Had a nice Morso fitted back in November and all been fine. Last few days of rain and I’ve started hearing noises which I had assumed to be stove related – heating/cooling perhaps – ting ting type noise. Turns out it was water dripping, which accumulated on top of the register plate and has now soaked through between the plate and the lintel.

Fortunately I hadn’t got around to decorating that wall! Any ideas of why this would happen? Fairly modern clay chimney flue (no flue liner). Should water be able to drip down to this extent? Or should I be looking at other unrelated causes (roof leak etc)?

Don’t know where you live bit, have you noticed the amount of wind and rain that’s been falling lately?
A flue is a vertical shaft with a hole on top. It’s not water proof. In extreme weather conditions it’s common for flues to suffer some water ingress. Just as roofs also do in wet and driving windy conditions. They also, contrary to common belief, are not water proof.

But the water would drop into the sump and into the stove surely? Otherwise every stove installation in the country would be leading to damaged walls. I was thinking poorly fitted sump perhaps?

Sump?

is this while you have been using it ?

or is it sitting there like an ornament ?

if its in use- somethings wrong.

if its there like an ornament then given the really terrible rains we are getting atm – it doesnt surprise me.

Trail rat – used regularly, just not that night.

I was thinking poorly fitted sump perhaps

sump?

You have an open modern clay type of chimney flue. The flue from the stove more than likely proceeds past the register plate and then vents into your clay flue. Water being driven or blown down the chimney will therefore fall onto the register plate, with the exception of the few unlucky drops that will fall into the metal flue coming out of the stove.

This is why you have water collecting on your register plate. Even with a rain cowl fitted to your chimney pot, the horizontal rain will compromise this.

The concern has to be that you are using the stove regularly, which in itself should evaporate any water that collects on the register plate.

Is the cowl is still on your chimney pot? The recent extreme weather is showing up all kinds of flaws in original build or poor repairs with ingress of water, damp, mould etc etc, so it may be that water has found its way past a poorly fitted piece of your clay liner?

slackalice, the flue from the stove does vent into the clay flue but there was a cone type fixing attached – it was described to me as a sump. In other words, anything dripping / running down the clay flue ‘should’ be gathered by this upside down cone and presumable feed into the stove itself?

Cowl is still there!

If your stove is Defra approved, i’m sure the squirrel is, then i would suggest dropping a 5″ liner down, it’s possible it could be condensation which can be a problem with clay liners.
It is often assumed that water coming down a flue is rain when it is condensation.
In my experience a lot of clay lined chimneys fail the pressure test.
Get the fitter back out to check it.

twinwall – its an S10-40. would condensation be more likely with a wood burner than the old open fire that was there previously?

flue temperature with stove vs open is lower so yes.

My post above still applies, the s10 is pending for Defra approval.
I would not fit a stove to a clay lined chimney without dropping a liner down.

Excellent point twinw4ll.

Thanks twinw4ll. From a lay man’s perspective that there is one of the problems. I had several fitters out and they were split – some suggested liner, most said it wasn’t required. I wouldn’t have got a 6″ liner down anyway, which is what the S10-40 needs. I’ll see what the fitter says

it’s possible it could be condensation which can be a problem with clay liners.

This. Our latest stove install is into an existing fireplace with a clay liner (circa 1985).
My installer flatly refused to use the existing liner with an adapter as he had seen plenty of these installations which had resulted in creosote stained condensation coming down the liner and making a big mess. I had a flexible liner installed and no issues.

I wouldn’t have got a 6″ liner down anyway

That’s what my first fitter thought, but it actually went in fairly easily. You’ll probably find the same.