F & E Tank Overflowing

[Bigily87]

just get a combi boiler and throw them tanks away.

 

[denso13]

I can only think that air is the problem.

A part blockage is most likely the problem.

 

[Madrab]

It a well know issue with OV systems and corrosion usually gathers around the 'H' section where the feed and vent couple into the system. When an OV systems cistern either overflows or it's pumping over then it's an well known fault finder to check using a magnet to test for magnetite coating the inside the pipe. If there's enough magnetite to hold a magnet onto the copper then an experienced installer knows it's a sure sign it's blocking up in there, will invariably be the cause of the problem then cuts it out and replaces.

 

[Johntheo5]

I wouldn't disagree with that, but what I do find difficult to grasp is the "constant" overflowing, if the ballcock was tied up then surely there is a limit to the overflowing?, I also can't grasp the fact that the system alone can provide even enough to fill the F&E even once except that air is being drawn in and on heating is displacing the water, the cause of air being drawn in through the vent can obviously be a partial blockage or far more unlikely, circ pump installed wrong way round.

 

[Madrab]

oh and just for a balanced view

 

[bennyd]

This is a very interesting problem, wonder if the pump is drawing air in through the vent which when heated will displace the water to cause overflow, I know you said system worked OK since pump renewal in Dec but can you check sometime that the pump is pumping downwards to the midposition valve, you might also hold a plastic glass of water under the vent with pump/HW on and see if it's drawing air in. If the level overflows each Time the HW is on and if the ballcock never makes up then I can only think that air is the problem.

No air is being drawn in from the vent. The pump is in the correct orientation.

I wouldn't disagree with that, but what I do find difficult to grasp is the "constant" overflowing, if the ballcock was tied up then surely there is a limit to the overflowing?, I also can't grasp the fact that the system alone can provide even enough to fill the F&E even once except that air is being drawn in and on heating is displacing the water, the cause of air being drawn in through the vent can obviously be a partial blockage or far more unlikely, circ pump installed wrong way round.

Its not filling through the ballcock valve, its filling through the pipe at the bottom (The blue one on my photos, im not sure what its correct name is). The ballcock valve is closed as its meant to be. I have tested this by emptying the tank cistern to a low level and seeing it fill to its set level (about 1/3 full) before closing.
Its only a "constant" overflow when the hot water system is on. Its a dribble/fast dripping, not a torrent. I assume this is the rate at which it is filling. It stays at this full level until i empty it, but it drops to just below the overflow pipe (as you'd expect) after a little while. The next time the hot water comes on, the cistern is already full so the overflow starts near enough immediately.

 

[Madrab]

It stays at this full level until i empty it

maybe I didn't pick up on this in earlier posts, or it wasn't clear. If the F&E cistern is filling up when warm/warming up and staying that way when it cools then there may be something else going on. If it was just a blocked 'H' section then I would expect the level to drop back down when the system cools and then the cistern would need to make that up.

As was suggested at the start though there could also be a cylinder coil problem. If the cistern fills up and then stays at that level then that behaviour suggests there is water being added from somewhere be it the F&E cistern or the coil. Does the level change when the only the CH is on and not the HW?

I think you need to have a pro in that is experienced with OV systems to fault find, the behaviour of the cistern when the system starts and runs needs watched, does the level drop in the cistern and the valve makes it up?

 

[Johntheo5]

No air is being drawn in from the vent. The pump is in the correct orientation.

Its not filling through the ballcock valve, its filling through the pipe at the bottom (The blue one on my photos, im not sure what its correct name is). The ballcock valve is closed as its meant to be. I have tested this by emptying the tank cistern to a low level and seeing it fill to its set level (about 1/3 full) before closing.
Its only a "constant" overflow when the hot water system is on. Its a dribble/fast dripping, not a torrent. I assume this is the rate at which it is filling. It stays at this full level until i empty it, but it drops to just below the overflow pipe (as you'd expect) after a little while. The next time the hot water comes on, the cistern is already full so the overflow starts near enough immediately.

This is the conundrum, don't know what size your tank cistern is but mine is 36L, 40X30X30cm, then 1cm = 1.2L and using this as a guide, at a third full when cold it will contain 12L at a level of 10cm, you then put the HW on, the primary circulating flow should then only be 15L or less (gas boiler?) if the average temperature of the the primary water is 60C then the expansion volume is less than 0.25L so the tank cistern volume is now 12.25L at a level of 10.2L, if the overflow is say 10cm from the top then the water level must rise by another 9.8cm or 11.76L to reach the overflow, since you have confirmed? that the ballcock isnt making up then where is this relatively enormous volume of water coming from, scarcely from the system?.
You can measure your own tank cistern to see how much exactly is required to overflow.

If the heat up time is say 30 minutes then 0.25L will overflow if the level is allready at the overflow, 0.25L in 30 mins = 8ml/min, just dripping.

 

[bennyd]

maybe I didn't pick up on this in earlier posts, or it wasn't clear. If the F&E cistern is filling up when warm/warming up and staying that way when it cools then there may be something else going on. If it was just a blocked 'H' section then I would expect the level to drop back down when the system cools and then the cistern would need to make that up.

As was suggested at the start though there could also be a cylinder coil problem. If the cistern fills up and then stays at that level then that behaviour suggests there is water being added from somewhere be it the F&E cistern or the coil. Does the level change when the only the CH is on and not the HW?

