Hot Water And Oil Boiler System

The Hot Water System

As with cold water systems, there are two basic types of hot water system. In one, the water is heated and stored ready for use, while in the other it is heated as it is required.
Storage systems Cold water is supplied (usually from the loft storage tank) to a copper cylinder, where it is heated and is then piped on to feed the hot taps around the house. The heating may be by means of an electric immersion heater set in the top of the cylinder, or else by a separate boiler. On older direct systems, water flows from the cylinder to the oil boiler service and back again, usually relying on gravity for its circulation (warm water is lighter than cold water and so rises and drives the water round the system).
The cold supply pipe and the feed to the boiler are connected near the base of the cylinder, and the boiler return pipe is connected near the top. The hot water take-off is from the domed top of the cylinder, and a vent or warning pipe runs up to the loft where it discharges over the cold water tank in the event of the system overheating. This system is not used nowadays because the constant intake of fresh water causes serious scale build-up within the boiler and cylinder.
On indirect systems, there is a copper coil inside the cylinder through which circulates water heated by the boiler. The water in the cylinder is heated indirectly by the hot water in the coil; the two never mix so scale build-up in the boiler and coil is minimal. It still occurs on the outside of the coil, but this is less of a problem except in areas with extremely hard water.
Such a system has an additional cold tank in the loft — the feed-and-expansion tank mentioned earlier. Where the boiler also supplies the central heating system, the circuit to the cylinder may rely on gravity for circulation, but on newer systems it is usually pumped.
Instantaneous systems Where it is not feasible to have a cold water storage tank or hot cylinder (typically in flats), some form of instantaneous water heating is usually provided. This may be a gas-fired multi-point water heater (supplying hot water only) or a combination boiler which also supplies the central heating.


Heating Systems

Mention has already been made of boilers supplying central heating as well as hot water, and the vast majority of homes with central heating have this type of system. The circulation from boiler to radiators is driven by a pump, and on more sophisticated systems, motorized valves control the distribution of hot water to the hot cylinder or the radiators as directed by the system controls.

Waste Water Systems

Getting rid of all the waste water a house produces is generally much simpler than supplying it in the first place since you can rely on gravity to do the job for you.
Two-pipe waste system These are generally found in older homes. Here the
WC waste runs to a large-diameter soil pipe which runs down the outside wall of the house and which is connected directly to the underground drains at a manhole or inspection chamber. The soil pipe also runs up to roof level, where it is vented to the open air.
Waste water from other upstairs appliances runs to a hopper mounted on the outside of the house wall. It then goes via a downpipe to a gully at ground level and on to the drains via a separate underground pipe. Waste water from downstairs goes direct to an open gully and then via another branch to the drains. Rain-water downpipes often also discharge into the same drains.
Single-stack waste system These are found in newer homes. Here a single soil pipe collects waste from all the water-using appliances in the house and takes it direct to the underground drains. This soil pipe is again usually vented to the open air at roof level, but may be capped inside the house with a special pressure relief valve in certain circumstances. There may also be gullies at ground level to take waste from appliances remote from the soil stack, but the waste pipes discharge into them below the level of a gully grid instead of over it. Rain-water down-pipes are no longer connected to the foul-water drains, but run either to separate surface-water drains or to soak-aways.
The twin advantages of this single-stack system are that all the pipework can be concealed within the house, and that it does away with open discharges at gullies and hoppers which lead to smells and blockages. However, they must be designed carefully if they are to work properly, and there are strict rules about where connections can be made into them.
The most important feature of any waste water system is that it must not allow drain smells to enter the house through the waste pipes. All waste systems do this by having water-filled traps connected to every water-using appliance for built in in the case of WC pans), and these are designed so that they retain the water seal as the appliance is emptied. On modern single-stack systems the trap should always be the deep-seal type, with a water depth of 75mm (3in).
The soil pipe and any branch pipes from gullies run underground from the house and link up at a manhole. This will
be a brick-built chamber on older properties, or a smaller plastic one on newer ones. From there a single drain carries the combined wastes to the main sewer, which generally runs beneath the road next to the property. Additional manholes are provided wherever the drain run changes direction, and on older properties the final manhole may contain a trap and a capped-off rodding eye — this is known as an interceptor trap, and is designed to prevent sewer gases and rats from entering the system. Such a trap is not needed on modern drainage systems.
A few rural properties remote from mains drainage may have a cesspool or septic tank to dispose of waste water. A cesspool is just a watertight underground chamber which retains sewage and waste water until it can be pumped out and disposed of by a special tanker — a job that has to be carried out regularly. A septic tank is in effect a miniature sewage works, encouraging the decomposition of stored sewage through the action of anaerobic bacteria so that harmless effluent can then be discharged safely into a stream, ditch or land drain.

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.