Testing Inhibitor in heating system

[mangroa]

Hi,
I was wondering how to test if my heating system has enough inhibitor in it. I though that I'd take a sample of the water from the header tank and drop some iron nails into it to see if they rusted.
I did the same with tap water for a control sample.

The tap water nails rusted over night. The nails in the heating water took a few days, but they did develop rust on them. Much less than the tap water.

Is this a good test? Do I need to do anything to protect my system?

I had a boiler fitted about 3 years ago, the system hasnt been drained since.

Thanks
Alan

 

[ChrisR]

A sample from a drain cock would have been more representative of what's in the radiators because the header is more aerated.
The nails shouldn't rust at all though, so I'd just tip some more in. It'll work its way in as the water level goes up and down on heating/cooling, though you can drain water to get it straight in. Use Sentinel or Fernox inhibitor.

 

[mangroa]

Thanks for the fast reply.
Ok, I'll get a sample from draincock and do the test again.

 

[ChrisR]

Cheapskate

 

[mangroa]

Yep, I am

Is it possible to have too much fernox in there?
Its just an average 3 bed semi with 9 rads.

 

[ChrisR]

No. I know a guy who puts another litre in every year. Pristine system!

 

[mangroa]

sweet, I'll get some at the weekend.
Thanks for your help!