Fixture counts and measured pipe runs turned into pipes, fittings and valves.
Electrical and plumbing. 5 questions answered below, each with the arithmetic behind it and the limits of what the tool decides. Open the Plumbing Estimator tool.
A plumbing estimate follows the pipe. Runs are measured, fittings are counted where the runs turn and branch, and fixtures are counted where they are installed. The three are bought differently, so they are calculated separately and then presented as one order. What the estimator refuses to do is guess the route. A plumbing layout in a building that is not yet built is a drawing rather than a measurement, and a measured route and a straight line between two fixtures differ by a surprising amount once risers, bends and falls are counted. Where a run has not been measured, the page reports it, which is the difference between an estimate that can be checked and one that merely looks complete.
A bathroom refit with four fixtures, a measured supply run of twenty two metres in fifteen millimetre pipe and a waste run of nine metres in forty millimetre, gives thirty one metres of pipe, twenty eight fittings at the terminations and branches, and the fixtures with their valves and traps. Add a water heater and its isolation valves and the schedule grows by the fittings that connection needs. Nothing in the order came from the fixture count alone, which is the reason the runs are the input that matters.
Measure the runs and count the fixtures. Supply, waste and drainage are measured separately because they take different pipe and different falls, and fittings are counted where those runs turn or branch. The estimate then returns pipe by diameter, fittings by type and the fixtures with their valves and traps. A plumbing estimate that starts from a fixture count and a rate per bathroom will be short on pipe and fittings every time.
No, it does not. A septic tank, soakaway or treatment plant is a separate design, sized from the occupancy and the ground, and it has its own material and excavation quantities. The estimator covers the pipe, fittings and fixtures inside the building. Where a drainage run leaves the building, measure it as a drainage run and price the tank or soakaway separately, so the two numbers stay checkable.
From the design and the fixture demand, not from a table in a quantity tool. Supply sizes follow the flow and pressure available, waste sizes follow the fixtures discharging into them and the fall, and drainage follows both plus the local regulations. The estimator asks which size you are running and adds the length by size, so the order matches a design that has already been made.
Pipe measured by length, fittings counted, and the fixtures you schedule with the valves, traps and connections each one needs. Supply, waste and drainage stay on their own lines. Insulation, supports and fixings are counted where you specify them. It is a material estimate for the plumbing installation, and it deliberately stops at the fixtures rather than wandering into the rooms around them.
Falls add length on drainage runs, since a pipe running at a gradient covers more distance than its horizontal projection, and bends add fittings at every change of direction. Measure the route along its actual line and count the bends the route needs. The estimator uses your measured route, and a route you have not measured is reported as missing instead of being closed with an assumption.