How much inhibitor for only three rads?

[Lucky Luke]

Hello — I'm mithering you experts again, only just after having one C.H.problem solved on this forum. Our boiler-fed heating system has only three radiators (yes, three), and we have our own good reasons for this. However, I intend to have the boiler replaced, and want to start off on the right foot. Would five litres of inhibitor be too much? I once asked a Vaillant engineer, servicing our boiler, whether a system can be given too much inhibitor, and he said Yes, it can. Others (on this forum) seem not to care how much goes in, so I don't know what to think. I would be glad to have another answer to my question though. I don't mind paying for more than is needed (Vaillant have a standard dose of 5 litres, I think), as long as it does no harm to the boiler. It's better to be safe than sorry.

With thanks for any informed replies,
L.L.

 

[Mottie]

Would five litres of inhibitor be too much?

It'd certainly be a waste of money. I have 10 rads and one litre is enough. I think most people with roughly the same rads would have one litre too. For your setup, half a litre would be enough.

 

[Madrab]

Vaillant wouldn't have a standard dose, they have no idea the size of system their boiler's being fitted to, as such it's all down to the volume of the system/number of rads. A 1tr or 500ml bottle (brand dependent) is usually enough for up to 10 'standard' sized rads,, so one would be more than enough.

 

[terryplumb]

5 litres ,I don't think so !!
Half a litre would be plenty for your needs

 

[Lucky Luke]

It'd certainly be a waste of money. I have 10 rads and one litre is enough. I think most people with roughly the same rads would have one litre too. For your setup, half a litre would be enough.

Thanks, Mottie (and you others that have replied, saying much the same as Mottie). However, with one part of my query, I suppose I shall have to draw my own conclusions, which is that far more than is needed does not damage the boiler. I remember an occasion when a five-litre bottle was put in (at my request) by an engineer that serviced the boiler, even though there are only three radiators. It did not seem to do any harm and he seemed to be quite unfazed by it. Thanks again, everyone!
L.L.

 

[Madrab]

I wouldn't go overboard, there are multiple chemicals contained in inhibitor and there have been issues with some of the Grundfos ERP pumps where it has been suspected that inhibitors were the issues, when the pump seals went on brand new units in some boilers

My understanding is the jury's still out as ScaleMaster are working with Grundfos on the issue I believe.

 

[Agile]

The bottles of inhibitor state the dosage recommended.

Usually about 1 litre per 80 litres of system volume.

But it is not at all critical.

 

[Lucky Luke]

Thanks, Agile, that's very useful to know. However, I have no idea of the volume of our C.H. system.
L.L.

 

[ianmcd]

I remember an occasion when a five-litre bottle was put in

You mean a gallon container , not a bottle ? 1 single bottle will be more than enough 1L, too much inhibitor can damage some boilers

 

[Lucky Luke]

Yes Ian, it was five litres. Thanks for the warning.
L.L.