Plumbing Trade Math: Pipe Offsets, Slope, Flow & Fixture Units

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Turn six cut lengths from a Brightwater Plumbing drawing into decimal inches and millimetres, total the pipe and convert metric fixture dimensions to the nearest 1/16 inch.
• Find the travel for five simple offsets with different fittings, then use Pythagoras to solve four rolling offsets and their cut lengths.
• Calculate the fall, percent grade and end depth of five drain runs, then work backwards to the longest island-sink branch that still reaches the stack.
• Calculate how much water six pipe runs hold, in US gallons and litres, and how much that water weighs when the runs are full.
• Calculate the cross-section area and water velocity in five supply pipes, flag the ones above the velocity limit and find the largest flow each size can carry.
• Total the drainage fixture units of a fictional bathroom branch, look up the smallest pipe size in an illustrative table and apply a second rule for toilets.
• Add up a fictional family's busiest hour of hot water, estimate the recovery rate and first-hour rating of four tank heaters and pick the smallest one that covers the peak.
• Turn the material list of a fictional bathroom job into order quantities and line costs, build the quote from materials, markup and labour, and chart where the material money goes.