Plumbing and drainage drawings in Lambeth

Flats, shared stacks and who owns the drain

Only 24.8 per cent of Lambeth's 134,688 households live in a house or bungalow. Most of the borough is flats and conversions, and that changes the drainage brief. A soil stack often serves several dwellings, a basement bathroom may discharge below the sewer level, and a kitchen move can mean a new branch into a shared vertical stack.

Before any line goes on the sheet we establish ownership. Many drains that once belonged to a row of houses passed to the water company on 2011-10-01, so a connection or a diversion usually means a notice to the sewerage undertaker, which has 21 days to respond to a proposed connection. We prepare the plan; you or your contractor submit it.

A flat conversion in a Victorian terrace brings its own test. The drawing must show where each new kitchen and bathroom drains, the fall of the horizontal run, and whether a pumped outlet is unavoidable. Our flat conversion drawings service coordinates the layout so the services follow the floor plan rather than the other way round.

Heritage and trees limit where pipes can go

Lambeth has 64 conservation areas and 12 Article 4 directions, and its list holds 953 entries. Those numbers matter for plumbing more than most owners expect. A new soil vent pipe on a front or side elevation can be a visible change that needs consent where a direction applies.

We therefore try to run new stacks internally, up through a chase or boxed corner, and terminate the vent on a rear slope. Where that is not possible the drawing shows the external route in elevation so the planning officer can judge it. For a listed house the pipe route is a matter for listed building consent and is drawn with that in mind.

Trees are the other limit. The borough holds 339 tree preservation orders, and a new drain trench cut near a protected root zone can be a problem. We mark the trench line and its distance from nearby trunks so the arboricultural question is raised early.

The national figures behind the sheet

Approved Document H sets the fall of a foul drain. A one-hundred-millimetre drain carrying under one litre per second of peak flow can be laid at 1 in 40, which is why a shallow Lambeth terrace drain often limits how far a new bathroom can sit from the stack.

Where an extension crosses a public sewer, the guidance looks at work within 3 metres of the pipe centreline. A line passing under the new structure should not have more than 6 metres of its length beneath it, so we measure that on the survey before the foundations are drawn. For the full national picture, see our plumbing and drainage drawings guide.

Fixed quote, scope and checking

We do not publish a starting price for this service because a bathroom move and a basement drainage scheme are different amounts of work. You send the address, we run a free constraints check, and you get a fixed quote.

We draw and specify. We do not install, test or certify the system. A second chartered technologist, never the person who drew the sheets, checks every set before it leaves us, and redrawing after an officer's comment is free until approval. For context on the borough as a whole, read architectural drawings in Lambeth.