Central Heating Inhibitor

[planemad]

How often should the inhibitor be changed in a combi system.
I'm currently using Fernox F1 which has been in for one year.

When it does get to the time to change the inhibitor do I drain down 100% then refill with fresh water adding fresh inhibitor.

or do I just add the inhibitor into the existing water using the rad valve.

Thanks

 

[spm8]

you should not need to change it if u have not had to keep topping boiler up or you have drained it down .you can buy test kits which tell u strength in system

 

[ChrisR]

If you're not losing anything much, once in several years would cover you.