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A domestic water system or 'DWS' is a comprehensive term for a water system in a home (domicile), non-industrial. Potable water may be supplied from a municipal water supplier by pipe line, delivered by truck or collected (filtered)from rainwater, stored in a water tank. The domestic water system consists of: a water supply, distribution system ie. piping/plumbing, and a waste water(sewage removal) removal system.
Domestic water systems have been around since the dawn of time when the first thinking man located his home 'domicile' next to a water supply, stream, lake, etc.
Water systems serve residential (domestic), commercial, institutional, hospitals, schools, and industrial appliations.
The fresh water system side of the system delivers clean, safe, potable water to each point of distribution in the 'DWS'. It is imperative in the design that the clean water is not contaminated by the waste water (disposal) side of the process.
The waste water side of a water system, should provide a means of connecting to and removing waste water from the plumbing system. Sanitary, drainage, waste and vent systems are required to be physically isolated from the supply side through the use of approved air gaps, air breaks and backflow preventers in order to physically isolate and enforce this separation between the supply fresh water and waste removal systems.of these are:
- An isolation valve must exist between the water source (say from the city) and the fixture (sink faucet)
- beyond the isolation valve, it is common for sinks to use flexible hosing from the pipes to the fixture, and more permanent fixtures (showers, toilets, etc) to use rigid piping. It is undetermined whether such flexible hosing is acceptable for in-wall piping, assuming it's located after an isolation valve (say for a shower faucet).
Waste/sewage removal
For homes attached to a munincipal water system, the waste/sewage removal system is also provided. In these cases there is, simply, another set of piping which transfers the waste water to a Waste water treatment facility or natural waste site (Usually a body of water or river) away from inhabited areas. Where the house has an independent water system, the Waste/Sewage removal is usually accomplished by means of a septic system.
Cold water supply
Most modern western water systems are directly fed from a municipal water system by a high-pressure pipe, usually located under the road or street. Many houses still use a cistern or a well where convenient water supply is not available; a pump and pressure tanks are used to maintain system pressure. Older houses (or houses that need gravity fed cold water, i.e. for a power shower) may also have a cold water tank. In such a case, drinking water (usually the kitchen tap) is usually fed directly from the main water supply due to the risk of contamination in the cold water tank.
Water supplies
Depending on preference, location restrictions/oppurtunities and expense considerations, the source of water supplied to a building can vary greatly. Many homes are connected to a metered municipal water system, which forms the entire domestic water cycle outside of the internal Distribution system. Homes further from cities and other populated areas must form the entire cycle independently. In these latter cases, the water supply can be from wells, tapped springs or rivers, even rainwater storage. Whatever the supply, the water is almost alawys connected to the home at a single point.
Internal distribution system
The internal water distribution system forms part of the cycle. Supply water enters from the munincipal supply or, for buildings not connected with a munincipal system, another form of water supply. This supply water is piped to various taps, fixtures, and appliances. The drainage from these taps, fixtures, and appliances exit through the sewage drain system.
Cold water supply system
Any external water supply is almost always a cold water supply. The Cold water supply system may include filter or water softner appliances and fixtures. This cold water is then fed to other fixtures, taps, and appliances that require cold water, such as sinks, hot water heaters, faucets, bathtubs, showers, toiletts, etc.
Hot water supply system
Domestic hot water is provided by means of water heaters, appliances intended to provide a hot water supply by heating a volume of water supplied by the Cold water supply system. The hot water from these systems is then piped to the various fixtures, taps, and appliances that require hot water, such as sinks, bathtubs, showers, washing machines, etc.Taps, fixtures, and appliances
Everything in a building that uses water falls under one of the categories; Tap, Fixture, or Appliance. These devices all serve some function in the home, or they wouldn't exist. They are the loads on the system. By performing their function, most produce some form of waste/sewage which is removed by the sewage drain system.
Taps are water outlets without an accompanying fixture.
Fixtures are devices that use water without additional source of power.
Appliances are devices that use water coupled with an additional source of power. Each connection to these (residential appliances) incorporates a backflow prevention principle of some form. See cross connection control & backflow prevention for an overview of backflow prevention methods and devices currently in use, both through the use of mechanical and physical principles.
Waste water drain system
The waste water from the various appliances, fixtures, and taps is transferred to the waste and sewage removal system via the sewage drain system. This system consists of larger diameter piping, water traps, and is well vented to prevent toxic gases from entering the living space.
