Question regarding bleeding radiators

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Hi, I've not had much dealing with bleeding radiators before, so I’m sorry if this is a bit of a silly question :dunno:

I have lived in a new build house for about a year and half now, i decided today i would give the radiators and the heated towel rails.

The 2 radiators furthest away from the boiler let a good bit of air out before water come out and the rest didn't seem to have air in, the issue I’m confused about though is out of the other radiators that didn't have air in, all apart from 3 let clear water out, the 3 that didn't let clear water out let what appeared to be black water out, the strange thing is, the 3 that let black water wouldn't come from the nozzle that the air / liquid is supposed to come out of, it all seemed to spurt from what seems like a little behind the nut that you loosen, I’m not sure if this black water is a little too thick and that’s why it can't get through to the normal nozzle?

All the radiators that bled with clear water all come through the outlet nozzle fine.

Because i wasn't too sure what best to do, i just tightened radiators with black water back up as they were spurting everywhere a bit and not just tricking down, should i just have let it carry on coming out but kept an old towel around it to soak it up and eventually it would turn clear and start coming out of the outlet nozzle?

Also, if i did just need to let the black water to run until it was clear, what if that made a lot of water come out, does the boiler just replace this lost water the next time it is run?

The boiler i have is a Potterton Promax Ultra 40 Combi.

Thank you

James
 
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In theory, the colour of the water should be the same in all the radiators, as it's the same water getting moved around the system - as such, I can't comment on that, but you can't let the water run until it comes clear, as you'd just be emptying the system.

The system is a sealed, and if you empty water out when bleeding the rads, then you have to let more back in via the filling loop, normally found underneath the boiler. Check the pressure gauge on the boiler, and make sure it's over 0.5 bar.
 
It sounds to me like you are actually undoing the nut that holds the vent into the rad and not the vent plug itself!
Sometimes (especially if not tightened enough when installed) using a vent key to undo the plug will result in the male iron (nut) being wound out of the rad - resulting in air/water escaping from there! You will need to hold the ‘nut’ still with a Spanner whilst undoing the vent plug with a key.
 
Hi, thanks for the replies, it sounds like it may have been me undoing the nut when trying to loosen the vent, next time they need doing I’ll bare that in mind.

In regards to my original post, i realised i had actually missed the towel rail in the bathroom on the top floor (it’s a 3 story house), reason being is the rail was so high up i had to get step ladders to do that one, which i have just done, i had noticed this towel rail was only luke warm on the bottom half and cold on the top half, when i bled it air come out for around a 30 seconds before any water did, it felt like a long time anyway.

After doing this the boiler did say low pressure on it, it was now showing as 0.8 bar, i re-pressurised to 1.5 bar and have now put the heating on everything seems fine apart from the rail in the mentioned above now does heat at a balanced level from top to bottom but was still only warm to touch even though it was on full, the other 2 towel rails on the floor below are boiling and can only touch them for a few seconds before it feels too hot, the towel rail on the top floor that had lots of air in was like this when used last winter, i always remember it also being boiling to touch as well, because i have just re-pressurised or because i have only just let all the air out, could that be why it’s not getting boiling or could there be an issue? Is there anything i can do or look for as to why it is only feeling warmish but not boiling when the others towel rails are boiling?
 
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Hold the supply and return pipes - flow and return. If they are hot but the radiator not, then the TRV valve might be stuck, make sure the return valve is fully open, you can actually unscrew the head safely. If they are both hot, then its likely to be a blockage in the radiator, it might even have a baffle and be installed incorrectly.

Towel radiators normally attract air, because they are the highest point in the system.
 
T/R shouldn’t have a TRV on it, just manual valves... lockshield should be non-tamper. Top one may have crud in it.
Shut other rads off and focus all pump pressure on that T/R to see if you can get it too-hot-to-touch, then adjust other rads T/Rs so they don’t steal heat from it.
 
i checked the inlet and outlet pipes of the towel rail, i assume the inlet is the one on the left and the outlet is the one on the right with the dial to change the temp?

the left side was boiling hot and the right side was only luke warm.
 
Open up the TRV valve on the RH side, or take the top off and press the pin up and down a few times.
 
Nope. Wasn’t looking for that phrase. :p

Well you should have been ! Far more succinct than your

"Photos would have saved a few hundred words at least " seven words instead of ten and conveyed the same thought although a little more betterer
 

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