Potential leak - anything I can do to diagnose?

Homer_home

I would dry the carpet , stick some pepper down and see if the wet spot comes back 

I'm guessing it's one of your cars though 

Jeepers_Creepers

Yeah, it's the cat. :-)

Is your system sealed and pressurised? If so, I think you'd notice a drop in pressure on the gauge. It is a weird place for a leak, tho' - as said above, if the rad had corroded right through, there would be blisters and bubbles of rusty paint under that bottom edge at the very least - have a good feel, or use a mirror to check. 

Working_in_pyjamas

Belenus said:

Water can travel some distance from the source of a leak.

What is on the other side of that wall behind the radiator?

Is there a potential source of water there?

Also, what is above that area? We had water pooling on the floor in a first floor bedroom that was coming from a leak in a sloping roof several feet above. The water was travelling down the cavity in the wall. The wall was unaffected and didn't show damp marks.

Thanks, the other side of the wall behind the radiator is an external wall. The room is in upstairs bedroom in a conventional 2 storey house so above the radiator is a window and then the roof.

Working_in_pyjamas

Paula_Smith said:

What sort of central heating do you have? If it is a pressurised system (combi boiler?) you "could" have a pinhole leak from a pipe under the floor, which "could" be pointing upwards and wetting the carpet through a gap between floorboards.

Thanks, it’s a combi boiler and the reason I asked the Q about a leak is that when I bought the house we pulled up the carpet on the landing and in doing so dislodged a nail that had been through a pipe for who knows how long so I was wondering about a leak in an underfloor pipe.

Working_in_pyjamas

Apodemus said:

With the right sort of food colouring, you could probably do a leak test...on the cats!

Absolute genius! Have fed the cats some food colouring and will wait and see! 

Working_in_pyjamas

Jeepers_Creepers said:

Yeah, it's the cat. :-)

Is your system sealed and pressurised? If so, I think you'd notice a drop in pressure on the gauge. It is a weird place for a leak, tho' - as said above, if the rad had corroded right through, there would be blisters and bubbles of rusty paint under that bottom edge at the very least - have a good feel, or use a mirror to check. 

Thanks, it’s a combi boiler and the heating still works with no loss in pressure.

I’ve had some dry kitchen roll over it all day, heating was on this morning, cats have had a wee in the trays and there’s no more ‘water’ appeared so I’m blaming it on one of the cats - strange that they would have an accident in the room where the trays are but no harm done.

Jeepers_Creepers

Ah, you've had the old nail-through-the-pipe malarkey? You were lucky you found this as the nails often rust away after a few years - and then you have a teeny, but often messy, leak. The good news is that the n-t-t-p scenario only occurs a maximum of one time in each household, and you've already found yours.

Yup - it's def the cat...

Paula_Smith

Working_in_pyjamas said:

Paula_Smith said:

What sort of central heating do you have? If it is a pressurised system (combi boiler?) you "could" have a pinhole leak from a pipe under the floor, which "could" be pointing upwards and wetting the carpet through a gap between floorboards.

Thanks, it’s a combi boiler and the reason I asked the Q about a leak is that when I bought the house we pulled up the carpet on the landing and in doing so dislodged a nail that had been through a pipe for who knows how long so I was wondering about a leak in an underfloor pipe.

We had this but it was shortly after the new boiler was installed, and the plumber warned us before he installed it that the new pressure might force some leaks.
The boiler pressure did drop but took a while to do so - I can't remember how long though - a couple of days maybe?

Belenus

Working_in_pyjamas said:

Apodemus said:

With the right sort of food colouring, you could probably do a leak test...on the cats!

Absolute genius! Have fed the cats some food colouring and will wait and see! 

I presume that you are both joking. 

The cat would metabolise any food colouring and it is unlikely to colour its urine.

Years ago as an experiment I tried to colour a house plant by putting red food colouring in the water. The plant sucked up all the coloured water but the leaves didn't change colour at all.

Jeepers_Creepers

And cats aren't any higher up the evolutionary ladder.