CH venting into header

[John Carroll]

58 minutes ago, marshian said:

OK so pump over can be reduced but even on lowest pump speed/pressure it's still there.

 

@John Carroll for the cheap seats just explain to me how lowering the water level in the F&E tank would help

 

Is it that you lower the level in the F&E Tank and as a result you lower the level in the vent pipe so potentially reduce the opportunity for pump over and you are effectively lowering the overall head - I'm struggling to get my head round it (also my F&E tank when system is running is a few mm below the overflow pipe)

Lowering the level in the cistern is the same as increasing the height of the vent pipe above the water level, if the present height of the vent (where it turns down) above the water level is say only 0.25M and the water is just dribbling then it means that the imbalance or differential pressure across the H is 0.25M, so increasing the distance beteen the waterlevel and the top of the vent by either raising the vent pipe or lowering the water level should have the same effect IMO, rem its a U tube we are talking about, anyway there's reall nothing to be gained with this cistern.

[marshian]

13 minutes ago, Peaklander said:

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.

 

Why didn't you try PP1 ?

[Peaklander]

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.

 

[ProDave]

Most old school plumbers took the vent pipe as high as possible before turning back down.  A new bit of pipe and a coupling or 2 would be a very easy and cheap way to achieve that, far cheaper and quicker swapping random pumps etc in the hope of finding the "fault"

[Peaklander]

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. 😊

[John Carroll]

There's bags of headrom there to do that, its amazing that none of the plumbers spotted that, that's just basic stuff, you could do that yourself in less than hour.

Did any of the plumbers look up there in the attic?.

Edited January 4 by John Carroll

[marshian]

13 minutes ago, Peaklander said:

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.

 

You can always open the lockshield end of the rads to allow a little more flow on a lower pump speed - but I can understand why you wouldn't want to leave them with a cooling house

 

13 minutes ago, Peaklander said:

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.

 

Your tank level already looks a heck of a lot lower than mine - you don't want to end up with the opportunity for the top up (cold) to allow air to be sucked in to the circuit

 

13 minutes ago, Peaklander said:

 

Oh I'd definitely be raising the vent pipe even if I had to run it up following the angle of the roof truss and then bring it back down

 

I relocated and lifted my cold water tank and my F&E tank a couple of years back - it was in a bloody stupid place right by the loft hatch and I used to catch my back on a support beam every time but I kept the height of both HW Tank Vent and CH circuit vent the same above the tanks

 

New frame at the back of the loft

 

Old one at the front by the hatch being dismantled and removed

 

 

I hate waste so I may have built a ladder for my mates pit out of the removed timber

 

[Peaklander]

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.

[marshian]

PS off topic but just to say I fabricated (welded up) some hanging brackets for the pit ladder so that in the winter when the pit can get a bit wet (high water table) the ladder can be swung up and tied off - That was just a check it fits in the hole shot

[marshian]

Just now, Peaklander said:

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.

 

Oh absolutely that is the case - drip feeding information takes ages to get to a root cause or resolution

[Peaklander]

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.

[Mattg4321]

Start with the simplest/cheapest fixes and go from there. 
 

Raise vent pipework

 

Check H pipework

 

Consider blockages elsewhere - heat exchanger potentially 

 

 

If raising the vent pipework cures the issue, happy days. I still suspect there is a partial blockage somewhere, but it might be years before it causes a further problem, if ever. 

[Peaklander]

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

[marshian]

28 minutes ago, Peaklander said:

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

 

Well it's pretty clear that that's the smoking gun found I've not seen a valve that choked before but I have seen a pump that was pretty similar

 

Have you had a magnaclean or similar installed in the system yet - If you've put Fernox F3 in the system it's probably going to free up other deposits I'd want something in the circuit to collect them rather than letting them build up

 

And yes you can look at it as £5 K saved (for now)

 

Now do you still have the old Grundfos pump

[Mattg4321]

Well done. 
 

As above, get a magnetic filter on there assuming there isn’t already!

[Peaklander]

On 03/01/2025 at 22:12, Peaklander said:

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.

 

 

Yes got one.

[John Carroll]

If the vent height was like it is now I'd say you would never have had a problem because of that big bore 28mm? H.

[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. 

[Peaklander]

On 07/01/2025 at 20:09, marshian said:

Now do you still have the old Grundfos pump

It’s yours. Let me know what you want to do.

[marshian]

12 hours ago, Peaklander said:

It’s yours. Let me know what you want to do.

Excellent Thank you very much - I’ll send you a PM

[marshian]

Well @peaklander sent me his old pump and tonight I had chance to strip it down and transfer the speed controller (to replace the one on my pump which was broken by a hamfisted gas engineer)

 

Easy job but being of an inquisitive mind I couldn’t resist stripping it down completely and I wasn’t surprised at what I found

 

this post is with permission of Tim @Peaklander 

 

this is the impeller from above

 

side view

 

 

other side

 

 

I could only find a couple of channels that looked like they would pump water

 

 

[marshian]

Gave up trying to clean it out after removing this much detritus

 

 

pump has a much thinner impeller than my one despite being the same pump???

[John Carroll]

All because the vent wasn't carried up and over the F&E Cistern originally?.

[marshian]

28 minutes ago, John Carroll said:

All because the vent wasn't carried up and over the F&E Cistern originally?.

 

I don't think so @John Carroll I think @Peaklander parents system is dirty - the magnetite has built up in the H above the pump and in the pump itself

 

The original issue was probably caused by the blockages in the pump impeller but replacing the pump for a new one (and probably much more powerful in terms of flow rate) resulted in the pump over that wouldn't have happened with the original pump

 

It's not the first time I've seen a pump restricted like this it happened to my own system - I couldn't work out why a system that had run for 15 years on the lowest pump speed and the boiler was happy and then I needed to use speed two to reduce the boiler short cycling because it was unhappy

 

It took me a long time to work out what was happening - probably too long if I'm honest

 

I'm adding to the post just so anyone searching for similar faults can see that a check on the pump might be a good first port of call

[John Carroll]

Well, I think what I have learned from this thread is that the first port of call should be to ensure that the vent is installed properly, ie, up and over the cistern, even with a perfectly clean H there was bound to be some carry over and aeration with that installation, there are literally dozens of houses around me, some, with the combined cold feed and vent and some with the H, some have never ever had a drop of inhibitor since these houses were built, over 50 years ago,  yet some have rads, like my own, 30 and 40 years old. I can only assume that no air is ever entering the system(s) and obviously no system leaks.