ISO/TR 24524:2019 pdf download – Service activities relating to drinking water supply, wastewater and stormwater systems – Hydraulic, mechanical and environmental conditions in wastewater transport systems.
4.3 Usage patterns The frequency and nature of the usage of toilets varies considerably. Some of these uses will involve faecal material and urine with or without toilet paper, others involve urine alone (with or without toilet paper). The sequence of these uses in any one day will depend on the region, the number, gender and age of the persons in the building and the nature of the buiding. 5 Drain lines ; 5.1 General There are a range of drain line configurations found in different parts of the world (see Table 2)]. Drain line design, configuration, construction and maintenance may impact the ability of waste to pass through the drain line. Typically, material introduced into a drain line moves along the drain line with water from toilet flushing. Failure of flushed material to exit the drain line may result in blocked plumbing and the generation of unacceptable odours or allow material to dry out and adhere to the pipe surface. When material moves down the drain line it may occasionally become snagged on a damaged or broken pipe. Depending on the severity of the damage to the pipe, it should then either self-release, tear off the snag or break up within a certain number of flushes. When such material does not release, tear off or break up, it may result in issues for the drain line. Any material discharged via a toilet should not adversely affect the intended operation of the drain line or sewer system. It should exit a drain line within a timeframe/number of flushes.
5.2.3 Drain line clearance一settling The first consideration for drain lines with intermittent flow conditions is whether or not the discharged material will exit the drain line by the simple action of being carried by the flushing water. The weight of some discharged material can increase due to oversaturation with water resulting in it becoming too heavy to move. When this occurs, it is often referred to as settling. With regards to a toilet flush, the flushing water is separated into two categories: the water which precedes the discharged material and wets the drain line ahead of the discharged material (which reduces friction) and the water which follows the discharged material and creates a hydraulic force pushing the material down the drain line. In most cases, the water surrounding the discharged material passes around and moves ahead of the discharged material. The solid will then settle on the lower surface (invert) of the drain line, until moved along by the next flush – the forces exerted by successive flushes being less as the solid gradually gets further from the discharge point. Further, additional sources of water will also typically be present in the drain line along with water from toilets. These additional flows may provide some additional transit to any solids which remain stationary in the drain line following a toilet flush. Settling is related to the nature of the discharged material, the volume of the flush, the velocity of the flushed water, the pipe gradient, the length of drain line/distance from discharge point, and the design and installation of the drain line (including size, angle, length, construction material and joint design).
ISO/TR 24524:2019 pdf download – Service activities relating to drinking water supply, wastewater and stormwater systems – Hydraulic, mechanical and environmental conditions in wastewater transport systems
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