Topic 3 Aboveground drainage Systems Click to progress
Topic 3 Above-ground drainage Systems Click to progress to next slide 1
Purpose of drainage systems • Whenever water comes into a home, it has to have a way to leave after it's been used. • This can be done through proper ventilated drain systems • To remove soil water • These will be from soil water fixtures (water-closets and urinals) • To remove waste water • These will be from waste water fixtures (basins; showers; sinks and bathtubs) Click to progress to next slide 2
Drainage system • A drainage system will (if installed properly): • Flush away all soil and waste water from fixtures; • Have no blockages • Trap and prevent foul or bad gases from entering the building • Allow foul air and gases to escape the system • Traps: • All fixtures need one, and only one, trap that is set at a level. Fixtures with an internal trap, like a toilet, do not need trap and should not have a separate trap. One trap provides the water seal to keep out sewer gas. Two or more traps impede flow and are more likely to become clogged. • However, one trap can service two fixtures (as in the case of double sink) Click to progress to next slide 3
Traps continued • At the bottom level of a fixture there is water • Water seal trap: • • Traps keep sewer gas out of the home Trap is that fitting installed underneath a fixture that holds little water Waste and soil fixtures are installed with separate traps Soil fixtures like WC come with a built-in trap, whereas; Waste water like sinks have a separate trap Gully has a trap at its lower level before it connects to the drain A bidet and urinal have a trap also; Click to progress to next slide 4
Drainage system continued • Trap venting: (Page 107) • • Vents protect the trap's water seal by admitting air into the drain and waste pipes • Trap venting is when we use water seal traps and ventilation pipes in the system Poorly ventilated drain will lead to water seal becoming broken (water at the bottom of a toilet drained out due to lack of air admittance into the drain) • Why venting? (Page 106) • Vents admit air into the pipes that helps equalize the air pressure in the pipes to prevent blowback and siphoning of the water seal in the trap. • • Venting allows water to pass out of the drains easily. Study Figure 3. 4 in page 108 to develop an idea how gases escapes drain system. Click to progress to next slide 5
When to use trap venting on soil fixtures: • There are specifics where and when to use a trap vent on soil fixture: • We install a trap vent where discharge from soil fixture has a vertical fall exceeding 1. 2 m (Figure 3. 6 and 3. 7 specifies where to install a trap vent). • Figure 3. 8 to 3. 10 shows how to ventilate your system • Trap vents can be omitted where: • No trap vent is required if the vertical fall is less or equal to 1. 2 m, or • Horizontal distance is greater or equal to 2. 4 m to ventilated drain. Click to progress to next slide 6
Waste fixtures: • Water seal need to be protected on waste water fixtures • Protect by installing a automatic vent valve (one-way or two-way where required) • Trap vent required on waste water fixtures where: • Trap vents required on all waste water fixtures on a one-pipe system • In a two-pipe system where if fall greater than 3 meters and distance greater that 3 meters • Trap venting can be omitted: • Where resealing trap is fitted to a waste fixture discharging into a gully; • Where the fall does not exceed 2 meters, and • The distance is less that 3 meters (Figure 3. 13; Click to progress to next slide 7
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