Sometimes water dripping from expansion overflow and sometimes sudden water discharge

[Samsg30]

Hi,

I have: -
- an open vented central heating system with F&E tank in the loft.
- Sealed cylinder hot water (megaflow). Guess it won't matter with the issue explained below
- Boiler is flexicom hx30 heat only.

Most often (but not absolutely everytime), water drips from the expansion tank overflow even when only water in megaflow sealed cylinder is heating up and no central heating is running. Sometimes a sudden burst of water comes out as well. *** I can also see some sort of blackish sludge type hanging out of expansion overflow pipe exit on the outside wall ***

Though everything with hot cylinder seems working ok, I recenlty noticed that radiators on the ground floor (in 3 storey house) are not warming up enough. Infact when radiators on top two floors are very hot to touch, ground floor radiators are only slightly hot and I can feel the temperature difference between top and bottom of the same radiator on ground floor.
Last month, one of the ground floor radiator was replaced with new and another radiator was emptied completey for changing lock sheild valve. Whilst partially draining the system for doing above job, just slightly dirty water came out.. light brown in colour.

Also whilst working of partial draining the system, I noticed sludge in F&E tank in loft when I put my hand in the water. I don't know if it is black or brown sludge but guess it makes a huge difference so I am going to check tomorrow.

Please can anyone suggest if dripping water from Expansion overflow (without demand for central heating and only demand for hot water) is related to raidators on ground floor not heating up (may be due to sludge came down to lowest radiators very soon) ? And what actions could I take to identify actual cause and remediate it.

Thanks.

 

[dilalio]

Well, for starters, I'd be recreating the environment where this occurs and get into the loft with a torch and observe the F&E tank to see what happens.
You could have several issues occurring - dirt/blockage(s); over pumping; faulty ball valve!
We need more info on how HW demand is affecting the CH which is to do with your piping, valves and controls but start at the source.

Get eyes on and report back with further details.

 

[Samsg30]

 

[dilalio]

Is water still coming into the tank via the ball valve or is it coming into the tank from the vent pipe?

Is the water warm or cold?
Bail water out of the tank into a bucket or drain some system water from a drain cock on grnd floor if you have one. Get the water level in the F&E down so that the float drops and the tank starts filling, then wait until it refills and see if valve shuts off - could take 10 mins to fully shut and there should be no flow at all.

Or just replace the ball valve anyway and go from there...

 

[bernardgreen]

The valve in the ball cock has failed. At the very least it needs a new washer but may need to be replaced if the vale seats have been damaged.


The orange ball should be floating on the surface. Because the valve isn't shutting off the tank has over filled up to the overflow forcing the ball to be submerged. Submerged like it is means the mechanical pressure on the valve is much higher than the valve is designed for and hence the valve seats ( where the washer fits ) may be damaged.

 

[DaveHerns]

Is the vent pipe too long ? It looks to be lower than the ball valve and the overflow outlet

 

[Samsg30]

Is the vent pipe too long ? It looks to be lower than the ball valve and the overflow outlet

Vent pipe is above overflow.. its just the angle with which picture taken.

 

[Samsg30]

I noticed a drop dripping from valve every 3 seconds or so even when valve is fully pushed up with hand. I am going to replace it.

Just to check, if I cock up replacement, is there any harm in leaving the cold water inlet to the F&E tank switched off for few days until plumber is called? And is it safe to run CH until then? There's around 15L of water in F&E tank so not sure if it used up

 

[dilalio]

If not for too long. It will be fine to leave shut off.

Also, once ball valve is replaced, check that your system isn't filling the tank to above the overflow by the expansion of hot water in the circuit back up the cold outlet from the tank.

 

[Samsg30]

If not for too long. It will be fine to leave shut off.

Also, once ball valve is replaced, check that your system isn't filling the tank to above the overflow by the expansion of hot water in the circuit back up the cold outlet from the tank.

Thanks for the advise. I'll replace the valve tomorrow.. and set the level

Just to clarify my doubt.... the expansion pipe (inverted U shape) is just T off from the cold outlet. When water expands, should I expect water dripping from U shape expansion pipe or from the opening of cold water outlet which ofcourse won't be apparent if water is coming back in.
And what is the purpose of expansion pipe ( i.e. inverted U shape in my sense.. pls correct me if wrong)

Thanks

 

[dilalio]

//www.diynot.com/diy/threads/vent-pipe-central-heating.49750/

 

[dilalio]

https://www.google.co.uk/search?q=s...AUICigD&biw=320&bih=460#imgrc=tQCtQioSwpbxxM:

 

[Samsg30]

//www.diynot.com/diy/threads/vent-pipe-central-heating.49750/

Thanks for sharing the link. So if I understood correctly, expansion U pipe is for air vent and I should expect some water rise from the bottom of the tank via cold outlet instead. I recently cleaned the F&E tank full of black sludge and some algae built up over time. CH system was drained last month and filled with 2 ltr of expensive Fernox F1 inhibitor. Is there anything suggested to put in F&E tank to stop build up bacteria / algae or the small amount of F1 inhibitor being pushed back from water expansion will take care of it.