Vented or unvented water cylinder? Help please

[Goosegettingfat]

Combi boiler not appropriate. Large house (4 bathrooms, one of which will be an electric shower). Flow rate is 9L per minute. One shower downstairs is gravity fed (and is ok but not amazing). Others (upstairs) are electric at present but 2 won't be (house renovation in process!!) soon. So if we go for vented, we would need a pump I think (praying these aren't too noisy).... any opinions/ advice gratefully received!

how old is your house?

If you had to dig a trench between your inside stopcock and the pavement, what would be in the way?

An unvented hot water cylinder is a pressurised system which is fed directly from the cold mains water feed and therefore can deliver hot water at mains pressure, which is great for improving the performance of your shower and bath.

An unvented cylinder doesn’t require a cold water storage tank, which is ideal if you are pushed for space as well as offering more flexibility when siting the cylinder.

The water can either be heated directly via an immersion heater or indirectly via the central heating system, solar thermal technology or other renewal energy such as heat pumps and biomass.

A vented hot water cylinder needs an expansion tank and a pump. All pumps make a noise but, you can get a reduced noise pump.

A vented cylinder is much cheaper than an unvented cylinder.

Hope this helps.

If you can use an unvented, the performance will be best, but you will need much better flow. My questions are leading towards installing a new, larger water service pipe into the house. You will probably also need some larger pipes inside, depending what is already there.

You won't need to use electric showers, and you will find their performance woeful.

You need a flow rate of 20l per min for an unvented cylinder. If your incoming mains is the correct size and you still have poor flow rate an Accumulator would have to be installed to increase the flow rate to the unvented.
Accumulators look just like another cylinder and would sit beside the unvented.
Unvented is definitely the way to go and as Pigletjohn says don't bother with electric showers as you will be disappointed with the comparison.

Just make sure you get a G3 qualified engineer to install and ensure balanced cold feeds are installed to the bathrooms- otherwise every time some one turns on a tap somewhere in the house the person having a shower will loose pressure.

Also, before digging up your floor, check with your water company to see what the water pressure is in your area.
If you have low pressure, you would have to go with whatdoiknow's suggestion or get a vented cylinder.