and the installer has the tickets they can certify it via gas safe who also do the building control bit for less than £5 - If its a direct cylinder someone with NICEIC certification and G3 is better. Getting them certified yourself directly by building control can be expensive at possibly £500.

They can be pretty dangerous if not fitted correctly with all the saftey devices working so definitly not a DIY job.

[audi321]

Cheers. It s a direct one so no gas involved

[Black_S3]

Def worth making sure whoevers fitting it gets the D1 and D2 pipes correct as thats largely what building control focus on.

[IJWS15]

Fitting these isn’t really a DIY job and they should have an annual service.

When you come to sell the house you will be asked for paperwork which you don’t get by DIYingit.

[Black_S3]

IJWS15 said:

Fitting these isn t really a DIY job and they should have an annual service.

When you come to sell the house you will be asked for paperwork which you don t get by DIYingit.

Yup and that paperwork later on costs nearly the same as the cost of an installer who can certify.

[Brinyan]

To the original question, the expansion vessel is connected to the cold feed, not the hot outlet pipe. Some of the combination valves have a connection for the vessel to connect to, but mostly it’s connected via a pipe taken from the cold feed, after the combination valve.
Get a registered installer to carry out the installation & notify Building Control, who will issue a certificate to say it’s been installed by a competent person.