Waste Pipe Sizing and Types

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Questions and Answers

What type of fittings should be used for horizontal to horizontal changes in waste piping?

T fittings

45 ° fittings

Short radius fittings

Long sweep fittings (correct)

What is the ideal slope for horizontal waste pipes to ensure proper drainage?

2% (correct)

Which fitting is most appropriate for a vertical to horizontal direction change in waste piping?

T fitting

Y fitting (correct)

Elbow fitting

Short radius fitting

Why should the cleanout be sized equal to the diameter of the waste pipe?

To avoid interference during cleaning Signup and view all the answers

What potential issue arises from using a T fitting on horizontal installations?

Tilted or crooked joint connections Signup and view all the answers

What is the purpose of cleanouts in a waste pipe system?

To allow for easy access during maintenance Signup and view all the answers

Which of the following is a consequence of improper sizing of waste pipes?

Possible trap seal loss Signup and view all the answers

Which type of venting has been shown to be safe in certain installations according to recent studies?

Wet venting and stack venting Signup and view all the answers

Which type of waste pipe directly connects to the plumbing system?

Direct Waste Signup and view all the answers

What is the recommended minimum size for a kitchen sink waste pipe?

38 mm or 1 ½ inches Signup and view all the answers

Which of the following fixtures is served by a minimum 50 mm waste pipe?

Shower Bath Signup and view all the answers

What does the 'scouring action' in pipes refer to?

The effect of wastewater moving through the pipe Signup and view all the answers

What is a common cause of trap seal loss in waste pipes?

Evaporation due to prolonged inactivity Signup and view all the answers

Which type of fixtures typically require indirect waste connections?

Soda fountains Signup and view all the answers

What is the recommended pipe size for a urinal waste pipe?

50 mm Signup and view all the answers

When sizing a waste pipe, what is considered one fixture unit?

1 cubic foot of waste discharged Signup and view all the answers

What is the recommended method for joining cast iron pipes?

Using oakum and lead at hub and spigot connections Signup and view all the answers

What causes the solid waste to remain at the bottom of the drainage pipe?

Shallow water flow and improper pipe size Signup and view all the answers

What is the ideal water flow depth to maintain effective drainage in a pipe?

Equal to the pipe radius Signup and view all the answers

Why is it important to follow manufacturer specifications when joining pipes?

To ensure effective joints and prevent failures Signup and view all the answers

Which factor determines the size of the waste pipe according to plumbing codes?

Fixture Unit Value as waste load Signup and view all the answers

What is a common consequence of using a too small drainage pipe?

Creation of back-pressure and flooding Signup and view all the answers

When are plastic pipes typically supported when installed vertically?

Every 1m Signup and view all the answers

What is the primary purpose of conducting tests on plumbing fixtures according to the Uniform Plumbing Code Committee?

To determine the flow rates of water discharged from fixtures Signup and view all the answers

Study Notes

Waste Pipe Sizing

The amount of water discharged by a fixture in one minute is called a Fixture Unit (FU)
One FU is equal to one cubic foot or 30 liters of water.
The National Plumbing Code uses Fixture Unit Value (DFU) to determine the size of waste pipes.
Waste pipes are classified into two types: Direct and Indirect.
A Direct Waste Pipe is connected directly to the plumbing system.
An Indirect Waste Pipe is not directly connected to the plumbing system and serves fixtures like soda fountains, bar waste, refrigerators, drinking fountains, and air conditioning units.

Recommended Waste Pipe Sizes

Sink waste pipes should be at least 38 mm (1 ½”) in diameter, with 50 mm (2”) being more common.
Floor or wall-mounted slop sink traps should be 75 mm or 100 mm, while wall-mounted traps should be 50 mm.
Bathtubs, laundry tubs, and lavatories require 38 mm to 50 mm diameter waste pipes.
Shower baths and urinals require a 50 mm diameter waste pipe.

Waste Pipe Installation

Horizontal waste pipes should be installed at a 2% slope, meaning a 2 cm incline per meter of pipe length.
The correct size waste pipe is essential for efficient flow and prevents backpressure, siphoning, and floor flooding.
Proper pipe size and slope ensure a 50% depth of flowing water, which helps prevent clogging.
Fittings should be used according to manufacturer specifications to ensure effective pipe joints.
Cleanouts, strategically located access points, should be provided for cleaning and maintenance in case of blockages.
Cleanouts should be sized equal to the diameter of the waste pipe they connect to.

Common Residential Drainage Fixtures and Fixture Units

Bathtubs and showers have a DFU of 2.
Urinals have a DFU of 3.
Floor Drains, Laundry Tubs, and Kitchen Sinks have a DFU of 2.
Water Closets have a DFU of 4.
Lavatories have a DFU of 1.

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Description

Test your knowledge on waste pipe sizing and classification based on the National Plumbing Code. This quiz covers fixture units, direct and indirect waste pipes, and recommended sizes for various plumbing fixtures. Prepare to explore the essential guidelines that ensure effective plumbing design.