Materials
In old construction, lead plumbing was common. It was generally eclipsed toward the end of the 1800s by galvanized iron water supplies which were attached with threaded fittings. Copper with soldered fittings became popular around 1950, though it had been used as early as 1900. Plastic supply pipes have become increasingly common since about 1970, with a variety of materials and fittings employed.Galvanized iron supply pipes are commonly found with interior diameters from 1/2" to 2", though most domestic systems won't require any supply pipes larger than 3/4". (Note that iron is also often used in drain/waste/vent, see the section on drain pipes.) Pipes have NPT ("National Pipe Thread") standard threads, which mate with inside threads on elbows, couplers and other fittings. Galvanized iron (often known simply as "galv" or "iron" in the plumbing trade) is relatively expensive, difficult to work with (due to weight and requirement of a pipe threader), and suffers from a tendency to obstruction due to mineral deposits forming on the inside of the pipe. It remains common for repair of existing "galv" systems and to satisfy building code non-combustiblity requirements typically found in hotels, apartment buildings and other commercial applications. It is also extremely durable.
Copper pipes were introduced in about 1900, but didn't become popular until approximately 1950 (depending on local building codes). (Note that some copper and brass are also used as drain/waste/vent pipes; for those applications, see the section on drainage systems.) Common classes of copper plumbing tube are "Type K", "Type L" and "Type M"; Type "M" is relatively inexpensive and relatively thin-walled and generally suitable for residential use, with a correspondingly lower water working pressure WWP, Type "L" has a thicker pipe wall section, and is more often used in commercial above-ground applications, Type "K" has the thickest wall section of the three types of pressure rated tubing and is commonly used for underground burial, with a suitable corrosion protection coating or continuous polyethylene sleeve as required by code. Types "M" and "L" are generally available in both hard drawn "sticks" and in rolls of soft annealed tubing, Type "K" is usually only available in hard drawn quantities of 20'-0" "sticks". The OD of plumbing tube is 1/8" larger than the nominal diameter because early plumbing tube had a standard wall thickness of 1/16". When better metallurgy made thinner walled tube possible, the OD was preserved to avoid changing the design of fittings.
| Nominal Size | OD in inches | ID in inches | ||
|---|---|---|---|---|
| Type K | Type L | Type M | ||
| 3/8 | 1/2 | 0.402 | 0.430 | 0.450 |
| 1/2 | 5/8 | 0.528 | 0.545 | 0.569 |
| 5/8 | 3/4 | 0.652 | 0.668 | 0.690 |
| 3/4 | 7/8 | 0.745 | 0.785 | 0.811 |
| 1 | 1-1/8 | 0.995 | 1.025 | 1.055 |
| 1-¼ | 1-3/8 | 1.245 | 1.265 | 1.291 |
| 1-½ | 1-5/8 | 1.481 | 1.505 | 1.527 |
| 2 | 2-1/8 | 1.959 | 1.985 | 2.009 |
| 2-½ | 2-5/8 | 2.435 | 2.465 | 2.495 |
| 3 | 3-1/8 | 2.907 | 2.945 | 2.981 |
Generally, copper pipes are soldered directly into copper or brass fittings, although compression or flare fittings are commonly used by residential plumbers. Formerly, concerns with copper supply pipes included the lead used in the (50%tin-50%lead)solder at joints. Some studies have shown significant "leaching" of the lead into the potable water stream, particularly after long periods of low usage, followed by peak demand periods. In hard water applications, shortly after installation, the interior of the pipes will be coated with the deposited minerals, which had been dissolved in the water and therefore the vast majority of exposed lead would be prevented from entering the potable water. Building code requirements often require lead-free solder for copper and brass. Building Codes throughout the U.S. require the use of virtually "lead-free" (<.2% lead) solder or filler metals.
Plastic pipe is in wide use for domestic water supply, waste or vent pipe, Polyvinyl choride PVC, chlorinated polyvinyl choride CPVC, polypropylene PPThese materials must be proven by UL testing to meet or exceed the maximum flame spread rating of 25 and maximum smoke developed rating of 50 when tested in accordance with ASTM E84, also applicable UL and NFPA standard test methods. PVC/CPVC - rigid plastic pipes similar to PVC drain pipes but with thicker walls to deal with municipal water pressure, introduced around 1970. PVC should be used for cold water only, CPVC for hot and cold. Connections are made with solvent cements.
- PBT - flexible (usually gray or blue) plastic pipe which is attached to barbed fittings and secured in place with a copper crimp ring. The primary manufacturer of PBT tubing and fittings was driven into bankruptcy by a class-action lawsuit over failures of this system.
- PEX - extruded high density polyethylene system with mechanically joined fittings employing barbs and crimped steel or copper fittings.
- Polytanks - Tanksysems made by Amprotec, polyethylene cisterns, underground water tanks, above ground water tanks, these are linear polyethylene potable water storage tanks provided in white, black or green, approved by NSF and made of FDA approved materials
- Aqua - made by Ipex, aluminum pipe sandwiched between layers of PBT and connected with brass compression fittings. In 2005, a large number of their fittings were recalled.
Regulation and compliance
- Consult local construction codes and obtain requistite permits prior to construction.
- Fire codes, local fire codes should be integrated in the design phase of the water system to prevent "failure comply with regulations" notices. In many areas of the USA, water reserves are required by law.
"Domestic water system"