Morning all, Just after your thoughts on a problem I have with a vented system and F&E tank. Drained the system the other day, had to connect a hozelock connection to the downstairs bathroom radiator as no drain valve, this drained that rad and upstairs. Then realised that the other downstairs rads must be dropfed so I had to drain these down separately. (Now the funny part, but might be relevant) I couldn’t get up in the loft to tie the ballcock up and didn’t realise that the mains water was feeding the F&E so I had a hose connected to the pipework downstairs for nearly 2 hours whilst water kept coming out, until I turned off the mains and hey-presto, no more water!! Whilst I was draining, and still had the water on, the water would flow and then cough and splutter and then flow really well again (again, not sure if relevant but worth mentioning). I had all the rads off, replaced all the TRV’s and LSV’s, hosed through all the rads, and then refitted everything. Turned mains back on and started to bleed downstairs and I got the downstairs rads filled with water – problem being that upstairs didn’t. I spent a couple of hours going back to the upstairs rads and they were all hissing air but I couldn’t get any water. I managed to get to the F&E and the ballcock is letting in water and that seems to be working fine. So I’ve connected the hose to the mains and pumped water back through the system and bled the upstairs rads and they are all filled with water now. Turned on the boiler and it fires up well and stays on, but none of the rads were getting hot, not even the pipes to them. So I’ve got the floorboards up and found the pump and found that the feed to the pump was hot, but the pipework out of the pump wasn’t. I’ve tried to bleed the pump, but there was no air so I gave it some gentle persuasion with a lump hammer and turned it up to 3. This resulted in the pipework after the pump to get hot too and it reached as far as the flow on the rad closest to the pump but it didn’t get any further. So that’s where I’ve got up to, any ideas, suggestions and potential ridicule welcome. Thanks
you have an air lock, the pump is not a pump, its a circulator, think of a bike chain the top can only go as fast as the bottom each link acts like the water in your pipes if theres one dissconnected the whole chain cannot work, thats whats happening in your pipes a gap of air is stopping the circualtion and the pump cannot shift it, Its a tricky job even for a plumber as there's no set method, every plumber will have a few idea's of his own and guessing where the airlock is , is the key to getting it out, a hose pipe and mains pressure is sometimes the best way, but where to put it is sometimes limited and might only short cut the airlock and fill the header, sometimes an airlock can move all by itself, you just gotta keep trying,
tom.plum, thanks for your speedy response. I understand the logic there with your description, I assume I've caused the airlock by having all the rads off etc? So where do I start? Is it logical to try and start again and drain the system off completely and refill?
What floor is the pump on - ground or upstairs? I haven't done this kind of job, but wonder if something to try would be to shut off all the valves on all the rads on the floor the pump is not on, and open fully all the valves on the same floor as the pump. Then try running the pump through just the rads on the same floor as the pump - 'cos I'm guessing that's where the main air block is? Run the pump on full for a minute, then turn it off and see if you can bleed these valves further - hopefully any shifted air would have stayed in the top of a rad. Repeat... If that doesn't work, try the exact opposite . On a different - tho' connected - note, don't forget to add 'additive' to your system when it's finally all up and running so's it's maintained.
"Is it logical to try and start again and drain the system off completely and refill?" I think I recall reading on here - it was probably from Mr Plum himself - that a good idea is to slowly refill using a hose on the lowest part of your system, back-filling until the F&E tank starts to fill. Emphasis is on slow fill. All rads fully open. Bleeding the rads as they fill - starting on the lower floor rads of course. One wee problem - you still don't have a drain spigot? That means you'd be filling from one side of an isolated rad so the pipe going to the other side of that rad will be dead = potential air block! If you do decide to drain down again, cut into a suitable pipe (low as possible and near an outside wall), fit a tee and a drain cock.
The pump is upstairs, directly above the boiler which is in the kitchen. So using your theory, to start with turn off the downstairs rads and see if I can get the air through the upstairs rads? In response to your other post, I have fitted a drain point to one of the downstairs radiators as this is what I connected to when I backfilled the upstairs rads on Sunday so I do have a point on the system to get water back in that way if needs be.
