Vented vs unvented cylinder

2 Jan 2012
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United Kingdom
I'm looking at cylinders for a renovation and the heating engineer has suggested an unvented cylinder. I have a few q's I could do with some help on never having had an unvented:

I have 15mm mains and I know that with the correct pressure and flow that could be okay subject to the HE confirming. Does this mean I have 15mm running everywhere for hot and cold?

If I want to change plumbing later when I have the kitchen changed, does that require a HE to do the work? Or is there a way to turn off the connection from the cylinder to the taps without a HE?

Can I really justify this over a vented system with a pump for shower pressure? The house has just one bathroom.

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Unless its a one bed flat with a single shower/bath, 15mm is not adequate.

Look at the box below for a few of the thousand identical threads already posted on the subject.
With U/V hot water you really need 22mm Cold main to ensure sufficient flow rates as long as you meet the necessary pressure and flow rate
unvented is the "modern" way to go! however any doubt about the flow & pressure then I would go with roof tanks and a vented cylinder
a site visit would be necessary to confirm ;)

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