Peaklander

Yes 28mm around the bottom of the H on the boiler flow to pump and 22 up to vent with 15 down. i don’t know how long it has been since a drain-down or what chemicals have ever been in.

Yes got one.

Hi, here's the update. We cut the H pipework out, releasing it on the top side of the pump inlet valve. Popped a hosepipe below the cold feed isolating valve and emptied and cleared the header. There was plenty of gunk just in that, obviously most sitting on the bottom and sides under the water level. The inlet side of the pump was choked though. I don't have a pic of the H pipe as I was in the loft but that did have residue on the pipe walls. After this was re-instated the partial refill that was needed seemed to go better than previosuly and there was no pump-over at PP2 pump setting but still a little at full bore. So I asked plumber to lift the vent which he did. I'd already told him that I didn't want to retro-fit a pressurisation vessel. There was no pump-over after that at CC3 but in fact I left it at PP2 and all was well. The header had got some brown water in again from that brief pump-over and so I'm resigned to another full drain and flush/fill - but not until the summer. It has some Fernox P3 in for now. I need to leave it and give my parents relief from the to-ing and fro-ing. Thanks again guys for your sage advice and comments. It has been very helpful and gave me confidence to stand my ground and not do the pressurisation and certainly not rip the whole lot out and replace for £5k

A quick question, if you were me, would you still replace / inspect if possible, the H pipework? I don't think I now need to introduce the pressure vessel in place of the header. I'm planning to lift the vent pipe U and drain / refill after cleaning the header.

Plumbers 2 & 3 did. Don't know about #1. Thank you for all the help. This thread proves that often all of the detail is needed before a cause can be found.

Yes well it wasn't me it was Plumber #1 that said to swap the pump and sometimes I do listen. It can be a fine line to tread when a DIYer interacts with a tradesman. 😊

I didn't try it earlier because I was distracted by my Dad. Later I felt that maybe PP1 will be too slow and I can't be there to check over the next few hours. So I have come home to go to a 50th wedding. It will be good now until Tuesday when I am going to be steered by what Plumber #2 wants to do. However it could be as simple as lowering the water level. I did bend the float arm but couldn't bail any out as that's when Dad felt odd and I had to check for stroke and heart (I am not a medic). Also there is scope for the vent to be raised. Maybe that's all we end-up doing on Tuesday.

Yes the yellow leds flash on those variable speed modes - just needed to catch it right with the phone otherwise they are OFF! I haven't gone to PP1. I will leave until Tuesday and I suspect that Plumber #2 will want to remove the tank as I said. I think I can risk that. Screwfix have the parts ready for me to pick-up. My job will be to bail-out the header although as it's circulating around anyway, perhaps I can let most drain out first and then bung it up.

Ok some pics plus my father is having some sort of issue which I’m keeping an eye on. This is the first setting and the water flow over. This is PP2 with reduced water that sounds worse than it is. That just means I should have looked and not listened. There is scope to lift the height of the vent. Edit. Obviously the water colour is still not good and it will need a further clean.

I changed the pump and I will double-check the valves when I go there this morning. Plumber #2 says that they are very fragile, having sat there for years and they can break when operated.

Sorry about not mentioning the "few cm" before - it's been on my mind and I sat there this morning scratching my head and thought about it again when I saw your reference to 2m. I will go to the house in an hour or so (need to give my parents enough time to get up and going) and post a photo. I can obviously bend the float arm down a bit, in order to lower the water level. The tank is pushed tight against low rafters and there's not much scope to lift the bend on the vent. It must have been a finely balanced set-up and then I came along and changed the pump. Rather than go your combined feed/vent @John Carroll, Plumber #2 wants to remove the header and set-up an expansion vessel with PRV and fill loop. We have discussed it and will do it as long as we just set a very low pressure. I don't want to find any leaks in the pipework. He will re-pipe the H anyway and the vessel will physically go in place of the header but I will examine that H cross-pipe to see what I can see. I'm starting to think that the sequence of events was: 1. Lack of corrosion inhibitor and no mag filter, caused some sludge and a little gas to be formed that probably turned into an airlock. This caused the boiler to constantly trip out and in, without getting the radiators to heat. 2. Air removed and pump changed and system cleaner and filter added. 3. System flushed, sludge removed and all ok except the pump over. 4. The new pump has highlighted the lack of tolerance there is with such a low vent to water level differential.

The vent pipe bends over just above the header tank. So it's just a few cm above the water level. I don't have a photo but there's not much room to accommodate a rise in the water level in the vent.

Yes but here the vent is behind the pump, on the other side of the cold feed tee, just along the horizontal pipe in the H. So a restriction there can divert but I’m not so sure of one further along the system. However we will see. I hope! Edit: just seen the comment by @marshian above. I don’t think it’s been happening for long but something caused the initial problem of air or airlock in the system and lukewarm rads. and that was before the pump change obviously.

We fitted a mag clean a few days after the pump. I cleaned it after a week and it did have some gunge and a few steel flecks. The HE isn’t having any trouble keeping the CH plenty warm enough throughout the day. As for restrictions, I can understand how one at the tee at the cold feed / H pipe can divert flow up the vent that’s just before it in the flow circuit but I can’t see how a restriction further round the system can do that.

Yes that's a good call. I had already looked at the link you sent a few days ago and I can see that they are available next day. So yes, that would be the next step.