Dirty water in F&E tank

[eltommys]

Could someone please advise possible cause of dirty, black water in F&E tank. This tank is also overflowing with a small drip coming out of the overflow pipe. I recently replaced the hot water cylinder (thought the coil inside the cylinder was leaking) and installed new upstairs radiators also. Flushed the completed system through also. (Downstairs radiators are old) The CH system is oil fired, gravity fed and is approx 30 yrs old. The boiler was exchanged about 15 yrs ago. The bathroom shower comes off mixer tap fed by mains cold and hot water from cylinder. Just fitted a one-way valve to the hot feed to the mixer tap just in case of back flow. I cant detect any water entering the F&E tank via the vent pipes. Also isolated the cold water feed by tying up the ballcock - I assume it's entering back up through the feed pipe? I guess the coil in the new cylinder could be leaking but being new I have my doubts.

Any suggestions would be appreciated......?

 

[Bahco]

It sounds as if your system need de sludging. Add cleaning chemicals and flush out, then add inhibitor.

Your problem may be down to you not allowing for water expansion, the sludge entering your tank when hot
When your system is cold your f/e tank should have a water level of 10 cm. Set your ball valve to cut off at this water level.

 

[kevplumb]

possibly a blocked vent

 

[eltommys]

Thanks BAHCO and kevplumb.

Kevplumb - if the vent was blocked what problems could result?

 

[kevplumb]

the expansion of the water when heated back's up through the feed pipe

 

[eltommys]

Would this cause any damage?

 

[kevplumb]

will if the feed gets blocked

tends to result in large amounts of water coming through ceilings etc