A detailed floor plan of your house, on which are marked the existing water supplies and the drainage services, will help you to determine where you are going to site new plumbing installations. The diagram on this page and the one opposite represent the ground and first-floor plans for a typical semi-detached house, with two living rooms and a kitchen on the ground floor, and a bathroom and three bedrooms on the first.
Extending the water supply pipes to the new fittings should present you with few problems; careful planning will be necessary, though, to ensure that the fittings are correctly plumbed into the drainage system. The drainage services from the kitchen sink and from the first-floor bathroom. Pipework that is in white indicates where waste pipes would be needed for the addition of a shower in either of the two bedrooms or in the cupboard underneath the stairs; or for the addition of a wash basin, in this case, a vanity unit, which is a basin set into the top of a low cupboard—in the bedroom adjoining the bathroom. The waste system can be the old two-stack variety, with the bath and basin waste discharging into a hopper head and the W.C. directly into a separate cast-iron soil stack.
When you make the sketch plans of your floors, include the positions of existing plumbing appliances and services, and of possible obstructions to new pipework. Do this plan to scale, adding all the dimensions; you will then be able to tell whether or not the proposed new appliance will fit, and can estimate for materials such as copper piping for extending the supplies, and plastic pipes for the wastes. In new houses, builders‘ plans are usually available from the agent that negotiated the sale. Decide on the type of appliance to be added, collect information about its dimensions, choose the optimum position, and lightly sketch in the appliance on your floor plan.
Next, work out the availability of the necessary services. Maybe the water supplies can be extended with only short runs of extra pipe, but you realize that the drain is inaccessible; in that case you will have to work out another position for the appliance. A well-made diagram will readily provide such information. When designing new plumbing services, try to site the appliance as close as possible to the main stack: long runs of waste pipe are undesirable for many reasons.
Blockages are more likely to develop in long runs than in short ones, especially in those that have to change direction in order to by-pass obstructions; noise, created by frictional resistance as water travels through the pipe, may occur; and venting will often be necessary. For example, a 40 mm diameter waste pipe from an installation to a single stack system (combined waste and soil stack) should be vented if its length is more than 2.3 metres.
If you cannot avoid a long run, make sure that you install cleaning eyes at regular intervals and wherever the pipe changes direction. Increase the diameter of the pipe to reduce noise. And if venting is impracticable, you must fix a special resealing trap to the appliance. The plan should also allow a sufficient downward gradient of the pipe towards the drainage services. For a 40 mm diameter waste the minimum desirable slope is approximately 1 in 50, that is, 20 mm per metre. If the fall is insufficient, the emptying of waste water from the appliance will be sluggish, again causing blockages.
Conversely, if the fall is too great, the appliance will empty too quickly, which may result in the trap seal being removed by differential pressures. If you have any doubts, niake a sketch plan of your project and take it tq your local water authority who is very willing to offer help and advice. In any case, the water authority should always He (consulted before you embark on any major alterations to the sanitary fittings in the home.