Help with back boiler issue

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Hi all

Drained system today as I needed to move hot & cold pipework for new kitchen.

All went well until refil, whereby it now seems I have either an airlock or a problem.

With 3-port valve set to MAN I have expect the system to refill (F&E tank is full), bleed valve on rads open and can hear hissing for a short while before stopping, but no water either coming out. Drain plug beneath pump opened and no water coming out.

Having a look at f&e tank piping, it seems it has been changed at some point and the outlet seems to go uphill slightly, and not sure it this is causing the system not to fill. I have added pics which hopefully help. The outlet seem to be changed to go into the expansion return pipe, as there is another 15mm pipe that has been cut and left in situ.

Any ideas, Im starting to get annoyed with this. Only had the house a week

Thanks in advance

 
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Check that the water level in the expansion tank is higher than the central connection on the 22mm x 15mm tee below the vent bend (if it isn't already)

From the pic it looks like there's an uphill incline rather than a level or downhill flow - i would guess a couple of inches 'above the step' in the tank wall will work o.k.

Normally the water level should be about 4 inches deep.
 
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As Gas2air, trace 15mm pipe from central heating tank in loft.depending on where it connects can be tapped gently at union/elbow/tee whatever to dislodge blockage. Otherwise you have to drain tank, chop out connection and move it.
 
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The outlet from the bottom of the f&e tank is definately going uphill before it connects to the 22mm pipe via a tee

Wondering why someone has butchered it as there is a 15mm alongside the 22mm vent pipe that has been removed from somewhere, still have not and olive on it which can be seen just beneath the chrome elbow.?????!
 
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Check that the water level in the expansion tank is higher than the central connection on the 22mm x 15mm tee below the vent bend (if it isn't already)

From the pic it looks like there's an uphill incline rather than a level or downhill flow - i would guess a couple of inches 'above the step' in the tank wall will work o.k.

Normally the water level should be about 4 inches deep.
m

It's probably, but weird why is was done like this. There is a separate 15mm pipe which looks like it was the old feed pipe.

The f&e tank had more then 4" of water and about an inch below the overflow
 
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Obviously the cold feed (outlet from tank that feeds the heating system) has been blocked in the past, cut out and combined with the vent pipe. There's nothing wrong with doing this but obviously running uphill isn't the greatest piece of workmanship I've seen. However as long as the connection to the vent is below the water level then it will fill. I would be concerned that by draining the system any crap that was sitting in the tank has been drawn into the pipe and is sitting in the corner of the pipe where it begins it's uphill climb. If you try draining the system again does the tank empty. If not then it is blocked. Fortunately it has been done with compression fittings so after baling the water out you can undo the pipe and clear any block out of place.
 
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Thanks for all the replies, hoping to get to try it out later or tomorrow

I do remember the f&e tank being full of crap at the bottom, and the
Pump having black sludge type stuff when the bleed screw opened.

A similar problem happened before I purchased the house, whereby the boiler would keep cutting out. They had the pump changed as it burnt out spinning dry, and said it was due to an airlock. Got a feeling this is linked
 
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Ideally cold feed needs to be before the pump, vent before cold feed 150mm seperation.
 
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Ideally cold feed needs to be before the pump, vent before cold feed 150mm seperation.

I'll close of mains and clear the f&e tank, then check the tee to see if it's blocked. Thinking of making the connection again but slightly further down, there it's not going uphill
 
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What back boiler you got? Thinking overheat stat issues probs not got an o/h stat
 
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