I think I have an airlock in my CH. I've just replaced pipes to radiators. Had a leak in microbore in concrete floor, so replaced all pipes by placing in loft - it's a bungalow. Gravity fed system and worried header tank may now not be high enough. bled radiators, but obviously they are no longer the highest points in the network. At best pipe network is flat, but in reality it isnt. Added an additional vent at a high point. Opened a couple of joints (push fit) that let air out, but still have water not circulating. And ideas?
Airlock in CH system
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Interesting occurrence. Just had leak from my vent pipe so clearly there is enough pressure(?) to push water round the system, or at least into the system but it chose the vent pipe rather than circulating/ sucking in from the return loop. At least the water was hot! Just a set loft now. Topped up and switching it on again. Have put a stopper on the vent pipe for now.
Do not put a stopper on the vent pipe, clue is in the name
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Thanks. All seems to have sorted itself out. I have left a stopper on the vent pipe. But am convinced I didn't need to have put in a vent pipe in the first place. The boiler may have a built in vent? Anyhow all working for a couple of weeks now, so very happy. Thanks for advice.
Don't leave a stopper on the vent pipe!!
As @ianmcd says, it is a vent pipe and needs to be able to vent. It is a safety device worked into an open vented CH system that releases excess pressure if the system overheats and it needs to be open!
You need to fix the circulation/air lock problem rather than circumventing the system's safety devices. The boiler will not have a built in vent, it may have an AAV but that's just to release air that finds its way into the boiler.
As @ianmcd says, it is a vent pipe and needs to be able to vent. It is a safety device worked into an open vented CH system that releases excess pressure if the system overheats and it needs to be open!
You need to fix the circulation/air lock problem rather than circumventing the system's safety devices. The boiler will not have a built in vent, it may have an AAV but that's just to release air that finds its way into the boiler.
It is only a vent pipe because I added a pipe into the network because I thought I may need to let air out from the highest point in the loop. It's just a vertical pipe. The original pipe run was in the floor, so I guess never needed it. Do I actually need it and should it then just simply loop back to infill tanl/overflow, just in case the system just pumps water through the vent pipe (as least course of resistance) as it did when I started the system up?
Today must be wind up Thursday.
Andy
Andy
Try looking at a few gravity fed diagrams mate... You might learn something.
Clue: what happens to water when it's heated?!
Then do us a sketch of how your system is, because I think this is a seat and steering wheel problem, but I'll give you the benefit.
You said in your OP that it's a gravity fed system with a header tank. To the professionals on here that tells us that it's probably an open vented ch system that will have a vent pipe that runs up to the f&e cistern in the loft and curves over the top of it and points down into it. Is that what you have? Is it that pipe that has water coming out of it?
You may also have an open vented HW cylinder that does the same into the main cistern in the attic.
You may also have an open vented HW cylinder that does the same into the main cistern in the attic.
Have come across a few where the feed does both jobs 
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