Overflow pipe from tank in attic

OK closed that , only took about half a turn and its not so much a wheel type
but more of a knob type what should i expect
 
Not a lot I would think.

Unlikey to be hole in cylinder.
Are the tanks still overflowing?
Have you checked the ballcock in tanks again, this is the most probable cause.
 
ok ,went up and had a look at tanks , pipe from right hand base of cylinder that goes up into attic and is connected to both tanks at base of each is warm all the way up and you can actually see the waves of tha warm water entering tanks.Ballcock not letting in water and tank is about to overflow. What the hell is causing that ?? frustrated now!!
 
ok.
You have hot water expanding back through the cold fed to cylinder?

At the moment you have heating on?

Off the top of the cylinder there is a hot draw off pipe and an expansion pipe that hooks over top of tanks, ensure this is not obstructed or blocked.

As mentioned earlier it may be a faulty immersion. you should use a phase tester to prove that no power is going to immersion when switch is off. The fault would be at the switch, theromstat fault at immersion.
 
Heating off since 8pm , cant see any obstruction to expansion pipe , pipe from top of cylinder to expansion pipe is cold , will check immersion to seeif its on constantly but
that would mean we have constant hot water but we dont.........if its not the immersion have we exhausted the possible causes?
 
How is it today?

You have isolated water entering the heating system? By way of shutting off auto filling valve.

Does it still overflow once heating is off?
 
Hi Davyjones , Shut off valve as you said , still overflowing and no heat or
immersion on today , had a look about an hour ago and problem
is definately water coming back up the feed pipe from cylinder to storage tank when it should be going the other way as needed.

That would suggest pressure causing it to rise am i correct?
So does that mean hole in coil ?
 
We need to isolate filling valve from system to ensure it is off?

To do this shut down mains..check tank, water should now have stopped back feeding?

either blank or valve mains side of auto filling valve and turn back on water. If it stops, then you have hole in coil.
 
Davy , update for ya , tanks overflowing this evening as usual got young fella to turn
off feed from tank to cylinder and straight away water started coming out expansion pipe.
Does this confirm hole in cylinder causing water to feed back into tank?
Also should i leave the filling valve for heating shut off?
 
Looks like the only thing it can be. The auto filling valve is letting.

Does the water stop when you turn off mains?

I don't understand your last question.
 
Yes overflow stops when mains is turned off , should the knob on the auto filling valve be left closed tightly all the time.
 
Your best bet is too replace the auto valve for a filling loop. you could also fit a gauge nearby to allow you to observe pressure drop.
 
Problem solved , while in the process of replacing cylinder plumber noticed water flowing back into cylinder from pipe that feeds hot taps while cylinder completely
disconnected.
Turns out mains pressure was crossing over mixer taps forcing water back up into
cylinder and up to tank through cold water feed and causing tank to overflow.

Fitted non return valves to taps to stop this , seems to have worked o.k.
 
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