Step by Step Design & Calculation of Plumbing system-Part2/2

Learn how to size sanitary drainage pipework, tracing wastewater from horizontal branches to the vertical stack, then to the building drain and building sewer.

Apply a five-step method to size horizontal branches for soil and waste pipes. Learn to use trap connections, slope, and NBC table 18 fixture units for a double-stack system.

Identify drain fixture units from table 18 NBC to total 24, then select a four-inch horizontal branch pipe per table 13 ESP. Set slope at 1% per table 704.1.

Draw a rough waste pipe layout, identify trap sizes and DFUs from table 18, then size horizontal branches with table 13 and slope per table 704.1.

Size the soil stack by totaling 24 DFAS per public toilet across five branch intervals, yielding 120 DFAS, with ground floor toilets connected to the building drain.

Size the sanitary stack in the final step using fixture-unit loads and table checks across branch intervals and story counts, then select a four-inch pipe.

Apply the soil stack method to design the sanitary waste stack and pipe, with connections to the manhole or gully trap and sizing the 110 mm pipe from fixture counts.

Size building drains for soil and waste by estimating total dfus (144 soil, 138 waste) and, using a slope table with common values like 1:8, determine a 4-inch pipe.

Learn how traps prevent the backflow of air and odors by creating a water seal, acting as a non-return valve, and understand integral traps for WC, sinks, and urinals.

Explore how floor traps and nahani traps are classified by use and by shape. Learn about flow, nanny, gully, and intersection traps with P, Q, S types and a jali.

A gully trap sits outside the building. It handles waste pipe drainage in a two-pipe system and aids blockage removal and inspections, with a 50 water seal before external sewer.

Understand how intercepting traps, including deep seal traps with a 100 mm seal, protect buildings by preventing sewer gas ingress and enabling inspection of flow and blockages.

Classify traps by shape: P traps for wall outlets at 90 degrees, S traps for floor outlets, integral traps, and cue traps for space-saving use on upper floors.

Explain how interceptors—grease, oil, and sand interceptors—separate and retain fats, oils, grease, and sand in wastewater to protect the sewer.

Learn how a grease interceptor traps fat, oil, and grease from food preparation areas and sizes it by incoming flow rate and grease retention capacity using table 1003.3.5.1.

Calculate the triple compartment port sink capacity to obtain 28.05 gpm, adjust to 75% for a 21 gpm inflow, and select the grease interceptor size (£40) from the retention table.

size oil interceptors for repair garages and car washes with a minimum six cubic feet for the first 100 ft², then add one cubic foot per each additional 100 ft².

Size the sand interceptor to capture heavier-than-water solids and floating debris in stormwater before discharge to the public storm sewer, using the stormwater runoff flow rate to determine capacity.

Learn how stormwater drainage conveys rainwater from roads and buildings into the public storm sewer, distinguishes stormwater from wastewater, and explores infiltration, grey water reuse, and code-based drainage strategies.

Identify stormwater sources such as verandahs, balconies, sunshades, carports, roof spaces, and open walls. Collect rainwater with periphery channels and downpipes on flat roofs, and with gutters on inclined surfaces.

Learn to calculate stormwater runoff with the formula Q = C × I × A ÷ 16, identifying runoff coefficient, rainfall intensity, and area of catchment.

Explore how to determine catchment area for stormwater by calculating horizontal areas with 50% of adjoining walls, and include 50% of vertical elevation for slope surfaces.

Learn how to calculate catchment areas for flat surfaces with terraces and rainwater downpipes, using horizontal roof areas and 50% of vertical walls to size dp1, dp2, and dp3.

Calculate catchment area for a sloped surface using the standard formula: horizontal plane area plus 50% of vertical elevation plus 50% of the adjacent wall (roof a b c d).

Understand runoff coefficient, the ratio of runoff to rainfall on a catchment. Use surface values like roof 0.8, lawn 0.2, and asphalt road 0.8 to estimate runoff.

Explore how rainfall intensity varies by location and how catchment area and rainfall runoff coefficient influence measurements. Use a tub example to illustrate rainfall depth per hour.

Roof gutter is a narrow channel that collects rainwater from an inclined roof and directs it to the pipe, detailing external gutter, common gutter for both slopes, and parapet gutter.

Learn to design roof gutters and downspouts by calculating catchment area, rainfall runoff in gpm, and gutter size, slope, and downspout using IPC tables 1106.6 and 1106.3.

Explain primary and secondary roof drains, emphasizing the secondary as a heavy rainfall failsafe to protect roof structural integrity from blockages. Describe scooper placement and 100-unit spacing between drains.

Analyze the architectural layout of a flat roof with low slope to define seven zones; assign one drain per zone and compute flow with C×I×A, convert to gpm.

Draw the stormwater drainage layout and connect rainwater downpipes, then size horizontal storm drains via IPC table 11.06.2 and size downpipes, accounting for horizontal full-flow and vertical partial-flow.

