Due to the complexity and number of the fittings and fixtures needed to install domestic systems, it is normal for the plumber to quote this trade on a supply and fix basis. However, many self-builders will want to supply their own sanitaryware and perhaps the boiler.
Cold water is supplied directly into your home from the mains via a stopcock positioned within the highway. The supply must be at least 600mm below ground to avoid frost and, it is brought up within the house to the most convenient stopcock position, usually below the kitchen or utility room sink. The groundworker will bring the drainage pipes up through the oversite. The plumber then takes over and takes the soil and vent pipes up to connect to the domestic wastewater outlets.
The plumber is also responsible, in conjunction with the roofer for the vent pipes and skirting through the roof and for any necessary leadwork to the roof, liaising with the bricklayer for any pointing.
The plumber will usually be responsible for the installation of any gas piping. Plumbers installing and commissioning gas fired systems must be CORGI (Council for Registered Gas Installers) registered. Plumbers installing and commissioning oil-fired systems should be OFTEC (Oil Firing Technical Association) registered. The plumber is usually responsible for the fitting of guttering and downpipes, once the facias are decorated, liaising with the roofers and groundworkers.
Vented and Sealed Heating Systems
Most of the older housing stock has a vented system, which employs storage and header tanks in the roof that take up any expansion as an overflow and top up and return water to the system. Most new homes are now built with a sealed system delivering hot water to the tap at mains water pressure.
These systems do away with the need for tanks in the loft and instead, any expansion is taken by an expansion vessel connected to a hot water cylinder that is capable of storing hot water under mains pressure.
Hot Water Cylinders
Many homes have an indirect hot water cylinder where the hot water within the primary system from the boiler passes through a coil or heat exchanger within the tank, which in turn heats the main body of water. This 'secondary' water is then drawn off to the tap. An alternative is the 'thermal store'. Here the main body of water within the cylinder is heated by the boiler and cold water, passing through a coil, is heated up to provide mains pressure hot water.
- Make sure that the ducting, if not the water supply piping is set through the oversite. If it is convenient to do so, a temporary tap can be put on the end to act as a standpipe for the build until such time as the proper stopcock is installed.
- Ensure all plumbers dealing with gas piping or boiler installation are CORGI registered.
- The plumber should be on site as soon as the roof is weathertight in order to notch out the top of the joists and lay the carcassing pipework prior to the floor decking going down.
- Make sure that you order sanitaryware and kitchen units in good time so as not to delay the trades.