New plumbing installations in your home

Water runs downhill, so a new sink, shower or WC needs a waste pipe with a steady fall to a drain or soil stack. The further the new appliance sits from the existing drainage, the harder that becomes: long horizontal runs need depth to keep their fall, and a WC needs a large-diameter connection to the soil stack. A plumber will usually look at where the stack and drains are before anything else.

Where gravity cannot work, for example a basement WC or a shower below the level of the drain, a pumped system or macerator is the alternative. They are useful, but they need electricity, maintenance and a suitable model for the appliance, and they are not a substitute for proper drainage where proper drainage is possible.

The supply side is simpler but still matters. Check the pressure and flow of your system before choosing taps and showers; some mixers need mains pressure and perform poorly on a low-pressure gravity system fed from a loft tank.

Adding a WC, bathroom or kitchen in a new position usually involves new drainage and often new ventilation, which fall under the Building Regulations for drainage, sanitation and ventilation. Ask the plumber at the quote stage whether Building Control needs to be notified and who will do it; a new bathroom without approval can cause questions when you sell.

Water fittings in England and Wales must meet the Water Supply (Water Fittings) Regulations 1999, which aim to prevent contamination and waste. For a new outside tap, that means protection against back-siphonage, so water from a hose left in a bucket or pond cannot be drawn back into the drinking water supply. Certain installations, such as a large bath or a pump drawing directly from the supply pipe, have to be notified to the water company before work begins. Scotland and Northern Ireland have their own equivalent rules.

Source: legislation.gov.uk

A cloakroom WC under the stairs often fails on ventilation or on the distance to the soil stack, not on the space itself. A utility room in a garage needs frost protection for pipes and a waste route through or under the garage floor. A kitchen island sink needs its waste run under the floor, which is straightforward in a new floor and disruptive in an existing one. Moving a kitchen sink to another wall may mean a new connection outside to a gully or drain.

For washing machines and dishwashers, the plumber fits isolating valves and a proper waste connection with a trap, so smells and backflow from the sink are avoided. Ask for valves you can reach without pulling the appliance out.

• what you want to install, and exactly where, with a photo or sketch
• where the nearest soil stack, drain or gully is, inside and outside
• your hot water system: combi boiler, cylinder, unvented cylinder
• floor type: suspended timber or solid concrete
• who supplies the sanitaryware and taps
• whether tiling, boxing in and making good are wanted in the price

Choosing the position first and asking about drainage later; buying taps that do not suit your water pressure; fitting non-compliant fittings bought cheaply online; leaving new pipework without access points or isolation valves; and not planning where the boxing in will go before tiling. Each of these is cheap to solve on paper and expensive once the room is finished.

Describe the installation and confirm your mobile number and email. Plumbers near you see the job without your name or contact details, and one of them can buy it, after which it is no longer offered to anyone else. The plumber pays Offrano; you do not.

Before your details are shared, we email you the plumber's name, address and phone number. No plumber is obliged to buy the request, and it is withdrawn after 21 days if nobody does. Offrano only confirms that buyers are registered businesses, so ask whether the plumber belongs to an approved contractor scheme for water fittings, and who handles Building Regulations.