How to bleed radiators?

[nameisme]

Hello all,
A couple of questions on this.
I have bled one radiator once and just used a flat head screw driver and then water came out which I caught in a bowl.
But at what point do you stop bleeding the radiator? when no more water comes out the radiator?
Do you do all the radiators at the same time?
Thanks all.

 

[Anon_E_Mouse]

You stop bleeding when water comes out. All you are doing is removing an air
Do downstairs radiators 1st ( although they rarely need bleeding) then upstairs.

 

[nameisme]

Ohh no I let a fair bit of water out my radiator a couple of weeks ago as I by accident left the valve slightly open on the boiler and the boiler pressure went way too high so I bled the radiator until the pressure on boiler came down to a nornal level. Do you think I will have caused any damaged by letting some water come out the radiator, probably was about a cup full of water.

 

[nameisme]

Literally water started to come out the radiator after just a few seconds of turning the bled valve open, Is this normal?

 

[Elkato531]

Perfectly normal. Releasing a bit of water from a rad to drop the pressure if its too high is fine.

 

[nameisme]

Perfectly normal. Releasing a bit of water from a rad to drop the pressure if its too high is fine.

Thanks, also wondering my bathroom has a towel radiator which looks like this, it has two nobs at the bottom. How do I bleed this radiator?

https://solairequartz.com/product/aura-25-curved-towel-warmer-central-heating-chrome-white/

Also when I bleed the radiators, do I need to do them all at the same time?

I saw a video on bleeding radiators and he said make sure the valves are open at the bottom of the radiators? Is this important to do or not? What valve is this? is the the valve that means the radiator is turned on, ie meaning open? When I bled one radiator which brought down the boiler pressure this particular radiator was turned off ie it does not get hot. But it still brought the boiler pressure down.

 

[ericmark]

Often bleeding is easy, open until air stops and water starts coming out. However some times we bleed to remove an air lock, then we bleed twice with only one valve open at a time, so it bleeds both the feed and return, normally when heating not running. There are levers to latch open motorised valves when bleeding if fitted.

Water has gases in it, and the colder the water is, the more gas it can hold, so when a system is first filled the gas in the water is released as the water warms up, so after it has run for first time often there is more gas to release, but once done second time there should not be a need for it to be done again until system is refilled.

Since we put inhibitor in the circulating water maybe should call it a coolant, we don't want to bleed more than necessary.

As to the TRV and lock shield valve, these need to be set to work efficiently. The TRV takes time to open and close, and the lock shield valve controls how fast the radiator heats up, if it heats up too fast the temperature will over shoot, also if open too much the return water will get too hot and the boiler will modulate (turn down flame height) too early so it will take longer to heat the house.

I am no plumber, I am an electrician, I am told plumbers have differential thermometers so they can set the in coming and out going water to have around 15°C difference. All I can do is turn off the lock shield and then ¼ turn at a time with around 2 minutes between each adjustment turn it on again until I feel a little warmth on the supply pipe.

I have electronic TRV heads so my computer shows target and current so I close the lock shield a tad if current over target, and if after a couple of hours target not reached, open the lock shield a tad, once set rarely need to touch.

Biggest problem with central heating is some one has fiddled with it, the heating engineer has set it all up A1, then some one fiddles with it. I came to mothers house and found every lock shield valve wide open, the result was it heated one room at a time, once a room was warm the TRV would close, and it would start heating next room, the boiler was actually cycling on/off as return water so hot but her bedroom was cold. I had to remove the tap tops and replace with covers to stop her fiddling.

Once set rooms were spot on, rather impressed on how well TRV heads do control room temperature when set correctly.

 

[Elkato531]

A very complex answer to a simple question there ericmark.

The valve at one end of the radiator should always be open. This is the lockshield valve at the opposite end to the valve you use to turn the rad on/off. When you open the bleed screw, the pressure is the system can then force more water into the rad and push out the air. For bleeding purposes, it shouldn't matter if the control side of the rad is open or closed.

The vent point for your towel rail will be at the top on either the left or right. It is usually at the very top of one of the side rails but on some it can be found just round the back.

Only bleed radiators if they are cold/cool at the top and hot further down. You don't have to do them all, just the ones that need it.

Bleeding rads will lower the pressure in a sealed system as you have found so always check the system pressure when you have finished and top up as necessary.

 

[nameisme]

Thanks all, thats the right word. I have a couple of radiators which I have isolated to save money on heating, can I still bleed the radiator while its still isolated or do I need to unisolate it first? I think Elkato said yes I can when he said "For bleeding purposes, it shouldn't matter if the control side of the rad is open or closed."

 

[nameisme]

Finally had time to bleed the radiators. So annoying as one if them where the radiator key doesn't work and the place where you put the flat head screw driver to turn it had no grip, please see pic. What do I do?

 

[nameisme]

Bleed key

 

[nameisme]

Don't understand why this key will not work?

 

[JohnD]

I think the old one is clogged with hard limescale.

you may as well take out that old plug (with a spanner) and fit a new one. They are not expensive. Usually sold in pairs, one plain plug and one with vent pin. Close the valves at both ends of the rad first.

the modern ones usually have a "O" ring seal but PTFE tape on the thread may also do some good. It looks like the one in your pic was badly fitted, and not repaired when it first leaked.

mine have this plastic shroud, and water squirts out of the little hole into your jar

Screwfix, Ebay etc. "radiator vent plugs"

keep a few in your plumbing box.

 

[CBW]

Those utility keys don’t always work. Either use a clock type, or as suggested, replace the bleed vent.

 

[nameisme]

Well I bought a bleed key and it worked, don't think that other one is a bleed key.

Is this correct that they are two Dials on the radiator one on the left one on the right one of them turns to radiator temperature up and down and also off , the other turns the radiator off and isolates it. Is it ok to bleed a radiator which is isolated?