The Cold Water Supply

From the rising main stoptap, the main cold supply pipe rises up through the house (which is why this stoptap is so named). Installation of a stop is a job for a qualified plumber. A branch pipe is always connected to the rising main to supply the kitchen cold tap with a pure supply of water for drinking and cooking purposes. There may also be branches off this pipe serving a washing machine or dishwasher.
Indirect systems In the majority of homes the rising main then continues upwards to supply a cold water storage tank in the loft or in an upstairs cupboard. The flow of water into this tank is controlled by a ball valve. As water is drawn off, the valve’s float arm drops which opens up the valve to admit more water. The valve closes again when the tank is Filled to the correct level.
This tank then supplies cold water to the rest of the house. Normally there will be two feed pipes running from near the base of the tank; one will supply all the cold taps (except the kitchen) and also WC cisterns. The other will supply cold water to the hot water cylinder. Both pipes should be Fitted with an on/off control called a gate valve, which allows the feed to be isolated if necessary.
If the house has a conventional ‘wet’ central heating system with water-filled radiators, there will be a second, smaller tank in the loft which is supplied by a pipe which branches off the rising main and again which is fitted with a ball valve. This is the heating system’s feed-and-expansion tank. Its purpose is to accommodate the expansion in the system’s water content as it heats up, and also to replace any losses from the system should they occur. There should be a stoptap on its
WATER SUPPLY BY-LAWS The water supply to every home is subject to the various provisions of the water supply bylaws. These exist to prevent waste, undue consumption, misuse or contamination of the water supply. Under the by-laws, you are obliged by law to give five working days’ notice to your water authority if you propose to install or alter (as opposed to repair or replace):
• a bidet
• a flushing cistern
• a tap to which a hose may be connected
• any fitting through which
contamination by back-siphonage could occur
In Ireland you must give notice if you propose to install or alter any water fitting.
Notice must also be given if you intend to bury a supply pipe underground or embed it in a solid wall or floor
Plumbing, Heating and Waste Systems
branch supply pipe to enable you to turn off its water supply if necessary.
Direct systems – Some homes have a direct cold water supply, with branches to taps and WC cisterns taken directly from the rising main. Hot water may be supplied by a multi-point water heater, by a conventional hot cylinder containing an immersion heater, or by a gas or electric storage water heater. Alternatively, there may be a full-scale central heating system which also supplies hot water via a hot cylinder.
Direct plumbing systems may be easier and cheaper to install, but most water authorities prefer indirect systems (and nowadays may not allow direct ones to be
installed). One of the main reasons for this is that indirect systems make it very difficult for the mains supply to be contaminated by back-siphonage of dirty water if there is a drop in mains water pressure. This subject is very much to the fore in the current water supply by-laws, and which will be mentioned at intervals throughout this book. Indirect systems are also convenient for the householder, because they guarantee a supply of stored water in the event of an interruption in the mains supply, and they are also quieter in operation than mains-fed systems.

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