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Discuss Pump noise and sometimes pulsing in the Plumbing Forum | Plumbing Advice area at PlumbersForums.net

If it draws air in your feed and vent are in the wrong position
 
Does it look wrong in my pictures? Where should they be?

My gut feeling as a non plumber is that this is the underlying cause of my problems

The 3rd one eg right is what you want
 

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If it draws air in your feed and vent are in the wrong position
I agree that this is the first thing to look at but there are other possibilities. I'm struggling with a similar problem and my feed and vent are in the textbook location. It's well known that restrictions in the connections can cause pressure differentials that push/pull water in the vent but in my case there's no significant displacement taking place in the vent.

What if during the overrun period boiling is taking place on heat-exchanger hot spots? I ask because I've noticed the temperature on my boiler display ramping up significantly after the burner is extinguished. I did once see a number in the 90's for a few seconds and that gave me quite a fright. This kind of event will disassociate gas within the water and make it foamy (which the pump will definitely not like). Again, it is far more likely to occur after the system has been running than from cold. I think this is the kind of reason that some systems only seem to behave at lower temperatures.
 
It looks as though my cold feed and vent pipes are exactly as they should be.

I think the last owner of this house gave up on trying to fix it and that’s why they spent good money on a nice gas fire (despite being tighter than a ducks behind by all accounts). Think I might be about to do the same
 
Seal the system then you can seal it at 0.5 bar if you got any hidden pipework in concrete
 
Seal the system then you can seal it at 0.5 bar if you got any hidden pipework in concrete
That’s a good shout. Is there anything that could be a deal breaker here? Will speak to my plumber about this I think.

I think the boiler should be ok as we had the same one in our last house with a sealed system - greenstar ri.

We don’t have any pipes in the concrete/screed ground floor.

Is it a large job/cost? Not too keen on spending fortunes on a system that will quite soon be ripped out!

Most importantly will it actually work and stop air being drawn in so I can run the pump at a sensible speed!?
 
Tbh should be less than £300 depends how much your plumber charges
 
Tbh should be less than £300 depends how much your plumber charges
He owes me a few favours but in that ballpark it seems a no brainer. I’ll save that much over the next 2/3 winters by not having to put the immersion on to make up for the crappy heating system.

Seems like a great option then, assuming it’s very likely to fix this kind of problem?
 
It will stop it pumping over and you can set the pump speed to your system requirements
 
The pump is pumping downwards??, what is the " H" above it and where are the vent & cold feed?. or is the H a combined vent and cold feed.

And is it pumping into the return of the cylinder?.

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Pumping downwards yes.

The H is a combined vent and cold feed.

It pumps into the bottom of the coil in the cylinder - just out of shot.
 
The dead-end pipe (probably part of a bypass) won't be helping as it will be full of air and act like a trampoline when the circulator starts and stops. Water can then bounce up and down the vent. The same thing happens if there's air trapped in pipework or radiators but at least you stand a chance of bleeding them!
 
Not good but It looks like there is a manual vent plug on the top. That combined vent & cold feed will only work IMO if its "static", ie that the vent is just that without teeing off to supply other rads etc and ditto with the cold feed with no returns above the H. I have a 50 year old combined vent and cold feed where the vent passes up (and over) adjacent to the F&E tank with the cold feed teed straight in to it with a very short (<100mm) piece of pipe from the end of the tank, works perfectly well.
 

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Just thought I'd update this as we finally got it sorted!

First the plumber sealed the system and this improved the situation a little as air was no longer being sucked in. However we still had problems with pump noise and pulsing unless the pump was set very low.

Pump inspected again, all ok. The only plausible explanation was then a blockage somewhere/air lock. Narrowed it down to somewhere on the primaries. Took apart again and through process of elimination decided on a blockage in the heat exchanger.

Took a punt on a refurbed one at £75 and got my plumber to fit. Refurbed one looked almost new and came with new seals. Most importantly it's solved the problem finally. Weird symptoms for a blockage in the heat exchanger maybe but there we go. Cut the old one open and it was partially blocked around the flow connection into it.

Thanks all for previous help.
 

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