Worcester Greenstar 25i ERP siphon won't drain, condensate pipe clear

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Hi all
Firstly I will say I am aware the boiler cannot be touched other than by a Gas Safe engineer, I am only looking for information I could give the service company a nudge with as after several visits by said engineers, problem remains.
It's a Worcester Greenstar 25i ERP condensing boiler 2yrs old.
Initial issue was bubbling/ gurgling from boiler and flue and no hot water.
The trap/siphon fills completely all the way to the heat exchanger and doesn't drain.
Multiple engineer visits follow same pattern of them suspecting condensate drain pipe is blocked, they find it isn't, drain the siphon then go on their way.
They are always adamant it is solved.
But siphon refills over time and they have to come back and so the cycle continues.

Is there anything else that could be causing this? The trap has been cleaned, it fills to the point that it flows into the holding chamber, when that is full it never actually siphons away, it then just fills up the whole trap and in to the heat exchanger /flue.
When they get it out and fill it from the tap it siphons ok. It appears to be a simple thing, but the solution seems to allude them, anyone know what may cause this siphon problem when on the boiler or experienced similar? When they fiddled
about with it on one visit it siphoned itself and drained away as it should, but won't do it itself in normal use.

Thanks
 
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Some syphons are prone to this, the problem is almost always with the condi pipework.

Can be partial blockage at end of pipe, insuffient drop on pipe before a horizontal run, or something causing a tiny positive pressure in the pipe.

Needs investigating carefully
 
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Unfortunately I don't have access it is either behind kitchen cupboards or in a main drain boxed in, in bathroom.
 
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Unfortunately I don't have access it is either behind kitchen cupboards or in a main drain boxed in, in bathroom.
sounds like an install problem, this pipe needs a fair level of fall back, the syphon on these is designed to drop larger amounts of water rather than trickle like some do, but they have to be fitted properly
 
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I could understand that if it hadn't been working ok for 2 years and its predecessor working ok for nearly a decade. Could an install problem suddenly crop up like this?
 
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I could understand that if it hadn't been working ok for 2 years and its predecessor working ok for nearly a decade. Could an install problem suddenly crop up like this?
would be unusual, but if the connection to the drain is close to a sink or washing machine connection, it is possibly partially blocked at the connection and building up, a common problem
 
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hi
did you resolve this problem, i have exactly the same symptoms ?.
regards mike
 
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I've got the same problem. I have the condensate going into a condensate pump. The fall seems OK. Made sure the condensate pipe is clear. But this fault keeps coming back. If I simply tap the condensate trap in the boiler it drains.

I'm wondering if the condensate pipe is in the water in the condensate pump causing some sort of pressure.

The trap seems very fiddly and I have replaced it once

I am gas safe registered

Be Interested to know what's happened in previous jobs here
 

CBW

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Hi Derek,

A couple of things: you’ve hijacked an old post, which is against forum rules, that also has a different setup than yours (gravity vs pump). Also you could join the CC and ask in there ;)

P.s. photos help massively.
 
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It's my first time here so sorry wasn't aware of the rules

What do you mean by i have hijacked an old thread. I have the same exact problem. I simply Googled this issue and this thread came up.

I was simply trying finding out what has happened with the other issues whilst sharing something that I have come across
 
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