Quite unconnected with my big leak, I have a smaller leak I need help with

[KatyMac]

My big leak happened last Wednesday & is unconnected with my smaller leak which appeared as a damp patch about 3 weeks ago

It is close to where a pipe goes through the wall, but both sides of the pipe is dry.

Is it likely that the pipe has split within the wall?

not very likely.

is it a cold pipe in a warm room?

condensation.

is it a pipe passing into a rainy area?

rain.

It used to be an external wall - now it's inside the conservatory

The conservatory floor has underfloor heating

The pipe is the utility sink drain which comes through the wall & joins the main water out of the house pipe about 2m further on

Thanks for answering PigletJohn; you have given me such good advise (esp last week)

it's a plastic pipe?

does it seem to be under any bending force, or will it wiggle freely?

It's rigid plastic - there is a joint either side

My dad is flumoxed - he spent years as a building contractor but has been management for decades

I wonder if the cladding/outside finish has come away from the wall & water is getting in. It was one of those only halfway up the wall thick coating painted cream, then plastered over once it was inside

It is cemented/mortored in

it is possible, but quite difficult, to crack a uPVC pipe, mostly by a heavy object falling on and stressing it. The crack is more likely to be at the edge of the wall than inside it. It would be abnormal to have a joint in a pipe inside the wall.

If it is a cavity wall, it might be that water is entering the cavity from above, perhaps from a defective roof or gutter, very rarely from a plumbing leak, and dripping onto the pipe, or filling up the cavity and leaking out of the hole round the pipe.

Could it be either cold bridge condensation

or that the pipe gets condensation round it with in the wall

& then we put the heating on?

Metal pipes often get condensation, plastic pipes don't.

What runs through it?

Is the wall damp?

The plastic one has waste from a utility sink - so washing craft stuff, hands, cleaning etc

The metal one about 10 inches to the left has premixed warm water for the children's sink

Might the metal pipe be leaking or getting condensation when cold?

Leaks are more common at joints but water may run down or along the pipe

Is there a wet window above?

No window above

The damp patch is about 2 foot from the metal pipe & above it

Tie kitchen roll tightly round all pipes on both sides of the wall.

Sorry that isn't true there is a window above the metal pipe but it's an internal window between the utility & the children's toilet

I'll try that tomorrow - good idea

Is condensation or rain coming from the window? Is it a cavity wall (13 inches thick) or a solid wall (9 inches)?

13 I think; it's a 1950s ex council house - so I expect so

The window is between 2 rooms so it sees no rain and no condensation

Is there a flat roof above this wall? Might. there be an old water pipe chased into it and plastered over?

Nope - it's the rear elevation of the house - normal roof

My dad is tearing his hair out tbh he cannot 'find' a reason

There is obviously a conservatory roof over it but I'm kinda hoping that's OK as there is no visible water

Is it worse in rainy weather, or better after a day when the sink has not been used?

When did it start happening? I would be thinking of chipping some plaster off to look at the bricks. It might be hydroscopic salts from old damp.

I'll track it over the next few days

It started about when the temp dropped & I put the heating on (I think)

Chipping off is all we can think of to do - thanks