Central Heating - Additive

[First-time-buyer]

Not long ago, we moved into the house and had the central heating system filled back up by a plumber. We asked if they could come back and put in some additive (Fernox F1 etc).

Anyhow...weeks...months later were still waiting and its time to do it ourselves. I have checked the FAQ in this section, and I does not have the answer.

I have Fernox F1 & Fernox F5 which can be filled via the cold filling loop. I was going to put the F5 in for 3-4 weeks, then drain the system down..flush through and then put in the F1...

The question....

I assume that Fernox F5 is the newer version of Fernox F3...as I could not find Fernox F3 in a cold-filling-loop bottle.

I did not really want to remove a bleed valve and pour in using a jug/tea-pot...

 

[ALEC1]

If it's a poorly designed open vented system it may have a benefit, otherwise save your money... A complete gimmick on sealed systems with a filter, and on a combi a disaster waiting to happen...

 

[First-time-buyer]

The system is a Combi Boiler with No Filter. Suspect DHW Heat Exchanger is slightly blocked as had to reduce the flow to bring the temp back up.

Its plumbed with 20mm & 15mm, so just something to work on that really...instead of replacing it.