Plumbing and drainage drawings in Islington

Basements, terraces and building over old drains

The borough's Basement Development SPD covers the digging and drainage issues of basement work, and those need settling early. A terrace here usually has a shared drain along the rear, a sewer below the street and little room between them. Approved Document H asks for special care when building within 3 metres of a drain's centreline.

A pipe should not pass under a building for more than 6 metres, and building over is not advised where the drain is deeper than 3 metres or larger than 225 millimetres across. Our drawing marks the drain, the offset to the new wall and the protection proposed, which is what the water company's engineer needs to see.

Basements also raise the pumping question. A basement bathroom below the sewer level needs a pumped outlet with an alarm and a non-return valve, and the drawing shows the chamber, the rising main and the point where it joins gravity drainage.

Falls, water use and connections

Foul drains need a minimum gradient: a one-hundred-millimetre pipe may run at 1 in 40 where peak flow is under one litre per second, and at 1 in 80 (minimum 1 WC) above that. In a terrace with a shallow existing drain, the fall is often what decides where a new bathroom can go.

New dwellings must meet a water-use standard under the Building Regulations of 125 litres per person per day, or 110 where the optional requirement applies. Islington's own limit is lower, so our fittings schedule is specified to the council figure. The bath outlet is limited to 48 degrees Celsius.

A connection to a public sewer needs a notice, to which the sewerage undertaker has 21 days to respond.

How we draw a basement bathroom in a terrace

Picture a lower-ground bathroom in an Islington terrace. The outlet sits below the street sewer, so the waste must be lifted. We draw the pump chamber, the rising main to a high-level connection and a gravity drain beyond it, with the vent routed to a point on the rear elevation the heritage officer can accept.

The hot and cold supplies follow, with isolation valves in reach and the cylinder or heat source marked. Every pipe is labelled with its size, and the sheet notes what the plumber must test before the finishes go on.

A borough of flats, heritage and party walls

Only 16.3 per cent of households live in a house, and 26.7 per cent own their home, so many jobs involve a flat in a converted building, with drains shared between floors. Islington holds 41 conservation areas and 1,050 listed building entries, which limits where a new soil stack or vent can rise on an elevation.

Digging near neighbours can trigger the Party Wall etc. Act: excavation within 3 metres of a neighbouring building and deeper than its foundations, or within 6 metres where a forty-five degree line crosses the work. Our party wall notices service covers the paperwork.

The set sits within your building regulations drawings in Islington and construction drawings. The plumbing and drainage drawings hub and the electrical design drawings in Islington page cover the neighbouring services.