Erf Connection Design

Label

Description

LE

This is the length of an erf. You must decide whether this length is enough to drain the whole erf, and if necessary, adjust it upwards.

B

The distance the erf connection point on the erf is located from:

• The erf boundary for Outside Erf.

• The municipal sewer line for Inside Erf.

A

The distance a municipal sewer is located from the erf boundary. There is a negative result if the municipal sewer line position is Inside Erf.

MGL

The minimum or lowest ground level on an erf. There is an option on the Erf Connection Defaults that if selected, calculates the minimum ground level on the erf when the erf is indicated while the erf connection is added. If not, you must indicate the position for the minimum ground level point.

GLC

Ground Level at the erf connection.

MILS

The maximum or highest invert level of the sewer.
This is the highest invert level the municipal sewer can have at the plan position of the erf connection Y-piece, in relation to the MGL on an erf. This level is only required at the design stage, and allows you to place the sewer vertically for a row of erven. The actual invert level of the designed sewer at an erf connection Y-piece position must then be equal to, or lower than, the MILS.

Design Formulae:

Sewer inside erf:

MILS = MGL - DH - SLOPE x (LE - A) - Sewer DIA

Sewer outside erf or in road reserve:

MILS = MGL - DH - SLOPE x (LE + A) - Sewer DIA

ILS

Invert level of sewer.
These invert levels should be equal to, or lower than, the MILS.

ILC

Invert level of erf connection.
This is the highest level at which the erf connection can be, in order to be able to drain the erf in relation to MGL.

Design Formulae:

Sewer inside erf:

ILC = MGL - DH - SLOPE x (LE - A - B)

Sewer outside erf or in road reserve:

ILC = MGL - DH - SLOPE x (LE - B)

DS

Depth of sewer below MGL on erf.

Design Formulae:

DS = MGL - ILS

DC

Depth of Erf connection below GLC.

(DC = GLC - ILC)

DH

Depth of House connection below MGL on Erf.

(DH = Minimum Cover on house connection + Erf Connection DIA)

Label

Description

LE

This is the length of an erf. You must decide whether this length is enough to drain the whole erf, and if necessary adjust it upwards.

B

The distance the erf connection point on the erf is located from the erf boundary.

A

The distance a municipal sewer is located from the erf boundary.

MGL

The minimum or lowest ground level on an erf. There is an option on the Erf Connection Defaults that, if selected, calculates the minimum ground level on the erf when the erf is indicated while the erf connection is added. If not selected, you must indicate the position for the minimum ground level point.

GLC

Ground Level at the erf connection.

DC

Depth of Erf connection below GLC.

(DC = GLC - ILC)

DH

Depth of House connection below MGL on Erf.

(DH = Minimum Cover on house connection + Erf Connection DIA)

MILS

The maximum or highest invert level of the sewer.
This is the highest invert level the municipal sewer can have at the plan position of the erf connection Y-piece in relation to the MGL on an erf. This level is only required at the design stage, so you can place the sewer vertically for a row of erven. The actual invert level of the designed sewer at an erf connection Y-piece position must then be equal to, or lower than, the MILS.

Design Formulae:

Sewer inside erf:

MILS = MGL - DH - SLOPE x (LE - A) - Sewer DIA

Sewer outside erf or in road reserve:

MILS = MGL - DH - SLOPE x (LE + A) - Sewer DIA

ILS

Invert level of sewer.
These invert levels should be equal to, or lower than, the MILS.

ILC

Invert level of erf connection.
This is the highest level at which the erf connection can be in order to be able to drain the erf in relation to MGL.

Design Formulae:

Sewer inside erf:

ILC = MGL - DH - SLOPE x (LE - A - B)

Sewer outside erf or in road reserve:

ILC = MGL - DH - SLOPE x (LE - B)

E

The height difference between Invert Level of Sewer (ILS) at the y-piece and the Invert Level of the erf connection (ILC) at the end of the connection.

Design Formulae:

Sewer inside erf:

E = ILC - ILS

Sewer outside erf or in road reserve:

E = ILC - ILS