adding cleaner/inhibitor to a standard central heating system

[quartzz]

Hi, possibly newb question I guess. Basically just want to add some cleaner to the heating pipework system, leave it for 24/48 hours to circulate, then flush (I think this is the right term) and refill with including inhibitor?

House system is 4 radiators + 1 towel rail heater (can pour liquid into the top of it). warmflow oil powered combi boiler if that is relevent

The theory/plan is (if anyone could tell me why this won't work)

1 - Drain 1.5L of water from entire system by releasing one of the valves at the "bottom" of the heating system (probably living room) then of course re seal valve
2 - open towel rail heater ("top" of the system) and pour in something like 1L of sentinel x300 or x400 cleaner (other brands are probably available)
3 - seal system back up, and run the whole house for 24/48 hours or so (might involve a gentle bash with a rubber mallet on each rad?)
4 - after 24/48 hours (turn everything off) open up the seal in (1), and drain the entire system out - any old gunk/sludge/particles would hopefully come out through the valve?
5 - reseal valve in (1) (so now have empty pipework), open up the towel heater valve again, and refill jug by jug with tap water
6 - when the pipework is full again (or 1L less than full), pour in some sentinel inhibitor

(4) would include measuring out how much old water came out, so I know how much is needed to re fill it

 

[CountryFan]

I take you know that the system needs a clean?

 

[quartzz]

well - no. I moved into the property Oct 2024, I have no idea what state the water inside the pipework is like and no idea what condition the radiators are in (although they all seem to be heating up with no apparent cold spots [he says, current situation]). "prevention better than cure" type approach? Would the above procedure work - or is there more to it and extra complications? (Yes I know.....there can always be complications)

 

[CountryFan]

If you’re going to drain the system after cleaning, you need to drain all ground floor radiators. I know you’ve said prevention is better than cure, but what if there’s already inhibitor in the system, it would then seem a pointless exercise. You could have the water quality tested for inhibitor if there’s no labels or benchmark filled in to ascertain this.

 

[quartzz]

I suppose there's a few questions. I have (in my mind) divided the operation into two steps - firstly adding the cleaner, by draining about 1.5L of water from a single low point in the pipework (living room), then secondly (after a few days), draining and re filling with inhibitor.

Presumably I would need to do the second complete draining operation to get gunk and particles out of the pipework

I've mastered bleeding (one) of the radiators (the kitchen one), would bleeding this single rad remove air from the entire pipework system? Or do each of the 4 rads need separate bleeding

When I moved in here the kitchen rad wasn't heating up, I thought it might need bleeding, so did the square valve tweak, and just water came out. I found the actual cause was a stuck thermostatic pin valve (I moved in 3 weeks after previous occupiers moved out, so might have just seized). Would removing 50ml of water from one of the rads, mean the entire house pipework system is now missing 50ml water?

Is there any way to find out the current "gunk situation" and "inhibitor content"? Would I need to do that rad by rad?