Upstairs radiators won't fill up after draining

[JohnD]

if you feel brave (you might get a leak or burst) you can briefly connect the incoming mains supply to the vent pipe, and see if it blows the blockage out. Often, however, it will be a very hard combination of limescale and magnetite, that will not shift. I have never worked on plumbing in a soft water area.

see FAQ 12 //www.diynot.com/forums/plumbing/boiler-central-heating-faqs.175736/
but there will probably not be a carp in your F&E tank.

It is almost certain to be where the 15mm pipe from the F&E tank joins the larger circulating pipes, often in the airing cupboard. If you hold a magnet against the copper pipes, it will be attracted to the spot where the mass of magnetite has collected.

Bale all the mud out of the F&E tank first, and tie up the ball cock float. This will reduce the amount of dirty water that comes down when you cut the pipe.

You will not be able to solder the wet pipes, so use compression joints to re-make the section you cut out. These will also make it much easier if it ever happens again. Use cleaning chemicals afterwards.

 

[nfollows1982]

Hi,

Just wanted to provide a quick update and also add some additional info to the OP.

When I drained the system I couldn’t get in the loft to tie up the ball cock and (ridicule expected) didn’t realise for about 2 hours that I had to turn off the mains supply to stop the tank from filling.

Whilst the mains was still on and I had the hose connected to the system, water continued to flow out until I turned off the mains.

If I understand correctly, the blocked cold feed would mean that the F&E tank couldn’t get water from the tank to the pipework, so would the continued flow of water whilst the mains was on point to the cold feed not being blocked?

The symptom I got whilst this was happening was a steady flow of water flowing out, then a trickle, followed by a cough and a splutter, followed by a steady flow of water.

I don’t want anyone to think I’m ignoring the advice given, just realised I’d not mentioned that and thought it might be relevant.

Someone else suggested that it could be air, and advised me to turn all rads off except the one closest to the pump and try again.

I’ve done this earlier and sounding like a whoosh as the water flowed through the pump and straight into this rad – although the flow pipe/valve was very hot the rad only got luke warm at the top and the left hand side so it didn’t warm up fully. The bottom was cold and the flow of water didn’t reach the return.

Does any of the above change anyone’s opinions/advice given thus far?

 

[JohnD]

would the continued flow of water whilst the mains was on point to the cold feed not being blocked?

Yes.

In which case, repeated bleeding at all points, and time, and sometimes turning the pump on and off, may clear any air bubble from a pipe. If the air goes into a rad you can bleed it out.

As long as there is no air in the pump, you can also turn off all radiators that seem to have flow, and the pump may then push the bubble along.

 

[nfollows1982]

As long as there is no air in the pump, you can also turn off all radiators that seem to have flow, and the pump may then push the bubble along.

So at the moment I've got the all othe rads ff barring one, which I did manage to get a bit of air out earlier so the air must have been pushed through a bit further than it had done before.

I take it you don't mean turning off all the rads?

Switching the pump on and off, would that just be switching to 1 then to 3 and keep repeating?

 

[JohnD]

air bubbles sometimes rise out on their own over time. Sometimes if you keep the pump running it will push a bubble into a place that it will not move from, and turning the pump off will let it get out. Sometimes turning the pump on will push a bubble out of the pipe. So if you are DIYing, turning the pump on and off for a few minutes each will sometimes help.

Another approach is to fill it from the bottom, using a hose on a drain cock, or connected to a radiator valve (garden hose screw connectors may fit the valves)

Yes, I did mean turn all the other rads off if they seem to have flow through them, but leave open the one with no flow..

To turn off the pump, set the room stat to a temperature that is lower than the room.

Bear in mind that if there was a lot of mud in the F&E tank, it may have moved down into the pipes and caused a partial or complete sediment blockage. That's why I recommended baling out the mud first.

 

[nfollows1982]

There's no flow through any of the other radiators.

