Ask for a plumbing price on a house and you will usually get one number. Ask what is in it and the number starts to move. Pipes, fittings, insulation, soil and waste, sanitaryware, taps, traps, testing, making good: each one is a separate order and a separate trade argument.
The reason this matters is that plumbing is one of the few trades where the material is cheap and the access is expensive. A push fit elbow costs a fraction of the cost of opening the floor again to reach it. So the takeoff has to do two things at once: get the quantities right, and make sure the specification is complete enough that nobody is surprised later.
This guide covers first fix and second fix separately, because they are measured differently and ordered at different times.
First fix: outlets, runs and the pipe between them
First fix is everything that goes inside the walls and floors: supply pipe, soil and waste, and the connections that will later meet taps and sanitaryware.
Count the outlets first. On a typical three bedroom house that is:
Cold water: kitchen tap, washing machine, dishwasher, outside tap, two basins, bath, two WCs, shower
Hot water: kitchen tap, two basins, bath, shower
Soil: two WC connections plus the stack
Waste: basins, bath, shower, kitchen sink, appliances, plus the stack connections
That is around 20 supply outlets and 12 waste connections. Each one needs a pipe run to it, and each run is measured, not guessed.
Measuring supply runs
Work pipe by size, because sizes are priced differently and cannot be substituted:
Pipe size
Serves
|---|---|
15 mm
Individual outlets: basins, WCs, washing machine
22 mm
Groups: a bathroom, kitchen, or a short main
28 mm
Main from the incoming supply, long runs
Measure the route as built, meaning along walls and up floors, not the straight line between two points. Then add the rises: an outlet at 1.0 m above floor on a first floor room has a rise from the ceiling void or the floor void, and that rise is real pipe.
A working rule for domestic work is 8 to 12 m of pipe per outlet when the runs are long and the plan is spread out, and 5 to 8 m when the bathroom is above the kitchen and the runs are stacked. A house with 20 outlets therefore uses somewhere between 120 and 220 m of pipe, and that spread is why two plumbers give different prices for the same plan.
Fittings, and why elbows are expensive
Every elbow, tee and coupler consumes pipe and adds a joint. On a typical first fix you can expect 1.5 to 2.5 fittings per metre of pipe in a house with normal routing, and more where the layout is awkward.
The practical consequence: routing matters more than material choice. A run that takes three extra elbows to save half a metre of pipe costs more in fittings and time than it saves. That is a design decision with a price tag, and a good takeoff records the fitting count so the decision is visible.
Allow 5 percent spare on fittings, more if the pipe is push fit and the installers are cutting on site.
Soil and waste
Soil pipe takes the WC connection to the drain. It is measured in metres, in the diameter the code allows (often 110 mm), plus a stack, a branch for each WC, and an air admittance valve or a vent pipe to roof.
Waste pipe carries everything else: basins at 32 or 40 mm, baths and showers at 40 or 50 mm, kitchen sinks at 50 mm. Measure each branch and each shared run, and do not forget the falls. Waste needs 18 to 90 mm per metre depending on diameter, and the fall has an effect on the total length because the run slopes.
Also count the traps. Every outlet needs one, and a trap is a fitting with a price, not a detail.
Insulation, sleeves and clips
These are small items that make up a real percentage of the material cost:
Pipe insulation on all hot runs and on cold runs where condensation is a risk
Sleeves where pipe passes through masonry or a party wall
Clips at spacing the code requires, typically 300 mm for plastic and more for copper
Fire collars where pipe passes a compartment wall or floor
Isolating valves on every outlet group, which is a fitting most first estimates omit
Fire collars and isolation valves are the two that catch people out. Both are required in most jurisdictions, both are cheap individually, and both are missing from a rate quoted per outlet.
Second fix: the visible half
Second fix is where the money goes on the material side, because sanitaryware and brassware are the expensive items and the client has opinions about them.
WCs, with seats and cisterns or flush plates
Basins, pedestals or vanity units
Baths, including the panel and the tap holes
Shower valves, heads, risers and trays
Kitchen sink and tap
Wastes and traps
Flexible connectors and sealing
The takeoff rule here is simple and often ignored: price what has been specified, and list the specification in the bill. A bathroom suite range can differ by a factor of five, so a per bathroom allowance is not a quantity, it is a placeholder.
Second fix also needs the showers, pumps and any water treatment counted as units with an electrical connection, because a pump needs a supply and that supply is an electrician's cost, not the plumber's.