I think you need to have a pro in that is experienced with OV systems to fault find, the behaviour of the cistern when the system starts and runs needs watched, does the level drop in the cistern and the valve makes it up?

I havent put the CH on recently and i can only have the CH on at the same time as HW. I have not noticed the level drop when the water is cooling and i have not been up in the loft at the time the HW turns on, but i can arrange that to see what happens. Should it drop a bit when the pump starts? I have left the loft hatch open and have no heard that cistern fill up through the ballcock valve. I can hear the cold water fill so i should be able to hear the F&E fill as its closer to the hatch.

This is the conundrum, don't know what size your tank cistern is but mine is 36L, 40X30X30cm, then 1cm = 1.2L and using this as a guide, at a third full when cold it will contain 12L at a level of 10cm, you then put the HW on, the primary circulating flow should then only be 15L or less (gas boiler?) if the average temperature of the the primary water is 60C then the expansion volume is less than 0.25L so the tank cistern volume is now 12.25L at a level of 10.2L, if the overflow is say 10cm from the top then the water level must rise by another 9.8cm or 11.76L to reach the overflow, since you have confirmed? that the ballcock isnt making up then where is this relatively enormous volume of water coming from, scarcely from the system?.
You can measure your own tank cistern to see how much exactly is required to overflow.

If the heat up time is say 30 minutes then 0.25L will overflow if the level is allready at the overflow, 0.25L in 30 mins = 8ml/min, just dripping.

My cistern is about the same size as yours. Some of my earlier guesses may have been slightly off, but i'd say a rise of about 10cm from the ballcock valve stopping and the overflow pipe is about right and the cistern stops filling from the ballcock at around 12cm full.
I emptied it yesterday afternoon (to the 12cm level) and the HW has been on for 45mins yesterday evening, 1.25 hours this morning and is just about to turn off after being on for 45 mins this evening and it only looks to have risen about 1cm (that about as far as i need to push the ball down to make it start filling) and the water and pipe is cold (as cold as it can be up there today). Im not sure what is different other than playing with a magnet.

You are both correct in wondering the mystery of where the extra water is coming from and i'll see what i can do to monitor this, but at the moment i have no answer.

 

[Johntheo5]

Can you just get the level to its normal ~12cm level doesn't matter whether cylinder is hot or cold and tie up the ball cock and keep a eye on the level for a few days.
I have a isolation gate valve on my ballcock makeup and it's closed permanently, I open it a few times a year and have never ever heard it making up a single drop of water.

There's no solid fuel system disconnected or not, around?.

 

[bennyd]

Can you just get the level to its normal ~12cm level doesn't matter whether cylinder is hot or cold and tie up the ball cock and keep a eye on the level for a few days.
I have a isolation gate valve on my ballcock makeup and it's closed permanently, I open it a few times a year and have never ever heard it making up a single drop of water.

There's no solid fuel system disconnected or not, around?.

No solid fuel system. I will tie it up and see what happens

 

[bennyd]

I do have an isolation tap, but its jammed so I tied up the ballcock last night, shortly after my last message. The pump is on speed 1, the water level is now about 5cm from the overflow pipe and the HW was on for 1.25 hours this morning and has currently been on for 25mins this eve so far (will go off in 20mins) so thats around 6 litres of water that have entered the cistern.
The water in the cistern is room temperature, but the pipe leading to it from the HW system (the blue one on my photo) is hot up until about 70cm above the T piece and rising.

 

[Johntheo5]

You could mark the level once the heating cycle is finished for the night and see if it has risen overnight before heating comes on in the morning.
The only way to rule out the CWST is to drop the level and keep it slightly below the F&E cistern level for a few days with the (F&E) ballcock still tied up but this may prove to be messy, you could maybe do it over the day heating period.

 

[denso13]

I do have an isolation tap, but its jammed so I tied up the ballcock last night, shortly after my last message. The pump is on speed 1, the water level is now about 5cm from the overflow pipe and the HW was on for 1.25 hours this morning and has currently been on for 25mins this eve so far (will go off in 20mins) so thats around 6 litres of water that have entered the cistern.
The water in the cistern is room temperature, but the pipe leading to it from the HW system (the blue one on my photo) is hot up until about 70cm above the T piece and rising.

You have magnetite in the pipework, get that fixed (cut out) and go from there. You could ask them to check the coil, if they can, while they are there. Theory can only go so far.

 

[bennyd]

You could mark the level once the heating cycle is finished for the night and see if it has risen overnight before heating comes on in the morning.
The only way to rule out the CWST is to drop the level and keep it slightly below the F&E cistern level for a few days with the (F&E) ballcock still tied up but this may prove to be messy, you could maybe do it over the day heating period.

The CWST is higher than the F&E cistern so thats not possible? The ballcock level in the F&E is roughly (by eye) the level of the bottom of the CWST. Unless i've misunderstood what you've said?

You have magnetite in the pipework, get that fixed (cut out) and go from there. You could ask them to check the coil, if they can, while they are there. Theory can only go so far.

Having magnetite in the system is the only thing we've been able to confirm 100% so its still the leading theory and will be what i tell the engineer and hope there is no other issues. The source of the excess water does seem to be a concern though. What are your thoughts on where this is coming from? Or is the only possible source now the coil?