Until I turned them all off barring the one closest to the pump, there was no flow through that one either.

With all the rads open and the system on, the flow reached the closest rad to the pump as far as the inlet valve but went no further.

There was no heat reaching any of the other rads on the system.

It wasn't until I turned them all off bar 1 that I managed to get flow into the first radiator.

If we are ruling out blocked feed and putting this down to air, would a redrain and backfill help?

This time I can get the the F&E so can tie it up properly and make sure it does empty.

If I backfill, do I do this with the ballcock still tied up and stop as soon as water enters the tank, then release the ballcock?

 

[JohnD]

if you backfill, tie up the float, leave it tied up until water has flowed into the F&E tank. The pressure of the hose is likely to push air out as the water rises.

before doing that, though, try bleeding all the radiators again, and try opening them one at a time and running the pump.

Keep bleeding the pump, it is odd that there is no flow anywhere if the pump is full of water. If the pump goes very hot, it is either jammed or dry. Have you verified that you can spin the pump spindle with a screwdriver, after taking out the central screw? There should be a few drips of water when you take the screw out. It will not gush.

Overnight, open all the valves and leave the pump off, perhaps the air will escape on its own.

 

[kbdiy]

This might be worth trying. Firstly clean out the header tank as suggested above. Turn off all rads, boiler and pump and leave the ballcock and any motorised valves open so the system can fill. Working one rad at a time, disconnect the flow and run it into a bucket to ensure you are getting a good supply. Do the same on the return pipe. If flows look good reconnect to rad, bleed it to make sure it is full. Then do the same to each rad in turn, working from downstairs to upstairs and away from the boiler. Any reduced flows will indicate a possible blockage or airlock.

Back-filling with a hose using mains pressure may also help to clear the problem - you may need to be a little inventive with connectors to the rad valves.

Although you may be able to push an air bubble round as suggested above, I have never had much success in doing so and it could be that your earlier exploits have shifted a blockage or air around the system. The bucket test should enable you to determine if there is a blockage at a certain point preventing you from refilling effectively.

Hope that helps.

 

[nfollows1982]

I keep checking the pump for air each time I've turned the system on but it's definitely got water coming out.

I haven't checked the spindle, as soon as I saw water from the central screw I closed it - didn't realise I could get away with removing it to have a look.

If I decide to a drain down and then backfill, with the rads downstairs being dropfed and needing draining one at a time, could I get away with draining the one downstairs rad with the drain point on (which would then do upstairs) and leaving the 3 remaining rads filled with water?

 

[JohnD]

I suppose it depends where the air bubble is (assuming that's the problem)

you could give it a try if it saves time.

 

[nfollows1982]

Here's the latest.........

So I drained down all of upstairs and for time saving purposes left the drop fed rads alone downstairs apart from the one a drained from.

Did this with the ballcock tied up and went back up and confirmed the tank had drained.

I then backfilled and bled each rad upstairs until the air had gone and the same with the pump, untied the ballcock and F&E filled up.

Turned on boiler and have now got all 3 rads upstairs hot but nothing downstairs.

I've turned the LSV's down on the upstairs and still nothing is coming downstairs.

The boiler is also shutting off after a period which I guess is due to the temperature of the water at the boiler?

I've found the where the pipes drop down and then branch off to the downstairs rads and the flow pipe is hot up to the tee and then maybe an inch further but the hot water isn't reaching the rads off that pipework.

What now? Shall I try shouting at them?

 

[nfollows1982]

Update 2......

Turned on again this morning and the boiler fired up for about 3 minutes and some heat in upstairs rads but then boiler shuts off and just leaves the pump running.

Flow to pump is hot, pump us hot and pipe leaving the pump is hot.

Put screwdriver to pump and I can hear it working, well think I can anyway.

Is there anything else I can try before I admit defeat and call in the professionals?

Thanks

 

[Whitling2k]

Is it something as simple as an auto-air vent? Do you have something that looks like a bike valve on the top of your boiler?

