Don't waste your money on a course. I learned all I needed from library books; there are plenty in Croydon libraries - I used to borrow them. The £300 you save will then go towards the cost of the rads and any other bits you need.
You can also get plenty of
free advice from this forum, so here goes.
Assuming you intend doing this when the weather is warmer, you can start by getting two cans of Sentinel X400 cleaner, adding the contents to your system and leaving it there until you start the work. This will loosen all the sludge in the system and make it easier to flush through.
If you have a conventional boiler,with a small tank in the loft, you do it this way:
1. Tie up the ball valve
2. Bail out the water until it is just above the pipe exit at the bottom
Carefully remove all the sludge etc in the tank, making sure none goes down the pipe at the bottom of the tank
3. Add the X400 to the tank
4. Untie ball valve and let the tank fill
5. Retie ball valve
The next bit requires two people - on in the loft
6. Locate a drain point (usually on a ground floor radiator valve) and
drain off some water until the level in the tank falls to just above the lower outlet (that's why you need someone in the loft
)
7. Untie ball valve.
If you have a combi or system boiler it is probably best to use the X400 Concentrate or Rapid-Dose and put it in via the filling loop or a radiator bleed valve. Instructions are on the cannister.
As for the actual job of changing rads, do you intend to change just the rad or do you want to replace the rad and the valves either side? The procedure is different. Also do you intend installing new TRVs?
Tell us what you intend doing.
Also tell us more about your existing system - boiler make and model would do for a start.
What sort of boiler are you thinking of installing - conventional, combi or system?
Lastly, £8000 sound a bit steep. Was it from British Gas or another large conglomerate? If so, get quotes from smaller independent installers.
