Adding Corrosion Inhibitor with old(ish) radiators

[Bowness72]

Hi,

I need to add corrosion inhibitor to my central heating system (Worcester Bosch Combi). I have read several threads online about doing this via the radiator bleed nipple but am not sure this will be easy with my system. The radiators are probably about 20 years old and don't have the bleed valve on the end, they just have the small pin at the back facing the wall. I can imagine that it might be difficult to add corrosion inhibitor through this ?
I'm no plumber but have done some basic plumbing before so my intention is to drain down the system, fill up again, and drain down again to help flush out the system, including adding flushing agent if necessary.

As I understand it, my options for adding the inhibitor are....
1. Filling loop
2. Bleed nipple

Or would it be possible to inject through the drain valve instead of the bleed valve ?

Thanks

 

[Burnerman]

Just check out Fernox F1 Express......this is effectively a pressurised container of inhibitor with a variety of connectors to the filling loop or radiator valves.
I'd depressurise the system, leave one bleed nipple open, inject the inhibitor through the filling loop, close valves and then repressurise.
John
(Worcester oil Heatslave)

 

[Bowness72]

Thanks for that Burnerman but I'm not sure how to make the connection at my filling loop as it doesn't have the usual filling loop, it has the internal filling link and key, which is why I was looking for a different way to do it.

 

[Burnerman]

Alas I was afraid you'd say that!
The inhibitor kit will inject through a bleed valve, if you have one that's easier to access anywhere?
You could theoretically add via a drain down point but of course there's a chance the chemical would just rush back out again as you were fumbling with the square headed insert - not to mention the aggro if the washer was nacked anyway!
Maybe there's another way of introducing the chemical into this boiler, but I wouldn't know.
Anyway before you rush in, is any water that comes out of the bleed valves black? There may be little point introducing inhibitor into a dirty system.
John

 

[Bowness72]

Thanks for your input Burnerman... Yes, there is black water in the pipes. Unfortunately I found this out last week when I was renovating my bathroom and stupidly put a drill bit through the floor and pipe.
My plan is/was to drain and refill a couple of times and then add inhibitor. Are you saying this might be a pointless exercise ?

 

[Burnerman]

When I had this issue with my 1960 house, I actually took the rads off and connected them to a hose pipe in the garden ......I'm afraid draining and refilling won't release much of the crap that's lurking.
A power flush is another way of cleaning out, of course and there are many posts covering this.
John

 

[Bowness72]

Thanks Burnerman. Back to the drawing board for me then. I had considered doing the hosepipe cleaning method.

 

[Burnerman]

Only my opinion of course - as a householder rather than a heating engineer!
John

 

[JohnD]

you can add Sentinel X400 and circulate it for a few weeks. It will loosen the old sludge so you get more out in the drain and flush.

Adding a system filter will help trap whatever remains and is circulating in the water.

 

[Elkato531]

If you're draining down and can fit a system filter, this can be used for addition of inhibitor. If not adding a filter why not just cut in a T at a convenient point which can be used to add chemicals and then capped.