Want to drain central heating.

The system has a small tap on the outside of our house - is it simply a 
case of opening this up and flushing it through?

Also - I want to add a product called Fernox to the new water in the 
system. How do I do this?

"Paul"  wrote in message 
news:hb-dndgXwPAwO1rfSa8jmA@karoo.co.uk...

> Want to drain central heating.
>
> The system has a small tap on the outside of our house - is it simply a 
> case of opening this up and flushing it through?


Yes (but see below). And before you start turn the electric to the central 
heating off as you do not want a pump to run with no water should the 
programmer call for heat .


>
> Also - I want to add a product called Fernox to the new water in the 
> system. How do I do this?


What sort of central heating systen do you have? Combi, fully pumped, 
gravity?
To drain fully pumped systems down you need to open the motorised valves to 
let the water out. With all systems you need to open the bleed valves on the 
rads to let air in and allow them to drain. Start upstairs and work down so 
that you get air sucked in and not the water from above pushed out.
If it is not a combi than there is often a bleed valve next to and just 
above the hot water tank.This will also need opening.

To add Fernox then pour it into the header tank for vented systems before 
you refill with water and on a combi system put the fermox into an empty 
radiator.

If you have a mains pressure unvented system than you should not be touching 
it at all.

Have a look at

http://www.diyfaq.org.uk/plumbing/plumbingpage1.html

HTH

Adam