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I moved into a new home and so inherited the existing central heating system. When the boiler is heating the water, there is no problem, but when it heats the radiators there is noise all over the house. The noise is a gurgling, gushing sound – not tapping like I’ve heard produced by other central heating systems. There is no leak.
I’ve already tried bleeding it and that isn’t the problem. All the radiators get hot. Any other (fixable) reasons why the system is noisy?
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It sounds like there’s air in the system. Go to each radiator in turn and use a radiator key to turn the bleed screw on the top until water flows. Use a towel and bucket of course.
Also check that the pressure is high enough. Check the manual but you usually need around 1.5 bar.
I presume we are talking about banging and gurgling noises.
you have air in the system get a radiator key and bleed from the lowest to highest point not forgetting that there is usually one on or near the hot water cylinder.
Sounds to me like you’ve got air in the heating system.
If you haven’t got one, purchase a radiator key from a hardware store, then..
Turn the heating on, make sure all of the radiator valves are open, so all of the radiators get hot.
Check all of the radiators, if one or more don’t get very hot then there is air in the radiator. To remove the air, or “bleed” the radiator do the following..
The bleed valve is locates at one end at the top of the radiator and is opened with the radiator key. With a cloth placed underneath the bleed valve, slowly open the valve with the radiator key. If there is no air in the radiator then water will come out. If there is air in the radiator then you will hear a hissing sound as the air is released from the radiator. Keep the valve open until all of the air escapes and water is coming out of the valve.
Repeat this process with all of the radiators that aren’t very hot. You may need to repeat this process once a week, or so, to make sure all of the air is removed from the heating system.
You may have air in it but it actually is likely to be the pump is too fast.
central heating pumps have 3 settings, controlled by a slotted screwdriver on the pump.
fidn this switch and turn it, making note of where it was. I bet you’ll find it was on its highest setting. Most houses cope with speed number 1 or 2, very few need the top speed.
I’ll take bets that this will quieten down the system for you.
The sound you describe is definitely air in the system. if it is a combi boiler, you have to bleed the system correctly. Switch off the boiler, and wait 10 minutes. Then bleed the first rad and check the water pressure on the boiler. It should be one or one and a half bar. Top up as needed. Then go to the next rad and do exactly the same procedure Check the boiler water pressure before going to the next rad. Then check the central heating pump. Unscrew the nut in the centre of the pump and any air that is trapped will bubble out. Switch the dboiler back on, and if the problem is still there, then you have air in the pipwork and you have to get a plumber to do this. Remember that when you vent air from the rads, to leave the vent open until the water runs freely with no hissing noise.
You should have automatic air vents, these have a plastic cap on top, a bit like the cap you get on car tyre valves, these should be left loose not tightened down to let air out. Some times depending on how the system is plumbed, you cannot always get all the air out of the rads.
You dont say what sort of system you have, but if you have a combi boiler, meaning you get hot water from the boiler, you need to make sure the pressure gauge is reading between 1.5 bar to 2 bar with the heating cold.
If you have a small tank in the loft, make sure the ball valve is not stuck up. There must be some water in the header tank.
Failing these, it could be the way your heating is plumbed, or it could be the circulating pump. If there are any speed settings, try a slower speed, except for a combi boiler which must be left at max speed.
It sounds very much to me that there is some rust or corosion in your radiators or pipes. This kind of thing happens when a house has not been used for a long time and nothing is done to correct it. I would call in a heating engineer.
you’ve got air traped in the system.
you have to find the highest rad in the system, upstairs if its a semi.the bleed them when the system has been running for an hour or so, be carefull the water is very hot slightly open the bleed valve on the rad with an old towel over it to catch the water do it a few time over the next few days
Probably has air in it and needs bleeding at the radiators with a small bled key which you can get cheaply from B&Q, a hardware shop or plumbers.