"Peter Cherry" wrote in message
m...

Hi, I have another query with regard to my own plumbing this time that
I would like some advice on please. We are building an extension at
the moment and need to run water from the current house into the
extension. Without going into all the reasons why, I am considering
upgrading the gravity fed hot water cylinder to a pressurised one.

The cost of these cylinders in the UK seems over the top, but a friend
recently told me they were much cheaper in France & he had a recent
Brico Depot catalogue to hand. A 150 ltr cylinder costs 99 Euros
fitted with a 1800w immersion heater, a 200 ltr is even cheaper at 90
Euros! I understand that these do not have a coil inside them so I
could not hook it up to my existing C/H system. This does not bother
me, it does not seem to cost much more whether I heat off gas or
electric from past experience.

What! Gas is 3 to 4 times cheaper than electricity per kW. You haven't
looked at your bills closely enough.

According to him, you just plumb them
in, connect the water pipes up and away you go.

Has anyone any experience of fitting these things & can offer any
advice?

My questions a

Will these tanks fit up to my existing 22mm plumbing connections OK ?

If not adaptors are available from continental sizes to ours. The French
use BSP sizes for threads

Can anyone forsee any problems modifying my C/H system as the pipes
won't go through the HW cylinder any longer ?

Would I be breaking any regulations and/or should the building
inspector be involved ?

A BBA approved installer has to fit an unvented cylidner. You can't do it
yourself.

Do I have to fit a vent pipe (think I do)?

No. a 1" over flow pipe with tundish on it.

Can anyone forsee any other problems ?

Britiush unvented cylidner have more safety protectiopn on them than
continental versions.

An unvented system consists of:

- Expansion vessel. An external pressure vessel or internal pressure air
pocket.
- A high-pressure relief valve. If pressure exceeds the set limit the valve
opens releasing pressure to a safe level.
- A high-temperature relief valve. If high temperatures occur, typically
90-95C, the valve opens to amtosphere..
- Non-return valve. To prevent cylinder implosions and back-pressure into
the cold mains supply pipe.
- Pressure reducing valve. To reduce the inlet pressure to a working
pressure of typically 2 bar for copper and 3.5 bar for steel cylinders.

If it doesn't have the above it will not conform to UK specs and be illegal.

Have you tried looking at a thermal store, as you can DIY these. There are
some cheapish ones about.