We have a Victorian flat, and the grey waste exits through some iron pipework under the floor. There are two pipes running nearly parallel, one above the other (about 5.5m long). I presume the upper one serves as a vacuum breaker and as a buffer to reduce the risk of ingress of waste from the flat above.
I need to send a message to the plumber¹, and I?d like to be able to refer to this upper pipe without writing a whole paragraph, so I?m hoping that someone in the group can provide the appropriate term.
[1] as in email, rather than horse?s head left on mattress; we won?t be seeing him before he starts work on the bathroom, so I need to send him some details of the work. There?s too much of it for me to do, but I want to make sure I can maintain it myself.
The reason I ask is that IME a long run of horizontal cast iron is unusual in a purpose built flat. More normal is to have either an external or internal vertical stack(s) with short branches coming in from the adjacent kitchens or bathrooms. In the old days these branches would be lead but by not the internals will probably have been changed to plastic (usually bodge jointed into the old lead as it goes through the wall - rubber sleeve joint should be used instead)
The main stacks are called either the waste (grey water) stack or the soil (poo) stack. At the top of each of these is an open leg to supply the vacuum break you describe and this section is merely described the vent (pipe).
I can see that having the upper floors' stack passing through your property without any horizontal entries and having your grey waste join at a separate vertical joint outside is a good idea but having the pipes in that arrangement, horizontally, is so unusual that I don't think there will be special names assigned to them.
Best guess would be:
First: Grey waste from upstairs.
Second: Grey waste from this flat.
I'd suggest a sketch with these names on it and marking each pipe _very_ visibly in situ, perhaps marker on white or masking tape to avoid confusion.
The chances are he wont read the labels or the sketch but it will give you some ammunition if he ignores them and then screws up (copy/photo evidence before hand of course).
Keep notes short and sweet or they definitely wont be read.
Definitely not plastic. It could be lead, but it looks too straight for that.
This is all grey water. The horizontal pipes both exit into the same vertical pipe outside, and are joined together at the point where all the above-floor pipework runs into them.
No. The grey waste from upstairs joins the vertical external run. I wonder if I can express it in ascii art:
grey water from from above / wall / / | | X | | X grey water from our flat goes in here | | X | | | X V | | X*************floor*************| |*********************** | |_________________________________| | | _________________________________ |
Thanks for the extra info and ASCII art. Circa 1900 tenement property is where my limited experience of this is but this is not a setup I've seen before.
It peeked my curiosity though so I called a pal who is a building surveyor with experience of this era and he confirmed that it was a common configuration where long runs were concerned and the upper pipe acted exactly as you describe as a vacuum breaker.
Terminology wise, the best offering off the top of the head was 'vent pipe' for the upper. He has an old text from 1920 or so and says that he will have a look at it and will report if back if there is a better term or description.
While it's a clever idea I can see issues with the upper pipe not being regularly washed through but taking the odd splash of grey water or perhaps light debris which could either stagnate in pipe or dry on leaving a crust, leading to eventual blockage of the vent.
They were meant to ventilate the trap to avoid the water seal being sucked out, as a vacuum breaker as you've said.
They were no longer installed after the modern soil and vent system was developed by (IIRC) the BSRIA, probably in the 1950s.
However, I'd be wary of using the term, without explaining it, to a plumber; I said it was a puff pipe on some plumbing forum. I don't think any of the plumbers either believed me or had heard of it previously.
Yes, I?d thought of that. I?m sure the system wasn?t designed with the current pattern of use in mind; I suspect that there was just one sink in the flat buried in the internal space that is now the bathroom.
Thanks (and thanks to everyone else who has responded). It?s a bathroom refurbishment, and I want to discourage the plumber from cutting into the iron pipes (if they are iron) or blocking off the vent pipe, and I want access to the end of these pipes for rodding. Replacing them with plastic would be very expensive (needing a scaffold tower to get the the joints outside), so we?re hoping that the job can be done without that.
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