What is this duct thing in my house?

[IRunLikeJoeBiden]

This boxed in duct thing runs floor to ceiling in the under stairs toilet. It’s about 6 inches x 4 inches. Nothing seems to connect to it.

Forgot to say, there’s boxing in the room above of the same size, in the same place, which goes up through the ceiling of that room, so I’m thinking whatever it is, it runs the full height of the house.

Is it the soil pipe from the downstairs toilet ?

Heating pipes?

@Chumleymouse

Is it the soil pipe from the downstairs toilet ?

yes, it is the duct containing the soil pipe. Typically it runs from the ground (where it goes off towards the sewer) and up in the corner of the downstairs WC or the kitchen, then up in the corner of the bathroom (where it connects to the WC and also the bath and basin wastes) and then (preferably) up through the loft to emerge into the open air above the height of your windows so it can ventilate into the air.

In some cases is it sawn off in the bathroom and instead of ventilating outside, it has a nominally one-way air valve, which stinks when it jams (as it will).

Thanks, duct detectives!

Is there any reason why I can't build a stud wall in front of the one in the bathroom upstairs to bring the wall out level?

apart from wasting space, you mean?

A plumber might need access to it one day.

How about a 100mm deep wall cabinet?

It’s right where I want to put the bath in the upstairs bathroom, so I was wondering about bringing the wall forward and doing a bath/shower niche type thing.
Wonky scale drawing attached!

it's unusual to have two so close together.

is there an extension on the house?

Wouldn’t it be better to move it into the corner? Then you can just lose a bit of space on the narrow side of the bath.

No extension. The one at the top left of the pic is for the toilet that is in the upstairs bathroom. The one at the bottom right of the pic is the mystery duct that comes up from the downstairs toilet.
If it is a soil stack, how easy is it to move?
Unfortunately we’re currently using the downstairs toilet as a storage room so I can’t look at the bottom of the duct but I don’t think the toilet connects to it.

Climb into the loft and see what comes out of the top of the duct. Photos if unsure.

Presumably you have no cellar below the downstairs WC?

Nothing below the downstairs toilet, no. It’s the annual trip into the loft for the Christmas decorations at the weekend so I shall investigate then. And report back, of course, because I’m sure this is very exciting for everyone.

Defo check it out. It might be redundant and you could get rid of it.

You can remove part of the boxing, as well as going into the loft to check.

Are you in a house or flat?

I know you said you have an upstairs but so do some flats.

It‘a a house, about 20 years old so I doubt it’s become redundant over time through refurbs etc.

What are the air vent things for, do you think?

air vents are a bit suspicious. If it is a plumbing duct, the pipes inside should not be leaking so it should not be damp.

If it had a flue or chimney inside, I wouldn't expect it to be made of (as it seems) wood. There is an extractor fan nearby, but not positioned as if the extract duct was in the boxing.

It is much larger than would be normal for a water pipe or electrical cables.

Next to a WC, and that size, would be normal for a soil pipe.

It will be interesting to see what you discover in the loft.

@PigletJohn what tradesman do I need to approach to move a soil stack...

@RandomMess

You don’t want to move a soil stack unless you really have to.

You’ll need a plumber and perhaps a builder if you need to excavate and build a new manhole etc.

Put lots of niches over the bath next to it. They are so useful

@ALLIS0N

We have an internal unvented soil stack (whole street built like that) so "just" want it moved to be external, could still be reconnected back before it goes into the manhole cover but suspect we will need scaffolding is it really a plumber?

[quote RandomMess]@PigletJohn what tradesman do I need to approach to move a soil stack...

[/quote]
first find out what it is, then see if your ground floor is solid concrete, or wood with a ventilated void beneath. Most of the work would be builder.

It's possible that the whole thing is just a stink pipe for ventilation, but curious that your house would have two just a few metres apart.

@Solasum

Put lots of niches over the bath next to it. They are so useful

Yes, I wondered about this. Perhaps a full height stud wall with niche in, running between the duct and the corner (as that would be the shower end of the bath), and a half height one for either the rest of the wall or for the rest of the length of the bath, either with a niche in or just as a shelf.

@PigletJohn, it’s me who has the two a couple of metres apart, not RandomMess.

A thought, could it be for gas pipes?