Cool. Yes. This is just theory of course, 'cos I haven't a scooby. But I'd assume that if the upstairs rads & pipes were clear - no air - then the pump would run fine and circulate as it should. So, no harm in trying that? Shut off all downstairs rads, fully open all upstairs, and try on full speed for a minute. (I'm also assuming that the pump itself has water in it as running them dry ain't good... Since the pipe either side becomes hot, I'm guessing that it does have water.) Don't forget to try bleeding all the rads after that minute - but shut off the pump first. If that fails, then try shutting off all the upstairs rads too, bar the end one, and trying again.
yes its all trial and error, you know the tanks filling cos the water did't stop on your original drain, If you have a zone valveor 2 zone valve make sure they're open when filling and venting, DO NOT RUN THE PUMP when filling venting, when water comes out of ever radiator bleed valve then run the pump, you'll hear the sound change asa the pump trys to clear the air, it will find a way out eventually, just keep trying differant things,
So as it stands at the moment, when I open the bleed valves on any radiator upstairs or downstairs, there is water and no air - same can be said of the pump, there's no air. So what you mean is, the air is somewhere in the pipework and it's really just trying to get it somewhere where it can be released (i.e. through the bleed valve when I get it in a rad)?
It'll either end up in a rad(s) or else escape up the F&E vent pipe. Have a careful look at all your CH pipework from the boiler and pump - any 'suspicious' angles or 'high' bits?! Can you identify where the highest part of actual CH pipework is? I don't mean the pipes going to the F&E tank, but the general CH pipework as it comes (and returns) to the boiler and the pump and the motorised valves, etc? If there is a suspicious bit of plumbing there, then you could always slice into it, fit a tee and have short ( a foot or so) vertical length of pipe with an air release thingy on top.
Just a quick update, as I managed to get home at lunch and try this out. So I turned off all the rads except the one in the same room as the pump, checked pump and rads for air and there wasn’t any. As soon as I fired up the boiler this time it sounded like a bit of a whoosh as the water went straight to this rad. Turned off boiler, bled again and released a bit of air. Turned back on and the hot water is definitely getting to the rad but it goes through the valve and then up the top of the rad and misses out the middle and the bottom, the temp of the rad is also nowhere near as hot as the flow pipe and the valve. I had the boiler running for about 5 mins and there was no increase in rad temp at the top and the rest of the rad didn’t get any heat. So progress in terms of the fact heat got to the rad, but where to next? Is it a case of lather, rinse, repeat?
the rad that you can feel heat at one side, shut both valves off, undo the side thats cold and attach a hose pipe, try 'pulling' the water through that pipe,
Remember your need to re-balance your system as well, once you have flow. My method for removing air locks depending on what rads you have is remove bleed valve on rad use a female coupler with hose attached, have both valves off and open one valve and let water and air gush out then close that valve and do the other,work your way round the system. Works every time for me.
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. 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. The boiler is also shutting off after a period which I guess is due to the temperature of the water at the boiler? What now? Shall I try shouting at them?
is there a balance valve on the hot water curcuit to the cylinder? if so shut that down, that will give the give the water nowhere to go only down stairs,
Nothing is getting hot again now, not even the 3 upstairs that were nice an hot a couple of hours ago. I'm tearing out what little hair I have left!!
One little trick I do which many plumbers would frown on is have the pump running remove bleed screw on pump then with a screw driver push it in pump to jam it,hold for a few seconds then let it go repeat this a few times job done.THATS NORMALLY A LAST RESORT!!
I think I'm getting close to the last resort. What are the potential implications of doing the above?
A bit of water,its not good practice to many but I was taught old school.GOODLUCK!! I expect someone will be along shortly to tell me about bad practice.
Mr Fellows. Can't comment on what p'boy suggests other than it shouldn't do your pump any harm as it's a brushless motor - ie: won't overheat the windings if it's stopped. Or shouldn't. Provided it does have water in it. If you try this, perhaps switch the boiler off so's you only have cold water going around. Something else you could try - you should keep a blog on all this - is; shut off both valves on every rad, drain down fully (I know, I know...), then back-fill very slowly (trickle) just the CH pipework - ie no rads at all. Once the F&E tank has half-filled from doing this, then try running the pump full-on with the boiler on a low setting just to see if you can get hot water flowing around just your CH pipes. (This assumes it has a by-pass on the end of the circuit - do you know if it does?) If it doesn't have a by-pass - ie: water won't flow without an open rad on the circuit - then fully open the end rad on one of your circuits first. If you do this, then allow that rad to fully fill and bleed first. If this works - you get a circulation on the first circuit - then shut off that end rad and open the end one on the other circuit and repeat.
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