My pressurised central heating system - maintenance/cleaning

[AngusE]

Bear with me here - my basic knowledge comes from reading online, not experience. I live in a 2 bed apartment with main bathroom and ensuite. Property has a pressurised CH system driven by a Potterton PowerMax HE boiler (a large free-standing combi boiler with the "benefits" of a built in 115L hot water tank) which is the same age as the property (10 years). I have owned the property for 2 years.

Symptoms:

1. Humidity has caused corrosion to both bathroom radiators - worse in the ensuite which has no window.
2. I removed the ensuite radiator to replace it but noticed that the water released has black sediment (I'd describe it as sediment rather than sludge). Also, the water remains light brown even when the sediment settles (evidence of some rust in system).
3. The pressure indicator on the boiler shows a SLOW drop in pressure - I need to top the system up every couple of weeks.

The challenges:

My primary objective was to replace the 2 bathroom radiators and then refill the system and add fresh inhibitor (I do not know if the inhibitor has ever been replaced - I doubt it - but it is certainly being diluted by the pressure top-ups).

However, I now see that I also need to clean out any existing "gunk" and then refill the system. A power flush seems to be an expensive proposition (also because they apparently use a lot of water and my supply is metered).

So then I thought maybe I could introduce a cleaner (e.g Sentinel X400) - run that in the system for a while and then drain it all off, refill and introduce a leak sealer like Fernox F4) to seek out any small gaps causing the pressure drop, then drain again and refill, adding a suitable inhibitor. And I would also like to add a magnetic filter (e.gAdey Magnaclean) to prevent/delay future problems

HOWEVER, I cannot see an obvious way to drain down the system. My apartment is on one level with concrete floors so everything is on a single level. There is no drain-down valve on any radiator. If I drain each radiator at the TRV/Lockshield water will only train as low as the valves and just sit in all other pipework (which is plastic behind the walls by the way).

It is effectively impossible to access the pipework below the boiler - there is no exposed pipework because the boiler is on a plinth (about 8" high) supported by very think (2") pieces of wood. Not a very helpful installation!

So, no obvious way to drain down and no exposed length of pipework on the CH return outside the boiler cabinet to install a magnetic cleaner. A challenging installation but it's important I find some cost effective solutions before there is further degradation in the radiator system and/or the boiler.

SUGGESTIONS???

 

[ShaunCorbs]

Your best bet as it sounds like you will need to change Pipework and add a few drain offs

 

[jtsplumbing]

Have yo had a look outside to see if any drain points poking out of wall ? if not replace ground floor lock shield valves with ones that have a drain off valve incorporated, once you have some drain points Add Fernox F5 Heavy duty cleaner , run system for a week, drain whole o system (When Hot) if you have the time & someone to help remove radiators , take out side turn up side down and flush through with a hose pipe, refit refill system and flush with clean water to clear pipe work, refill system and add Fernox F1inhibitor, Its that I prefer Fernox product's to sentinel , always seems to do the job better & quicker, Whatever method you use it will involve using a lot of water there is no way to cleanse a system without using a lot of water, drop in pressure may be due to a drip on a radiator valve or something in boiler when was boiler last serviced ?