Water supply to direct un-vented hot water cylinder.

I want to install a direct un-vented hot water cylinder in a flat. The install instructions call for 22mm diameter water supply line, the main riser supply to the building is 22m and then reduces to 15mm before the stop valve. Do i need to isolate the main riser into the building in order to replace the 15mm stop valve with 22mm or can I step up the pipe diameter back to 22m after the 15mm stop valve without affecting the performance of the cylinder.

If the unvented cylinder is over 15 litres you must have an Unvented Hot Water certificate to do this work.

Owain

I rather like the idea of an unvented certificate. Is that really it's name?

I'd have thought that this was a little academic, unless the person is incredibly stupid and sets thermostats to try to make the tank into a steam engine. also does not say how far this 15mm runs for and what the cylinder is supposed to be feeding either.

Yes I've not come across unvented certificates, only the people issuing things tend to vent a lot...:-)

Brian

It was called G3 Unvented Hot Water but it's now been overtaken by changes in Building Regs and the certificate now covers all hot water systems.

England/Wales covers Approved Document G3, Part L1 and Part P of the Building Regulations, while the one for Scotland references Part J of the Building Standards

Also, if not a member of a Competent Persons scheme, notification to Building Control is required.

Owain

Do you actually need a sustificate to work on such a system, or just to sign it off for BC?

AIUI both, a sustificate to comply with Water Regulations, and to sign it off for BC (or membership of a scheme to self-certify it to BC)

Owain

Yes, it comes in a sealed container.

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Do you need one to do such work in your own property? ie not for reward.

Again AIUI, yes.

Owain

So not like gas then? Which just requires a "competent person" unless working for reward.