F&E tank overfilling, not the ball valve

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Hi, just want peoples thoughts on this, I have a vented system, quite old, I have to put the hot water and heating on to get the radiators hot but I can just have the hot water on with no radiators getting hot.

So the problem I have is my F&E tank overfills, it’s not ball valve letting by. It only happens when I put the central heating on, the level in the tank rises rather quickly then very very slowly, and it does seem to be intermittent? Once we have hot water in the cylinder it stays warm for 2ish days (that’s without putting the hot water on again) if there was a pin hole leak in the hot water cylinder coil surely the cold mixing with it, it would all be cold after not long?

We also have solar hot water tubes and a pressure gauge on the hot water cylinder (reads about 3 bar) this does fluctuate (gets higher in the summer and lower in winter) assume it’s to do with the hot water tube temp? I don’t no if that pressure is too high and that’s causing issues?
 
Could it be pumping over or does it fill from the feed? Definitely the f&e cistern?
 
Okay I shall do when I’m home, I’m not too clued up with plumbing can you explain what this will do/why?
You need to find the section where the cold feed feeds into the system pipework and typically the vent will rise up to the F&E cistern. Invariably this looks a bit like like an H section of pipe. If the flow is left to right the the top left of the 'H' will be the 22mm vent, the top right the 15mm feed and the bottom left and right are the 22mm system pipes. It would be reversed if the flow is right to left - try the magnet around this area.

 
Okay thanks for everyone’s comment appreciate it!, I’ve found an area where magnet sticks the pipe starts in as the outlet of the F&E tank then meets a t junction which goes into the cylinder and then maybe down to the boiler? It seems the pipe size shrinks there, I’ve attached a pic , where I’ve got old solar tubes there’s pipes everywhere and hard to trace!
 

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Okay thanks for everyone’s comment appreciate it!, I’ve found an area where magnet sticks the pipe starts in as the outlet of the F&E tank then meets a t junction which goes into the cylinder and then maybe down to the boiler? It seems the pipe size shrinks there, I’ve attached a pic , where I’ve got old solar tubes there’s pipes everywhere and hard to trace!

That pushfit elbow tells me there's been an issue before!

Blocked feed from f&e.

Magnetite. Get it cleared out. Either you or a decent plumber.

Could try a gallo gun if you're up to it, but I'd be poking something up and down the pipe if it's accessible.
 
That pushfit elbow tells me there's been an issue before!

Blocked feed from f&e.

Magnetite. Get it cleared out. Either you or a decent plumber.

Could try a gallo gun if you're up to it, but I'd be poking something up and down the pipe if it's accessible.
Okay thank you! Unfortunately it’s not a straight pipe from the F&E tank, it snakes around a bit!
So unfortunately gunna have to get into the pipework I think
I assume if I drained down the system and chucked some sludge remover in the F&E tank then filled it all up again it wouldn’t really budge it?
 
I assume if I drained down the system and chucked some sludge remover in the F&E tank then filled it all up again it wouldn’t really budge it?

Highly unlikely, Magnetite sets solid and depending on how choked the pipework is, will depend on how much circulation will get through anyway. Best bet is to work out which section is blocked, cut that out carefully so it can be cleaned out, and then you should be able to refit it with suitable fittings to rejoin the pipework as required.

Cleaning will probably involve breaking the crud up with a suitable tool, e.g. screwdriver and washing the Pipework through under a tap.
 

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