Discharge stormwater by rainwater harvesting for non potable use and groundwater recharge, using a sand interceptor and a recharge pit, or alternatively discharge to storm sewers with an inspection pit.

Ventilation exchanges air between drainage pipes and the atmosphere to release sewer gases and admit air, maintaining balanced pressure and protecting fixture-trap seals from fluctuations.

Explore static and trap ventilation in drainage systems, detailing stack ventilation types—vent stack, relief vent, and yoke vent—and trap ventilation methods for individual fixtures, loop vents, and wet vents.

Explore trap ventilation types, including individual, unit/common, circuit/loop, and wet vent configurations, with practical implications for fixture placement and venting limits.

Size the wet vent for a private bathroom group by calculating drainage fixture units, excluding the most downstream and symmetrical fixtures, and select a two-inch vent per the IPC table.

Size the circuit vent to match the horizontal drain, half the branch size. For four inches or more, add a relief vent per IPC and connect between the uppermost fixtures.

Size vent stacks with table 906.1 IPC by evaluating developed length, soil/waste stack size, and total fixture units; example: 90 dfus on a 4-inch stack yields 2.5 inches.

Size unit vents like individual vents for fixtures at same level, minimum 1 1/4 inch; for different-level fixtures on same floor, use table 911.3 for offset and two-inch drain.

Size the individual or back vent by identifying the trap size and using the table to determine the vent size; a four-inch trap requires a 1 1/2 inch vent.

Explore drainage and ventilation in high-rise buildings, contrast primary and secondary ventilation, and introduce active drainage ventilation using a positive air pressure attenuated device and a second air admittance valve.

Understand how the positive air pressure attenuator and air admittance valve maintain balanced atmospheric pressure in drainage systems, reducing pressure and protecting trap seals with a membrane.

Learn how air admittance valves balance negative pressure to protect water trap seals, venting branch drains and preventing vacuum during flushing by admitting outside air near the trap.

Outline design guidelines for active drainage ventilation in high rises, detailing single/dual pipe systems, attenuator counts, and air admittance valves after every five floors on main stack and soil/waste branches.

Identify basement wastewater sources, including car washes, parking, fixtures, leaks, floods, and fire water. Explain why basements need pumped drainage and how sump pumps move waste to the public sewer.

Explore sump pit design: wetwell diameter minimum 18 inches and depth minimum 24 inches, and calculate volume with v = t × q / 4 plus 10–15% for the pump.

Compare sump pumps and ejector pumps to learn which is built for non sanitary wastewater in unfinished basements and which handles sanitary waste in offices and bathrooms.

Design a cylindrical sump pit and pump for a drainage system, calculate pit volume with pi D^2/4, and assess peak drainage from rainwater, floor cleaning, car washing, and fire loads.

Compute rainwater load from intensity, area, and surface coefficient to obtain 3.15 l/s. Size cylindrical sump pit with v = t q /4, 0.6 m depth, and 850 mm diameter.

Size a sump pump system for the sun pit, meeting a peak flow of 3.15 l/s with total head 8.68 ft, accounting for 3-inch piping and gate and check valves.

Design a sump pit for an ejector pump in a finished basement, accounting for water closets, urinals, wash basins, and kitchen sinks, using the established pump design.

Size the ejector pit by calculating peak drainage from fixtures, convert 38 fixture units to 24 gpm, and set a 0.6 m deep, 0.84 m diameter pit for basement.

Define the pipe invert as the inside bottom of the pipe, and define the invert level as the elevation from floor level to the pipe invert (denoted by I).

Learn to calculate the invert level of a straight pipe below ground using the distance from invert to ground, with a 0.2 example; the trick appears for a slow pipe.

Calculate slope from invert levels using the formula slope = (L1 - L2) / pipe length × 100; example yields 0.5% with L1 0.95, L2 0.2, length 150.

Learn the difference between manholes and inspection chambers and when entry is needed for inspection and maintenance. Ensure ventilation with vent pipes and note shapes square, rectangular, or circular.

Position manholes or inspection chambers where the sewer changes direction or invert level, at branch connections, and after every 30 m of straight external sewer.

Explore nine important design considerations for manholes, including depth from cover to outlet invert and a minimum 50 MB difference between inlet and outlet levels.

Inlet pipes must join the manhole at angles over 90 degrees to the flow, with cement mortar benching at least 150 mm wide and a 1:10 slope toward main channel.

Design manholes and inspection chambers with drop connections for invert differences above 600 mm. Install foot rests or rungs for depths beyond 600 mm and limit distance to building facade.

Identify manhole types by depth: shallow 0.7–0.9 m, normal up to 1.5 m, deep over 1.5 m—shallow uses light covers, normal heavy covers, deep heavy covers with built-in ladders.

Apply a five-step method to size manholes: determine inlet and outlet invert elevations, compute depths, select appropriate sizes, and assemble a manhole schedule.

Master the five-step method to size the external drainage manhole network: determine count, compute inlets and outlets, and select sizes using NBC tables.