If you suspect a plug of gunge is moving around the system - you could try flushing the system? I did it recently to a house with 20+ rads and it was the single most effective thing I have ever done! I put a brief write-up here //www.diynot.com/diy/threads/blocked-heating-pipe.413091/ which might help.

I think that if you have only a few rads, 30m of hose-pipe, some spare in-line compression joints and an outsite tap with a quick release hose connector, it will only take a couple of hours to be completely finished.

 

[nfollows1982]

Morning,

So last night I thought I’d give it another go so before I touched anything I just fired up the boiler to see what happened.

On the lowest temperature setting, the boiler ran for maybe 5 mins and then shut down.

I checked the pipework at the top of the boiler which was hot, the flow into the pump which was hot, as was the pump body and maybe a foot of pipework after the pump.

Checked all rads upstairs and downstairs and they were all filled, no air came out same with the pump.

Someone else suggested I try to drain with the mains water on so the system would keep filling in a loop, so I thought why not! This time I used the drain point on the boiler, which as soon as I opened it there was an initial whoosh of water out the hose, followed by a steady stream but eventually the water ran out!

I thought that with the mains still on, I’d just be pulling new water through the system but I’d ended up emptying all the upstairs rads again – which I didn’t think was a good sign!

Turned off the drain and tried to fill the rads from the F&E, got a small spurt of air followed by nothing – started to think blocked cold feed again.

I turned the drain back on and there was a small trickle until I put a separate drain on the flow of the kitchen rad and there was a sudden whoosh of water through the drain on the boiler and the flow was far better than the last time, I could actually hear the water rushing into the boiler.

So off went the drain, back upstairs, and the rads hissed like crazy and one by one filled back up from the F&E tank.

At this stage the system was in this state: rads had filled from F&E, all the rads had been bled, the pump had been bled.

At first I thought I’d try to get the flow to the furthest rad so closed all the others off – nothing, not a thing. Went back to the rad in the same room as the pump and with everything else shut off even that wasn’t getting hot.

I sat and turned the pump off and on to 3 for about 10 mins and finally got one single radiator hot – then I just gave up because it wouldn’t flow anywhere else. Did a quick fire up this morning and, as above, boiler fired for a couple of minutes and pipework up to, including and a foot passed the pump hot – everything else cold.

Is there anything that is pointing to the pump being knackered? That seems to be the one thing that has been a constant in everything I’ve tried and everything else I’ve tried, draining, filling, draining, filling, getting air out etc etc just hasn’t made a difference – I’m thinking if it’s the pump, I could be doing this until Christmas and the water is never going to go anywhere!!

 

[JohnD]

I suppose you could give this technique a try. Might help if it is truly an air bubble. Also try holding a magnet against all the copper pipes and joints or elbows you can see in case it is a blockage. BTW you can run the pump with the boiler stat turned to Low or "0"

if you feel brave (you might get a leak or burst) you can briefly connect the incoming mains supply to the vent pipe, and see if it blows the blockage out. Often, however, it will be a very hard combination of limescale and magnetite, that will not shift. I have never worked on plumbing in a soft water area.

see FAQ 12 //www.diynot.com/forums/plumbing/boiler-central-heating-faqs.175736/
but there will probably not be a carp in your F&E tank.

It is almost certain to be where the 15mm pipe from the F&E tank joins the larger circulating pipes, often in the airing cupboard. If you hold a magnet against the copper pipes, it will be attracted to the spot where the mass of magnetite has collected.

Bale all the mud out of the F&E tank first, and tie up the ball cock float. This will reduce the amount of dirty water that comes down when you cut the pipe.

You will not be able to solder the wet pipes, so use compression joints to re-make the section you cut out. These will also make it much easier if it ever happens again. Use cleaning chemicals afterwards.

The pump will (should) have pump valves on each side (they might be seized) so you can take it out and look for blockage in it,