Despite using fernox cleaner a year or so back - left running for a week in the system IIRC, I recently had to clear a blockage of powdery magnetite from a central heating 15mm plastic radiator feed.
Does anyone have good experience of FerroQuest by Sentinel (or any other similar product) which is likely to dissolve and remove this sort of residue? The blockage removed was more like finely ground coal than a powdery sludge usually flushed through rads!
8 rads have been removed and been thoroughly blasted through or replaced, 6 have not been disturbed.
This would suggest that either you have a problem with introduction of air, or that the system was somewhat clogged before and material moved around.
I think that you may have described your problem. Chemical cleaners can only do so much in terms of loosening or removing crud.
If you just cleaned half the system mechanically, then it's quite likely that there is a fair amount of material left and some moved around.
Some while ago I wrote up some notes on what I did to do a thorough system clean.
In short it involved:
- Taking off radiators one at a time and flushing them outside. (Care because the sludge stains)
- Using the header tank or filling loop, flush at each radiator valve while radiator is removed.
- Refit and refill using a system cleaner. Run hot as appropriate.
- Thoroughly flush again and refill adding inhibitor.
This avoids crud being circulated around the system. It has to leave by the shortest exit. Obviously it works better on a sealed system because you can flush with mains pressure.
Do you know whether these cleaners can actually redissolve this granular type material? The only drain on my system (concrete ground floors) is on a radiator return pipe. So I am reliant on the debris "floating" out of the system.
I am pretty sure that the effect is minimal when there are large amounts of material. At best, I suspect that it might dislodge some, and that this is what is happening - i.e. travelling from A to B.
Then the problem is that it can tend to collect and block.
I've only ever used this stuff after a mechanical clean to do a final cleanup.
Oh I see. You mean that the pipes come out of the floor?
In that case, I think that I would try to come up with a way to force water through and out at each radiator valve.
If you have an open vent system, this is going to be tricky because you can't get a lot of pressure.
A couple of ideas spring to mind (assuming you don't want to convert to a sealed system):
- Rent a pressure flushing machine.
- Temporarily (note temporarily) fit valves to the feed pipe and vent pipe in the loft. Fit a valve to hook up a hose at a convenient point on the system (don't use the drain outlet because it will tend to leak). Disconnect downstairs radiators one at a time and flush out at each radiator valve. Obviously great care is needed to avoid staining furnishings and floors.
Once you've done this and got a clean system, make sure that there is no sucking down the vent pipe. THen use flushing agent for a while, drain, flush with plain water and refill with inhibitor added.
You probably could continue a little at a time, but it will remain a perennial PITA.
This is where the plumbing layout, and pump position are such that there is a significant pressure differential between the vent and the feed pipes. If it is in one direction, there can be pump over - water trickles from vent into tank. In the other, air is sucked down the vent. Either one causes repeated oxygenation of the water, although suckdown tends to also produce a build up of air in radiators.
It is caused if there is a pressure differential between the two places where vent and feed pipes connect to the system and is quite likely to happen if they are on opposite sides of the pump. However, as little as a 30cm length of pipe between the two can cause problems.
Generally the best way is to make sure that they connect to points no more than 15cm apart or to an air separator like a Myson Aerjec.
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