F&E TANK - Please help before I.......

[Redhotferrari]

Hi All,

Firstly, please forgive the long post, I have spent some time investigating this so have a lot of info to put down....I will be forever in your debt if you can help!!

I have a 'normal' Vented system, CWS in loft, with the F&E tank next to it on same platform. Vent pipes go over both tanks with a seperate overflow to each tank. Indirect hot water cylinder, Boiler - An old floor standing Thorn EMI.

My problem is this...Imagine that the F&E tank has the 'normal' level of water (about 65mm?) The inlet valve IS shutting off and working as it should. After about a week of having the boiler heat the water through the cylinder coil, either on its own or heating the CH as well, the F&E tank raises to the overflow level and starts pouring water onto my conversatory roof (very annoying!) The overflow level is about 75mm above the 'normal' water level in the tank. The 'overflowing' only occurs for about 3 minutes after the boiler has been firing for about 20-30mins (recovery time for the hot water cylinder).

I have noticed that the boiler casing and surrounding area get VERY hot when in use.

I have cleaned the system out with chemical cleaner and also flushed all radiators. Changed cylinder stat thinking this might be at fault. Checked that the pump has not seized.Both of these have not worked. Am certain that its not the system design, have lived in house for 3 years, this has only been happening for the last few months.

Have spent the last few hours in the loft, after drawing of a load of hot water and switching the controller on to heat the water the water.

I have not witnessed any water entering the tank from the vent pipe, during the heat up process of the hot water there is very slight movement on the water. At the end of the heating process (about 20mins) the OUTLET pipe for the F&E surges water back into the tank at a quite a rate raises the level of water by about 15mm, this stops and after a few seconds the water level goes back down the outlet to the 'normal' level.

So I have not actually seen the water level raise and stay at that height, I know, not much help really!!!!

Does anyone have any suggestion before I turn into a complete raving mad man about this problem?

Look forward to hearing from you.

 

[Agile]

If the water level in the cold cistern is higher than the F&E tank then the implication is that the heating coil in the cylinder is leaking hot water into the heating system.

If you like inconvenience then you could empty the cistern overnight and confirm that the F&E cylinder level has NOT gone up!

If so its new cylinder time!

Tony

 

[petetheleak]

My theory as well.

such a short answer for a long post.

 

[Redhotferrari]

Thanks for the answers, sorry dont mean to appear stupid.......

Yes, the level of the cold water store is much higher than the F&E, which I assume is correct?

When you say "empty the cistern" I assume you mean empty the cold water store but leave the hot water cylinder full, to then heat up a couple of times in the evening and morning, correct?

Really appreciate your replys.....

 

[Breesey]

Yes. But no need to empty cold cistern just shut gate valve on the cold feed pipe to hot cylinder so that there is no head on the hot cylinder. This is possibly forcing water from the hot cyclinder into the primary water and, therefore, into the F&E and then out the overflow.

You won't have hot water after you do this of course.

 

[TicklyT]

I would suggest running some hot water off after shutting the gate valve on the cold feed. Opening a bathroom tap would be enough. Maybe leave it open (with the cold feed gate valve closed) overnight.

1) Expansion of any water heated in the cylinder may affect results.
2) Gate valves often don't seal completely.

Make sure any immersion heater fitted in the hot cylinder is definitely turned off.

You might even find the water level in the F&E tank then starts to fall.