Inhibitor Top Up After Changing Rads.

[sddsddean]

We've got a 4 bed house with 6 rads downstairs and 6 upstairs. I'm going to change 3 of the upstairs rads. Last time inhibitor was topped up was about 10 years ago. Is it worth topping up the system with 1 litre of inhibitor? I don't really want to drain the system down and can just pour the inhibitor into the header tank (not a combi system). Thanks for any advice.

[Hymie]

If you are going to replace three radiators, even if you can achieve this without draining the system, the new radiators will need filling which will be via the header tank. So once you have replaced the radiators (and before re-filling) you could add the inhibitor to the header tank. The volume of the header tank is unlikely to fill three radiators.

If you want to ensure the complete 1 litre of inhibitor is added to the radiator system (with none remaining in the header tank) after adding the inhibitor, re-fill the system with the tank ball-cock held in the up position until the tank is almost drained.

I would certainly add the recommend amount of inhibitor – but I know of others who don’t believe in the stuff.

[youngmafbog]

Just do what Hymie suggests in para 1

Add the inhibitor to the tank before refilling then just refill.

Personally after 10 years I'd drain and refill the whole system.

[bhg481]

I agree with Hymie. I use Fernox in our system which recommends checking after about 7 years but I just add a 5-litre bottle to the system (after removing a bit from the header tank, if necessary). We've lived in the house for about 40 years now, including adding a couple of radiators when we extended, and never have to bleed the system. Only repairs have been one replacement pump, so we must be doing something right.

[sddsddean]

Thanks for all the info…very helpful. One other question…is there a rule of thumb on how much inhibitor to add? I was just going to put 1 litre in, but see big says he puts in 5 litres. Can you put too much in?
Thanks.

[sddsddean]

Sorry bhg…autocorrect!!

[bhg481]

I use Fernox MB-1 which comes in 4 litre bottles (not 5 litre as I said earlier), which Fernox say is sufficient for a 3 or 4 bedroom house. They suggest you test it annually with one of their test kits; years ago they used to tell you to draw a bit off and see if a nail goes rusty in it after 7 years. For simplicity I just add 4 litres every 7 years or so; works for me.

[sddsddean]

Thanks bhg