open vented system sucking in air HELP PLEASE

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benthetroubled

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Hi my mother in law has an open vented system running three radiators no hot water. the pipes froze and split last winter and as it is holiday cottage i didn't notice till the pump hads burnt out i replaced the pipes and the pump (my friend a plumber came and checked it was all alright).
It has a combined overflow and fill pipe just before the pump, but for some reason it now just sucks air in all the time instead of water and sounds like theres a plane taking off upstairs every hour. I asked my mate but he cant think what is wrong so advised me to swap it to a sealed system I was just checking on here if there was another option like auto air vent or separate pipes for the overflow and fill, or if its something else all together. I am getting desperate with it so aNY ADVISE WILL BE MUCH APPRECIATED AND listened TO THANKYOU IN ADVAnce for any help you can give
 
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with a small system like that the pump need only be set on the first speed, as they come set on the number 3 speed turn it down to the first, that will stop it dragging air in,
 
Thanks for that will try it when I get home tonight didnt even crossd my mind to turn the bloody thing down after i fitted it, cheers again.
 
It will be something very simple but without full details and photos we cannot guess at thw fault.

Why dont you want your plumber to fix it or is it just the cost?

Dont expect a professional to be keen to do himself out of a paid job!

Tony
 
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If as you say you have a single 22mm combined feed and vent connected correctly to the expansion tank,ie well below the water level then air should not be drawn into your system.Needs a bit more info for an answer.
 
Hi there my plunmber mate hasnt got time hes sflat out constantly and he is just as tumped which is why he said just turn it into sealed system. Cost is a slight factor but if needs must we will get another plumber in but if anything it has me intriguid as to why after 13 years of working properly it has now started doing it its almost turned into a sad sort of quest and yes it 22ml pipe the fill tank is 1 1/2 mtr above the pump . what other information do you need
 
Combined feed and expansion pipe cannot draw in air.

Might be something else that makes you think air is being drawn in.

You cannot just convert any open vented system to sealed system- you will need to check the boiler manual to see if the system can be converted to seal system. But then be prepaired to accept sealed system problems.
 
It can't be sucking air all the time unless there's water going out ;)

It's probably just trapped air, which hasn't got out yet. Have you vented the hot water primary pipes? Bleed point of some sort is likely to be at the arrow:

I had a pic of that...
lost it, did another..
38194058.gif


It's possible to have micro leaks on the inlet side of the pump which let air in but not water out, so you get a small amount drawn in when the pump starts. CHeck everything is tight
 
Agile said:
It will be something very simple but without full details and photos we cannot guess at thw fault.
Click to expand...
Shame on you Tony.
I can guess the fault.
My guess is that he stuck the pump in upside down.
 
Erm wow loads of help thanks everyone,,

The reason I think it sucking in air is the noise and whenever I have to shut the system off because the knocking is so violent after a few hours of running. I can bleed the highest radiator for about 5 mins then leave for an hour then have to do this twice more after that I cant get any more air out so turn on runs fine for couple hours then starts banging again.
I have bled the pump, when i installed it had it pumping the same way as the old one was.
I don't want to make it a sealed system unless we have to, as the boiler is about 14 years old and not sure it could handle it.
I cant find hot water primary pipe vent it doesn't run through the immersion tank. !!!!
Will try tightening all the joints again.
 
Your first post said noise like airplane taking off. your next one said banging.
Which is it.
If its banging, It could be Kettling
What boiler have you got
 
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