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SmartScreenLevel 2 NVQ Diploma in Plumbing and Domestic Heating

Unit 010 Handout 2

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Unit 010: Sanitation systemsHandout 2: Other methods of connecting to the drainage system

There are a number of additional methods of connecting ground floor appliances to

the drainage system. The requirements for trap seal depths and pipe sizes coveredearlier still apply equally to these types of installation.

The stub stack system

A stub stack is a short unventilated discharge stack. In order for this type of stack tobe used the following conditions apply:

Where one or more stub stacks are used in a property then the head of the drainmust be ventilated by means of a stack vent.

The distance between the finished floor level (FFL) and the drain invert level mustnot exceed 1.3m and the highest appliance connection must be within 2.0m of thedrain invert level.

The stub stack system

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SmartScreenLevel 2 NVQ Diploma in Plumbing and Domestic Heating

Unit 010 Handout 2

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www.SmartScreen.co.uk

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Direct WC connection to drain

An unventilated WC connection may be made directly to the drainage system providedthat the invert of the drain is within 1.3m of the finished floor level (FFL) on which theWC is located.

Stub waste connection

The stub waste connection which includes making a direct waste pipe connection to thedrainage system via an unventilated sealed connection for ground floor appliances isoften used to make remote waste connections such as kitchen sinks and washingmachines/dishwashers. The main requirement when connecting via a stub waste is toensure that a deep seal trap is installed on the appliance.

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SmartScreenLevel 2 NVQ Diploma in Plumbing and Domestic Heating

Unit 010 Handout 2

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Direct waste connection to gully

Kitchen sink/washing machines are often connected to the drainage system via a gully.Key features of this type of installation are:

a gully that is capable of accepting waste pipe connections must be installed. A backinlet type gully (BIG) is often used for this purpose

the waste pipe must discharge below any grid fitted to the gully but must alsoterminate above the water level in the gully

certain ground floor appliances connected to a gully may be of the shallow seal typetrap with a 38mm seal depth this is because there is an air break between the gullycontents and the pipe end.

Test

1. What is the distance of the highest branch connection that can be made on astub stack from the invert level of the drain?

2. What is the name of a waste connection made directly to a drainage system?

3. How could the 1.3m distance between the floor level and drain invert level beexceeded when making a direct WC connection to the drainage system?

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SmartScreenLevel 2 NVQ Diploma in Plumbing and Domestic Heating

Unit 010 Handout 2

2012 City and Guilds of London Institute. All rights reserved.

www.SmartScreen.co.uk

Page 4 of 4

Points to remember

Check the system it is important to check the type of system you will be

connecting into to help prevent making a connection to the wrong type of sewer.

Discharge stack also known as a soil stack this is the main above groundsanitation pipe.

Ventilating pipe this is the pipe that allows air into the system to relieve pressureproblems. The air helps create an equilibrium in the system

Invert of the drain this is the bottom of the drainage pipe at the base of the stack.

Radius of bend imagine that the bend was part of a circle; this is the circlesradius.

Wet portion of the stack the part of the stack that has waste water running

through it.

Dry portion of the stack the part of the soil stack that is above the wet portion that

will never normally have waste water running through it.

Expansion in pipework consideration for this must be included in the installation

of pipework to prevent problems.

Co-efficient of expansion of PVCu is approximately 0.06mm/m/C.

Expansion gaps and joints need to be provided in order to cope with thermalexpansion in systems.

Self-cleansing velocity the speed of the flowing water required to prevent a build

up of deposits in pipework. This is achieved by installing the pipe with the proper

gradient.

Cross flow zones must be followed for the system to work correctly.

Maximum pipe lengths and gradients must be adhered to otherwise another

method of ventilation should be used.