Applying FERNOX F4 Superconcentrate via airvent - problem!!

[Adrian13]

Hi All,

New member here

Understand per vokera call out guy that my drop in combi central heating pressure is due to potential leakage. The leak must be small as top up approx 1 every 6 weeks or so. When off pressure drops to approx 0.5 bar and when heating on raises to approx 1.0 bar, and higher if temperature is turned up, but always drops off when heating is off.

Ok, so tried applying the f4 as a possible solution as a potential leak is not visible. Note I am comfortable with removing radiators for decorating etc, and draining/refilling/bleeding etc.

Followed the instructions:
- both valves off
- remove air vent pin
- attached product hose and fitted to mastic gun

When ready to apply the F4 was stated to re-open one valve, did so, and received blow back via the mastic gun. Turned the valve down to reduce any water flow but was unable to force any F4 into the radiator via mastic gun, just wouldn't shift.

To me, possibly need to drain some water from system to reduce pressure, however had turned system off and allowed to cool down, pressure would have been approx 0.7/0.8 bar.

Any guidance or previous experience will be appreciated to help complete this process.

Thanks to all and Happy New Year.

 

[Burnerman]

Completely depressurise the system and open another radiator bleed valve. Have an assistant collect the water that exits from there as you pump the sealant in.
Close off all bleed valves, open rad ones, repressurise system via the filling loop.
John

 

[twgas]

connect the tube to the filling loop and pump it in there, if it's not a filling loop integral to boiler.

 

[Adrian13]

John , Mick,

Many thanks for your respective responses, they're much appreciated.

I suspected needing to de-pressure further to complete this job. Can you confirm de-pressurising is best performed via system being off and opening the external release valve and allowing the water to flow away?

Mick - your suggestion - the filler loop is not integral, simply loops below the boiler. For this approach do I also need to de-pressurise?

Thanks again guys.

Adrian

 

[Burnerman]

Just bleed water away from a rad valve until the pressure goes.....it takes a while but its the simplest and least invasive way.
Which ever way you choose, there must be no pressure in the system. If there is, you'll get an eyeful of radiator water when you break in!
John

 

[BingoBongo]

Second vote for putting it in filling loop