F&E Tank Overflowing HOT water

[Steelasophical]

F&E tank filling up with HOT Water + overflowing. All rads are hot Home Service engineer recently changed normal valaves on radiator to TRV's. ByPass is open. Tank has around 1m of head, as boiler is situated in the 1st floor bedroom cupboard. Cold Water Cistern & F&E tank are on the base level.

What would be the cause of hot water pumping over into the F&E tank?

 

[masona]

Possibly the boiler is overheating the water too quickly as you now got TRV's,try turning down the boiler thermostat down.Probably what happen is the water is turning to boiling point which is pressurizing and goes straight out to the F&E tank as it got nowhere to go.

 

[Steelasophical]

Could this also be due to a faulty Hot water Cylinder?

 

[masona]

Try this simple test first,turn down the boiler thermostat down and see what happen.What I need to know is,did this happen after the TRV's installed or was it doing it before.

 

[Steelasophical]

Problem occured before the TRV's were fitted, but filled up much quicker after they were fitted.

I have turned the stat down and the F&E tank is still filling with water from the expansion pipe.

 

[masona]

I don't think its your hot water cylinder yet as you would normally get dirty water out of your hot taps.Have you renew your pump recently,if so turn your pump setting to low speed as it could be pumping over.

 

[Steelasophical]

Although the system seems to work better on speed 2, I have tried it on 1 for long period of time.

The system still filled with hot water!

 

[masona]

hmmm ! Okay need more info..

1,How old is the system ?
2,Is the ballcock shutting down in the F & E tank okay ?
3,Is the water filling up via the vent or the feed ?
4,Is the water coming out of the overflow clean or dirty ?
5,Does it still fill up when hot water & radiator not on ?
6,Have you had any work done on the system recently ?
7,Is it cold or hot water coming out of overflow ?

 

[Steelasophical]

1,How old is the system ?
No Idea....Rads are very old. Boiler is a Glow Worm Fuel Saver Mk11
2,Is the ballcock shutting down in the F & E tank okay ?

3,Is the water filling up via the vent or the feed ?
Expansion Vent pipe

4,Is the water coming out of the overflow clean or dirty ?
Looks Clean as it comes out of the overflow and hits my Sat Dish!!

5,Does it still fill up when hot water & radiator not on ?
NO

6,Have you had any work done on the system recently ?
Have had 5 sets of rad valves changed

7,Is it cold or hot water coming out of overflow ?
Warm/Hot. The hot water from the expansion mixes with the cold water in the tank

 

[masona]

Check the pump is going right direction (you will see a arrow on the pump) also make sure the radiator flow valves are fully open and not cut down when you had the TRV's installed.Somewhere you have a restricted flow possible sludge/block. If that okay then possibly a bad design,the only thing I can think of is which shouldn't make any difference as you not has this problems before that the F & E tank is on the same level as your cold storage tank and the F&E tank not being high enough above the water level in the cold water storage tank causing to pump over.You might have to raise the F&E tank up higher but you really need someone to look at it for you before you do.

 

[Steelasophical]

The system does appear to have a high level of sludge resident. Enemthe base of the F&E tank is full of sludge. What would be the best 'cost effective' means of cleaning out the system.

AS you have indicated, it could be a possibility that the sludge in the system could be causing a blockage.

Someone had suggested forcing the ball valve closed for a period of time, as a means of proof of a problem with the HW cylinder.

Looking at the system, I have found that one downstairs rad has been piped wrong, or rather the TRV has been placed on the return. Problem is, it is not a bi-directional valve.

 

[masona]

You could try and shutdown the cold feed or ballcock to the cylinder then put the heating on and see what happen.Without looking at your system,I think you got a restricted flow somewhere.If it is heavy sludge then have a look at this website for sludge remover www.fernox.com .You could also have your system clean by power flushing which is not cheap.

 

[Steelasophical]

Done a little experiment. For the past 2 weeks, the ball valve has been latched up preventing the F&E tank from being filled via the cold water supply.

The tank level is still rising with water flowing out of the overflow pipe.

Any ideas?

 

[Jim]

Had the same problem and it was caused by the coil inside the hot water cylinder being ruptured allowing crossover of central heating and hot water system. Solution was a new cylinder and problem resolved.
Jim

 

[masona]

This is probably where your restricted flow is,inside the cylinder coil.The only thing to do now is to take out the cylinder,flush the coil with water and see what come out.Inspect & pressure test,then go on from there.Make sure you can get one available if it is faulty.