I've just drilled through a pipe under the floorboards :-( It's one of the 22mm pipes between the condensing (not combi) boiler and the hot water cistern. I've fixed it and bled (bleeded?) the pump. The boiler starts normally but then goes off after about a minute without heating the water.
I'm assuming water is coming from the loft header tank because air and then black water came out of the pump when I bled it. There isn't any air in the upstairs radiators.
Any ideas?
I presume this is conventional (or should I now be saying traditional?) system with a small heating header tank in the loft. You very like have an air lock. This may in part be due to a blockage where the feed pipe joins the primary circuit. If you could get a picture of the general arrangement of the pump and pipes I might be a lot more specific.
A fairly common gotcha to check is whether there's an air bleed valve at a high point in the pipework, probably near the hot water cylinder (not "cistern"). If this is full of air it can stop circulation.
Came across a big old system recently where a couple of rads weren't heating up. Tracing their pipework (using my X-ray vision[1] since they were hidden in skirting trunking) I found they were connected across the primary coil on the HW cylinder! The pipework branching to the rads was on a high point with an automatic air bleed valve and the branch was cold. Percussive therapy failed to free the AAV so I loosened it to let the air out and presto - hot rads!
Love the sig.. Listening to Brothers in Arms whilst scanning through.
Strictly bodgerama, but it works for me. Turn off every rad except one and set the boiler going. After 10 mins open another rad and shut the first one, repeat this all over the house bleeding as you go - one open rad only.
I assume that directing the full force of the pump into one particular part of the circuit is more effective in flushing air bubbles forward into locations where they can be successfully bled off.
Happened twice to me. Attach a hose to the c/h overflow pipe (other end to mains water) and run mains water through.
2 minutes and lotsa bubbles in the header tank later, problem solved. P
I think you mean the vent, not overflow, pipe!
To be clear what the problem is, IME an airlock results in radiators not bleeding: you can take the bleed screw right out but after a point no more air comes out but no water comes out, so the rad(s) doesn't/don't fill. The OP says there isn't any air in the upstairs radiators which I assume means they've bled and are now full of water, but he's getting no circulation.
Another thing he could check is whether there's an automatic air bleed valve on top of, or possibly inside the boiler, and whether the cap is loose and air hisses out when the system is filled.
This works well unless the problem is air in the pump itself.
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