Unvented, do I need new hot/cold water piping?

[andy.budgell]

Hi All,


I currently have a vented hot water system.
I'm getting quotes for unvented, mains pressure.

What modifications in terms of hot/cold water pipework changes within the house will be needed so that the shower will not be affected when someone else flushes the toilet, washes their hands in the cloakroom toilet? At the moment, I have a surrey flange for hot and separate cold feed from tank for power shower. But I know the power shower has to go, and obviously all tanks will also go.

The current cylinder is in the airing cupboard. The new cylinder will be in the garage. I'll be getting a normal mixer shower in the bathroom.

This advice would be most useful when I have the plumbers around giving me quotes! I am aware of a balancing valve, but still unsure how effective it is? Any anecdotes anyone?
Cheers
Andy

 

[gas4you]

You will need 22mm cold mains to the unvented cylinder, at least 3 bar incoming pressure and hopefully around 20 litres/min flow. What size is your cold mains to your internal stopcock? Needs to be 25mm.

The hot from the current surrey flange will just be connected into the new hot outlet on the cylinder. The seperate cold feed from your loft storage tank will need to be teed in after the pressure reducung valve that will come with the new cylinder.

 

[andy.budgell]

Cheers gas4you.

I know for sure that the incoming mains is an old imperial size around 20mm as I had to move up the stop cock for another project. Its not 25mm thats for sure. Will this be a problem?

As for the power shower, I was told I couldnt have this with a mains pressure hot water system?

I've also been advised that I need 22mm Cold to the bathroom, its currently 15mm?

 

[gas4you]

No you can't have a power shower with mains unvented. Is your 20mm cold mains lead or iron? If so probably only the equivalent to 15mm. Unless you have got excellent pressure you may have problems and not get the full potential benefits from the un-vented cylinder

 

[andy.budgell]

The cold water inlet is black plastic. Blinking tough plastic I seem to remember. I think it may have had a metal inner too.

Oh dear, sounds like there could a few issues then. Waterboard to run a 25mm from main pipe?

Does that mean I'll have the pressure but not the flow rate?