Water going back into the header tank & possible leak

Hi all,

This morning I was woken by some strange noises coming from the pulsacoil cupboard.
It normally makes a little bit of boiling type sounds during the night but this was more than that.
After a little investigation, it appears hot water is bubbling back up into the header tank, I'm not certain through which pipe (top or bottom) but as they seem to be interconnected I'm not sure that is so important to helping work out what is going on.
It sounds a bit like a gurgling bubbling possibly containing air, and you can here water going into the header tank (So maybe it is the top pipe). The water in the header tank is hot.

After taking off the front cover of the PulsaCoil I could see instantly that the floor area was wet and probably has been for some time.

Looking at the Heat Exchanger, the pipe at the bottom, towards the rear has a drop of water on the nut connecting it. If I dry this off, it reappears fairly quickly but it's not flowing out. Would this be enough to make the floor quite damp? Seems to be quite a bit of water around.

Could this leak explain the water going back up into the header tank?

Looks like it might be the washer. My plan is to replace this first, is it a standard washer I can get from the plumbing merchants?

Oh, checked the hot water from the taps - seems fine. 2 red flashes from the LED on the board.

Many thanks in advance for any advice.

Peter

Ok, I've worked out a little bit more since getting home this evening.

The drip from the heat exchange is only slight, barely filling half a small cup.

It seems the main leak is coming from the Off Peak (Lower) immersion heater.

Looks like I'll be draining it down now, it it likely to require a new immersion heater. (This might explain why it's been noisy?)


Many thanks

Pete

A further update!

As I sat watching the 2000 it appeared to leaking from everywhere.

The lower heating element.

The bottom of the heat exchange (System side rather than fresh water side)

The top of the pipe leaving the top of the heat exchange where it goes into the unit. (again system side)

The top heating element.


I've drained it down. Looks like this is the end of it's days? Does anyone agree/disagree?

Looking at a PCS 150 as a replacement, is this an easy swap in. Same size, inlet/outlet connections?

Anyone seen one for less that £739 inc VAT?


Many thanks again


Peter

Should be a straight swop.
Check the plinth it is sitting on.
They must be fully supported.
1 gallon of water = 10lb
Mike