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Plumbing formula examples: downpipes, sewer pipes and bends

Dive into example plumbing formula.

Updated this week

Before reading this article, ensure you have read Adding parts & labour to measurements and Using formula within Groundplan articles to aid in understanding the following formula examples.

📝The formula values provided in this article are for example purposes only.

Term

Explained

count

total counts

len

total metres measured

count or len / x

total count/length divided by an amount

count or len * x

total count/length multiplied by an amount

ceil(x)

rounding up a decimal value to the next whole number

Downpipe

Example parts for a downpipe count measurement:

Part

Explanation

Formula

UoM

100mm DVW pipe (6m)

How many 6m lengths are required to complete downpipes when 3 metres 1/2 length (3m) is needed for each downpipe

count*0.5

lengths

100mm PVC 90° bend

How many 90° bends are required when 3 are needed for each downpipe

count*3

each

100mm saddle clip

How many saddle clips are required when 3 are needed for each downpipe

count*3

each

100mm classic expansion outlet

How many expansion outles are required for each downpipe

count

each

Downpipe nozzle

How many nozzles are required for each downpipe

count

each

(optional) 100mm junction (for 80%)

How many junctions are required for 80% of the downpipes needed

ceil(count*0.80)

each

100mm DWV Sewer (av. 1.5m depth)

Example parts for a 100mm DWV average 1.5m depth length measurement:

⚠️Warning: This example does NOT use the depth / width component in the measurement unit section:

Part

Explanation

Formula

UoM

100mm DWV

How many 6m lengths required for the total length measured

ceil(len/6)

lengths

Trench work (1.5m average depth)

How many m3 for the total length measured multiplied by the 600mm wide by 1.5m deep

len*0.6*1.5

m3

Crushed rock (400mm average depth)

How many m3 for the total length measured multiplied by the 600mm wide by 400mm deep

len*0.6*0.4

m3

Sewer Bend

Example parts for a sewer bend count measurement:

Part

Explanation

Formula

UoM

100mm 45° bend

Require 2x 45° bends for each 90° count

count*2

each

100mm DWV

Allowing an additional 600mm of 100mm DWV for each upwards pipe (Grouping with Sewer Measurement) divided by 6m lengths required for the total length measured

ceil(len*0.6/6)

lengths

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