Brown Hot Water - leaking coil?

I've been to a friend of a friends today to investigate "brown bath water"

When I got the call I suspected a leaking coil in the cyl.
Arrived, the bath water definitely had a brown tint to it.
http://i125.photobucket.com/albums/p65/PTFEphoto/DSC00127.jpg

Although I'm aware of the problem of a leaking coil I've never done one, so any advice on what I've done below would be welcome.

System:
Conventional boiler
Vented system
Indirect cylinder
CWSC and F+E cistern both plastic, neither had lids on.
Lots of limescale on the cistern ball valves

I left the bath hot tap running and went into the loft to have a look to see if the F+E cistern was running to replace the water escaping through the coil, but there didn't seem to be any sign of water movement either in or out of the F+E. There was a coating of rust on the sides of it though.

CWSC:
Water appeared clear, with a small amount of what looked like dust settled at the bottom. Certainly not enough to cause the problem.
Limescale on ball valve appeared to be inhibiting the flow of mains water to the extent that the bath tap was draining the CWSC faster than it re-filled.

I also drained about 1L of water from a downstairs rad to see what condition the CH was in and it looked very clear.

So my question(s)
1. If the coil is leaking is it likely that I would see the F+E ball valve open or is the leak likely to be so small that it would take quite a while for the ball to drop far enough?
2. Is it more likely to be sludge at the bottom of the DHW cyl?

I've left them with it for today, but not to bath in it!
I've told them it may still be the coil, but it could be just sludge and that I'll take some advice. And to get some lids for the cisterns.

Any advice please?

Thanks

PTFE

 

Sounds like the coil may have gone,are the storag
e cistern and the heating F&E tank at different levels?
usually the lowest one starts to overflow.

Both at the same level. No sign of any overflowing.


if it was a leaking coil there'd probably be a 'pumping over' situation

I'd have thought that there'd be 'pumping over' into the F+E if the coil had a hole/split, but the water was going INTO it i.e. the CWSC was higher the the F+E cistern and therefore delivering a slightly higher pressure?
But in this case something is contaminating the tap water.


are you sure the brown is coming out of the hot tap?

Yes, positive.


isolate the cws from filling up the copper cylinder
run hot tap till its stops put boiler on water then
if your hot tap starts running again you topping up
cylinder from coil.

I hadn't thought of that, I'll have a go.

looking at that i would say there's a coil problem.

I think so too, thanks for the replies so far.

PTFE