Adding inhibitor to combi system

[Timothy Smith]

Hi there

Sorry if this has been answered before but I did have a look and couldnt find it.

I drained our combi system three or four months back and when I refilled it I forgot to add inhibitor.

Now Ive remembered Im trying to figure out where to add it. The only possibles are the filling valve or a radiator bleed valve as far as I can see.

Can anyone tell me the correct method ?

Thanks

Tim

[Lobster]

There's not really a right or wrong method; just add it whereever's most convenient and causes least hassle. For me, it's a towel rail with a bleed valve pointing upwards, so if I just remove that I can simply stand a funnel in there I can pour in however much inhibitor. An ordinary horizontal bleed valve is do-able but you'll need to attach a length of hose to your funnel. (you need to remove the whole valve fitting from the rad, not just the tiny needle-bit)

You'll need to drain off an equivalent volume of liquid elsewhere of course.

Or remove an upstairs radiator and pour inhibitor into the exposed pipe stem?

You can also get highly concentrated inhibitor pre-packed in a syringe, which can make life easier.

David

[chris French]

In message , Timothy Smith writes

Any that works?

You can get Fernox inhibitor in a big syringe type affair that attaches to the top tappings on the radiator.

I put it normally via one of the upstairs radiators. We used to have a ladder type radiator in the bathroom, this was easiest. Drain down the system a little, remove one of the plugs from the top tappings, stick in a funnel pour in inhibitor. Replace plug, top up system and repressurise.

When we didn't have a ladder radiator I had a a bit of flexible plastic pipe - in this case 15mm Hep2O pipe - but hose pipe or whatever is around, a compression - to - threaded fitting on the end. Screwed this into the top tapping on the radiator and put the funnel in that.

[Timothy Smith]

Thanks Chris

[Christian McArdle]

It depends if you don't mind doing a bit of plumbing.

You're supposed to use a messy injector syringe which sprays the inhibitor all over the room.

Personally, I prefer to add an additive injection point. This consists of a 'T' fitting near the top of the system (you can have it lower, but need to be able to drain below the point). The 'T' has a short length of pipe upwards, a reliable isolation valve and then a funnel. I used a tank connector and a small (i.e. 10cm diameter) tupperware box for this.

To insert chemicals, you drain well below the point, open the valve and pour in whatever chemicals are required. When finished, close the valve and refill with water.

This technique allows you to use cheaper chemicals without spilling a thing.

Christian.

[Matt]

Or if you have a towel rail then close all the other radiator valves except the towel rail, part drain the system (if you drain to a bucket you can see how much has come out) take off the bleed valve/blanking plug, pour in the inhibitor, tighten everything up, refill and rebleed, check the pressure again and adjust as necessary. Start to finish it could take less than an hour. Of course without a towel rail you are knackered.

[Christian McArdle]

Technically you can use this technique with any radiator, although it helps if the bleed valve unit hasn't been painted to the radiator.

Christian.

[john]

I think that new instalations should have two features: 1. A proper outside drain point with a valve in the house. 2. A means of dosing the system.

3 - possibly a place to attract sludge and allow it to be removed - a bit like the traps on compressed air systems. Ideally transparent so that you can see the colour of the circulating gunge.

John