Adding corrosion inhibitor

[Beeg]

Hi all, DIYer after some advice. I’ve drained my CH system (combi boiler) to replace a couple of radiators.
The new rads have been fitted and I’ve been trying to add inhibitor to the system. I’ve isolated both valves on the radiator, opened the vent and removed the plug. I have a flexible funnel which I’ve been pouring the inhibitor through; however whenever I pour it in, it comes straight back out the top of the radiator where I am pouring it in. I have tried on 4 different radiators now and have the same problem on all of them. Unfortunately I don’t have any towel radiators which I can use. Any advice greatly appreciated so that I can get my heating and hot water back.

Many Thanks in advance.

 

[steadyon]

1. You'll have to remove as much water from the radiator as the amount of inhibitor you want to add.
2. Shutting the valves doesn't empty the radiator. It's still full of water.
3. Syphoning the water out with a bit of rubber / polythene tubing is how I do it, but I don't suppose its the HSE approved method! Spit the water out ASAP.

 

[gmartine]

Try a fitting a rad valve with drain off, you can isolate as well as drain down the rad. Removes the faff when adding inhibitor that way.

 

[SJB060685]

With both valves closed and no water in the radiator remove the bleed vent and other blanking port on top of other side and try again. You need somewhere for the air to escape from as its displaced by the inhibitor.

 

[Beeg]

Thanks for all the replies, managed to sort it in the end - it was as simple as holding a cloth around the blanking plug as I was pouring it in....

Just out of curiosity, I understand that the HW should not be used if the CH is drained in a pressurised combi system - can anybody enlighten me as to the technical reason behind this?

thanks again

 

[SJB060685]

If the CH side was drained then your low pressure switch will cut power to the PCB. Water will flow from the taps but safely devices will prevent the burner from firing.

 

[Ric2013]

To add to SJB's explanation, a combi boiler needs primary water (the sealed system) to circulate between its heat exchanger and the secondary internal heat exchanger that heats the HW. If the CH side were drained, you'd be effectively running the boiler dry, hence the need for safety devices.

 

[MARTIN STANJER]

Hi all, DIYer after some advice. I’ve drained my CH system (combi boiler) to replace a couple of radiators.
The new rads have been fitted and I’ve been trying to add inhibitor to the system. I’ve isolated both valves on the radiator, opened the vent and removed the plug. I have a flexible funnel which I’ve been pouring the inhibitor through; however whenever I pour it in, it comes straight back out the top of the radiator where I am pouring it in. I have tried on 4 different radiators now and have the same problem on all of them. Unfortunately I don’t have any towel radiators which I can use. Any advice greatly appreciated so that I can get my heating and hot water back.

Many Thanks in advance.

It sounds like you are pouring it in too fast. It needs to go into the rad in a very small stream so that air in the radiator can get out through the funnel at the same time. Try removing the blanking plug at the other top end of the rad to let air out as the inhibitor goes in. I use a half inch male to compression fitting screwed into the end of the rad with a short bent piece of 15mm copper pipe rotated upwards, and away from the wall. I put a small funnel in the end of that. Slowly does it. I put an o ring on the outside of the male fitting to prevent leakage when it's screwed into the rad without having to do it up tight (you could just use just a few turns of ptfe tape). You will probably always loose a small amount when removing whatever fitting you have used when you have finished, so watch out for spillage then too.

 

[MARTIN STANJER]

It sounds like you are pouring it in too fast. It needs to go into the rad in a very small stream so that air in the radiator can get out through the funnel at the same time. Try removing the blanking plug at the other top end of the rad to let air out as the inhibitor goes in. I use a half inch male to compression fitting screwed into the end of the rad with a short bent piece of 15mm copper pipe rotated upwards, and away from the wall. I put a small funnel in the end of that. Slowly does it. I put an o ring on the outside of the male fitting to prevent leakage when it's screwed into the rad without having to do it up tight (you could just use just a few turns of ptfe tape). You will probably always loose a small amount when removing whatever fitting you have used when you have finished, so watch out for spillage then too.

Hi all, DIYer after some advice. I’ve drained my CH system (combi boiler) to replace a couple of radiators.
The new rads have been fitted and I’ve been trying to add inhibitor to the system. I’ve isolated both valves on the radiator, opened the vent and removed the plug. I have a flexible funnel which I’ve been pouring the inhibitor through; however whenever I pour it in, it comes straight back out the top of the radiator where I am pouring it in. I have tried on 4 different radiators now and have the same problem on all of them. Unfortunately I don’t have any towel radiators which I can use. Any advice greatly appreciated so that I can get my heating and hot water back.

Many Thanks in advance.

Just noticed you've got it sorted already. Glad to hear it!

 

[Beeg]

Thanks everyone for taking the time to reply - great to see professionals willing to give helpful advice to DIYers. Thanks also for the explanation on the workings of a combi boiler and why you shouldn’t run the HW with the CH drained.
I did read that isolating the heating circuit supply / return at the boiler and repressurising the boiler will still allow (safe) use of the hot water - is this true or is it best to just power down the boiler whenever the heating is drained?
Regards
Beeg

 

[SJB060685]

Thanks everyone for taking the time to reply - great to see professionals willing to give helpful advice to DIYers. Thanks also for the explanation on the workings of a combi boiler and why you shouldn’t run the HW with the CH drained.
I did read that isolating the heating circuit supply / return at the boiler and repressurising the boiler will still allow (safe) use of the hot water - is this true or is it best to just power down the boiler whenever the heating is drained?
Regards
Beeg

Yes if possible to isolate the flow and return leaving the boiler you could drain the heating circuit whilst still having a boiler circuit, which would allow you to continue using HW.

You said above "you shouldn't run the HW with CH drained". As I said above if the boiler is not pressurised (filled) then safety devices will prevent the burner firing, it's not a case of shouldn't but rather can't, unless of course something has failed.

 

[Beeg]

Yes if possible to isolate the flow and return leaving the boiler you could drain the heating circuit whilst still having a boiler circuit, which would allow you to continue using HW.

You said above "you shouldn't run the HW with CH drained". As I said above if the boiler is not pressurised (filled) then safety devices will prevent the burner firing, it's not a case of shouldn't but rather can't, unless of course something has failed.

Thanks again! 😀
Regards
Beeg