help for novice to drain down and refill system

29 Sep 2011
Reaction score
United Kingdom
Hi. I have had loads of noise when my hot water turns on for months now. Like a gushing, trickling kettling noise. A mate who is good with all things like this suggested we drain down the system as it would probably be full of sludge. So did this yesterday and :eek: . Water was jet black. The house is 12 years old and it has never had any sludge remover or inhibitor fitted.
With this in mind I want to drain it down again, add the cleaner, leave a few weeks, drain and add an inhibitor. Just wanted to check if I'm doing things here in the right order. I believe it is an open vented system, conventional boiler (ideal classic).

1. Isolate tank in loft
2. Attach hose to downstairs rad and crack this open
3. Open bleed valves on upstairs rads and then the same downstairs
4. When drained close all bleed valves
5. Open valve in loft to fill header tank and leave to fill
6. Open bleed valves downstairs first one at a time so they fill and then the same upstairs.

This is the order we did things yesterday but since then i am thinking of the following. The diverter valve has a position for "flushing only" (didnt touch this yesterday) Should I move the lever to this position before draining and will this drain water from the coil in the hot water tank in the airing cupboard? If so do I open the bleed valve feeding into this tank (as in the photo below)
Also when the system fills when do I bleed air from the pump and this bleed valve in the cupboard?
Also I have seen that the boiler should be off. I take it this means not firing and so knock the electricity off yes? Also just read in the FAQ section theat the pump should be set to manual. The pump is a Grundfos Selectric and has no manual controls.
Any tips for a novice would be great?

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