{"id":140,"date":"2022-05-18T18:30:44","date_gmt":"2022-05-18T22:30:44","guid":{"rendered":"https:\/\/opentextbc.ca\/plumbing3b\/chapter\/describe-sizing-for-the-building-water-supply-system\/"},"modified":"2022-09-07T11:49:19","modified_gmt":"2022-09-07T15:49:19","slug":"describe-sizing-for-the-building-water-supply-system","status":"publish","type":"chapter","link":"https:\/\/opentextbc.ca\/plumbing3b\/chapter\/describe-sizing-for-the-building-water-supply-system\/","title":{"raw":"Learning Task 2","rendered":"Learning Task 2"},"content":{"raw":"The proper sizing and installation of potable water distribution systems in residential and small commercial applications is critical to proper operation of the plumbing fixtures and equipment installed within the building. The potable water system must be capable of meeting the peak water supply demands<\/em><\/strong> of the connected fixtures and appliances. Each fixture or appliance requires a minimum supply pressure<\/em><\/strong> and flow rate<\/em><\/strong>; if the system fails to maintain these conditions, the fixture or appliance may not adequately perform its intended function. An undersized cold water pipe to a washroom group of fixtures could lead to an excessive pressure drop<\/em><\/strong> upon operation of a water closet, which could lead to an adjacent shower valve suddenly being starved of cold water, which could lead to scalding. Similarly, an excessive pressure drop due to flow to other fixtures could lead to a flush valve fixture failing to function properly.\n

Terminology<\/h1>\n

Peak Water Supply Demands<\/h2>\nEach fixture, device, or appliance is given a fixture unit value, referred to as a water supply fixture unit to differentiate from DWV fixture units. The peak demand flow is the total of all the fixture unit values if all fixtures were used at once, including any additional load for a fire sprinkler system, irrigation system or any other demands on water service.\n

Minimum Supply Pressure<\/h2>\nEvery building water distribution system will have one fixture that requires more pressure than the others to operate correctly. This fixture is referred to as the \u201cgoverning fixture.\u201d The BCPC Sentence 2.6.3.1. (1) states that the \u201cwater distribution systems shall be designed to provide peak demand flow when the flow pressures at the supply openings conform to the plumbing supply fitting manufacturer\u2019s specifications.\u201d This means that the plumber must determine the minimum pressure required for the governing fixture by using the manufacturer\u2019s specifications.\n\nIn past BC Plumbing Codes, the minimum pressure for common fixtures was listed on Table 2.6.3.2.-A along with the fixture unit load. In previous codes, fixtures such as clothes washers, dishwashers and direct flush valves required a minimum flow pressure of 15 psi (approximately 105 kPa) at the fixture to operate properly. Therefore, when the manufacturer\u2019s specifications cannot be used \u2013 because the make and model of the fixture are unknown, for example \u2013 the plumber should still use 15 psi (approximately 105 kPa) when calculating water pipe sizing.\n

Pressure Drop<\/h2>\nPressure drop in a water supply system is difference between pressure at the upstream end of a pipe and the pressure delivered to a fixture of device. Pressure loss will occur in water pipe due several factors, including:\n