A worked example, one bathroom
A family bathroom, first floor, above the kitchen, replacing an existing room:
Supply: basin cold, basin hot, WC cold, bath cold, bath hot, shower cold, shower hot. Seven outlets at an average 9 m of pipe each = 63 m, split roughly 45 m of 15 mm and 18 m of 22 mm
Waste: basin 40 mm at 4 m, bath 40 mm at 3 m, shower 40 mm at 3.5 m, plus 6 m of shared 50 mm to the stack = 16.5 m
Soil: 2 m of 110 mm plus one branch
Fittings: about 40 elbows, tees and couplers, plus 7 isolation valves, plus 12 clips
Insulation: 25 m on hot runs
Sanitaryware: one WC, one basin and pedestal, one bath, one shower valve and head, one shower tray
Traps and wastes: four
Testing: one pressure test on the supply, one waste flow test
That is a modest room and it is roughly 60 separate line items once the fittings are broken out. Any estimate that reduces it to a single figure is an allowance, and allowances are how bathroom budgets fail.
Push fit, solvent weld and copper
The material choice changes both the quantity and the labour, and the takeoff should say which system is being used.
Push fit is fast and forgiving, and the fittings cost several times what a solvent or compression fitting costs. On a house with 100 fittings that difference is significant, and it is usually justified by the time saved.
Solvent weld is cheap in material and slower, and it cannot be adjusted once set, so the setting out has to be right first time.
Copper is durable, expensive, and needs a heat source and a hot work permit in many buildings. Its fittings are priced by weight and rise with the metal market, which is a live risk on a long project.
None of these is universally better. The point for an estimator is that the same layout has three different material prices and three different labour outputs, so a rate per outlet without a system name is not comparable.
Pressure testing and commissioning
A supply system is tested before it is covered: fill, pressurise, hold, inspect. A waste system is flow tested. Both take time and both need to be witnessed if the project has any inspection regime.
Add to this the commissioning items that are easy to skip: flushing, water treatment if specified, balancing, and the certificates. On a domestic job this is a few hours. On a commercial job it is a day or more, and it belongs in the programme rather than in the last week.
Productivity and what changes it
A competent plumber first fixes 6 to 12 outlets a day on domestic work, depending on how much chasing and drilling is needed and whether the pipe is being run in a stud wall or a solid one.
Second fix is faster per item but involves waiting: for tiling, for the electrician, for the client to choose a tap. A second fix that is priced as continuous work is a second fix that will be done in three visits.
The realistic allowance for a bathroom is two to three days of first fix including the soil connection, and one to two days of second fix, with a return visit for commissioning.
Ordering against the programme
Plumbing material is ordered in two waves and the split matters. First fix material is bought against the structure being ready. Second fix material is bought against the client having chosen, which is a different date and often a later one.
The failure that costs money is buying second fix items early to get a discount, then discovering the client has changed the shower valve and the tray no longer fits the room. Sanitaryware sits in a garage for three months and then goes back.
Order first fix when the walls are up. Order second fix when the selection is confirmed in writing, and record the date. That single discipline removes the most common cause of a stalled bathroom.
Working around existing services
Renovation plumbing is priced on time, not on quantity, because the quantity is unknown until a floor comes up.
Three things change the arithmetic. Existing pipe may be in a material that cannot be joined to the new system without an adaptor, which means a fitting nobody ordered. Existing pipe may be at a size that no longer complies, which means replacing more than planned. And existing isolation may not exist at all, which means draining the whole house to change one valve.
The estimate for renovation work should carry a discovery allowance, stated openly, rather than a lower fixed price that will be renegotiated the moment the floor opens. Clients accept a stated allowance. They resent a variation.
Condensation and the pipe you cannot see
Cold water pipe in a warm, humid building sweats. A cold main running through a kitchen ceiling will drip onto the plasterboard below and the stain will appear months later, far from the pipe.
Insulating every cold run in a heated space is cheap at first fix and expensive to add later. The same applies to the cistern and to any tank in a warm roof space. It is a small line in the takeoff that prevents a call back.
Frequently asked questions
How much pipe does a house need? Between 120 and 220 m of supply pipe for a three bedroom house, depending on how spread out the outlets are.
How many fittings per metre of pipe? 1.5 to 2.5 on typical domestic routing, more on awkward layouts.
Do I need isolation valves on every outlet? Not every outlet, but every group, and every item that will need servicing. It is the cheapest insurance in the trade.
What fall does a waste pipe need? 18 to 90 mm per metre depending on diameter, with 40 mm pipe typically at 18 to 25 mm per metre.
Why are plumbing quotes so different for the same bathroom? Different pipe systems, different fitting counts, different sanitaryware specifications, and one of them is probably excluding making good.
Is push fit acceptable? In most domestic situations it is, where it is accessible and installed to the manufacturer's instructions. It is a specification choice, not a shortcut.
Estimate it in FRELUX
The FRELUX plumbing calculator splits first fix and second fix, counts outlets and runs by pipe size, and prices fittings, insulation and sanitaryware from your local price book so the allowances become quantities.