Hot water expansion tank overflow dripping

[SimplyWendyful]

Hello everyone.

I have noticed that the overflow from the CH H/W expansion tank in the loft has started dripping.

I investigated today and found that there’s a pipe running up through the ceiling into the loft and into the top of the tank and this pipe has hot water running out of it. If I turn off heating the water seems to stop, as does the dripping. It’s not leaking in the loft, but it’s soaking the path outside!

Any idea what could be causing this?

 

[terryplumb]

When system is cold where is the water level up to in the f&e cistern ?
It only needs to be a few inches deep.
The system sounds like it's over pumping ,possibly due to a restriction in the pipework. Show us pictures of all pipework around the pump and hot water cylinder.

 

[foxhole]

When you say turn off heating you are referring to rads not hot water? do you have electric immersion elements in tank? has someone accidenatly turned them on as well as hot water?

 

[dilalio]

Have you had any work done on the system recently? New pump, motorised valves etc?

If not then it's likely either the ball valve letting by or sludge/restriction in the pipework usually where feed and vent connect.

 

[SimplyWendyful]

When system is cold where is the water level up to in the f&e cistern ?
It only needs to be a few inches deep.
The system sounds like it's over pumping ,possibly due to a restriction in the pipework. Show us pictures of all pipework around the pump and hot water cylinder.

I will need to have a look. I’ll check when I get home as hot water will have been off all day at that point.

When you say turn off heating you are referring to rads not hot water? do you have electric immersion elements in tank? has someone accidenatly turned them on as well as hot water?

Sorry I mean hot water! There is an electric immersion element but we never use it.

Have you had any work done on the system recently? New pump, motorised valves etc?

If not then it's likely either the ball valve letting by or sludge/restriction in the pipework usually where feed and vent connect.

No work done. I don’t know if it’s the ball valve as the pipe that is feeding the tank when this happens is not connected to the ball valve.

 

[Madrab]

If it's the pipe that curves over and into the small cistern that gravity feeds the CH system water, not the hot water cylinder, then as suggested that's called pumping over. If nothing has been changed in the CH system and this has just started to run and again it's not from the fill valve, then that is typically down to the section of the CH system where the cold feed from and the expansion pipe to that cistern meets the CH pipework. The can be shaped as a 'H' section in the system pipework and that is becoming restricted by corrosion and will normally need cut out and replaced.

The way to test this is to find where that section for the feed and expansion is located and test it with a magnet, if it sticks, it's getting blocked with magnetite.

 

[foxhole]

What temperature is your hot water set to on the stat attached to tank ?

 

[SimplyWendyful]

If it's the pipe that curves over and into the small cistern that gravity feeds the CH system water, not the hot water cylinder, then as suggested that's called pumping over. If nothing has been changed in the CH system and this has just started to run and again it's not from the fill valve, then that is typically down to the section of the CH system where the cold feed from and the expansion pipe to that cistern meets the CH pipework. The can be shaped as a 'H' section in the system pipework and that is becoming restricted by corrosion and will normally need cut out and replaced.

The way to test this is to find where that section for the feed and expansion is located and test it with a magnet, if it sticks, it's getting blocked with magnetite.

Ok thanks. I’ll see if I can find what you’re referring to.

 

[dilalio]

is not connected to the ball valve.

That's not right for starters! If you mean what I think you mean?

 

[SimplyWendyful]

That's not right for starters! If you mean what I think you mean?

I don’t know if I do mean what you think I mean.

There are two pipes, one comes into the tank from the side, it is fed from the big cold water tank, it has a ball valve on it.

The other pipe, the one I am talking about, seems to come into the attic from the airing cupboard. It goes up and over and comes down into the tank from the top.

This pipe is not connected to the ball valve and seems to discharge water into the tank,

 

[dilalio]

I don’t know if I do mean what you think I mean.

There are two pipes, one comes into the tank from the side, it is fed from the big cold water tank, it has a ball valve on it.

The other pipe, the one I am talking about, seems to come into the attic from the airing cupboard. It goes up and over and comes down into the tank from the top.

This pipe is not connected to the ball valve and seems to discharge water into the tank,

OK... The pipe you are referring to is the vent.
A cold main is connected to the ball valve and this is to keep the expansion tank topped up but only usually operates during a drain down or when there's a leak.
If the vent is discharging then, as above.