First fix and second fix plumbing explained

Plumbers, builders and kitchen fitters talk about "first fix" and "second fix" as if everyone knows what they mean. They are just the two visits a plumber makes on most refits. The first puts the pipes where they need to be before the walls and floors are closed. The second, after plastering and tiling, connects the things you actually see and use. Most arguments on a refit come from something that should have been decided before first fix and was not.

First fix: the pipes you will not see

First fix happens with the room stripped. Walls may be open, floorboards up, studwork bare. The plumber runs or moves:

• hot and cold supply pipes to each tap, shower valve, toilet cistern and appliance;
• waste pipes from each fitting to the soil stack or the outside drain;
• any heating pipes for radiators or a towel rail;
• concealed parts, such as a built-in shower valve body or a frame for a wall-hung toilet.

Pipe ends are left capped at agreed heights. The choice of copper or plastic pipe, and where each is sensible, is covered in pipe types: copper and plastic. Pipes are fixed and supported so they will not knock or sag once covered. Routing pipes through timber floors is covered in pipe runs and notching joists. Some plumbers feed each room from a central plumbing manifold instead of branching tees.

Before the walls go back, a good plumber pressure-tests the new pipework and checks wastes for falls and leaks. Some concealed valves are designed to be tested at this stage. Ask how the test will be done and whether you can see it.

Second fix: the fittings

Second fix comes after plasterboard, plaster, tanking and tiling. The plumber returns to fit basins and taps, connect the toilet, fit the shower controls and head, hang radiators or towel rails, connect appliances, and seal around them. Then everything is filled, flushed, checked for leaks and shown to you working.

The same split applies to electrics and to joinery. An electrician first-fixes cables and back boxes, then second-fixes switches, lights and extractor fans. Any electrical work in a bathroom is for a qualified electrician. In England, Approved Document P explains when it has to be notified. We do not give wiring instructions.

Where this sits in a refit

The order is roughly: strip out, first-fix plumbing and electrics, boarding and plastering, tanking where needed, tiling, second fix, then sealing and decorating. Bathroom refit order goes through it stage by stage. A wet room or walk-in shower adds waterproofing between first and second fix: see wet rooms and tanking. In a kitchen, first fix puts the supply and waste where the sink and appliances will go before the units arrive. Kitchen sink installs covers the second-fix end.

If a gas boiler, gas pipe or gas hob is being moved or affected, that work is for a Gas Safe registered engineer and should be planned in at first fix too. See when to call a Gas Safe engineer.

What to agree before the walls close

Once tiles are on, moving a pipe means breaking them. Agree these before first fix, and confirm them on site before boarding:

• Exact positions. Tap heights, basin and toilet centre lines, shower valve height and head position. Have the actual products, or their fitting instructions, on site.
• Products chosen. A concealed shower valve, a wall-hung toilet or a wall-mounted tap needs its hidden parts set in at first fix. Changing your mind later can mean opening the wall. Bar vs concealed shower valves explains the difference for showers.
• Access. How you will reach isolation valves, a concealed cistern, a shower valve cartridge or a waste trap without breaking tiles.
• Wastes and falls. Where each waste runs, and whether a shower tray or floor former can drain properly from where it sits.
• Testing. That pipework will be tested before it is covered, and how.
• Photos. Ask for, or take, photos of pipe runs before boarding. They help the next person avoid drilling into a pipe.
• Paperwork. Who is responsible for any building regulations approval or notification, and for any notice to the water company. GOV.UK's building regulations approval page and its competent person schemes page explain the routes.

Pricing and timing

Quotes are sometimes split into first and second fix. Make sure each stage says what is included, who supplies the parts, and whether the plumber comes back for a final check after sealing. Gaps between the two visits are normal while other trades work. Hiring a plumber covers written quotes, insurance and what to ask.

What is the difference between first fix and second fix plumbing?

First fix is the pipework installed before walls and floors are closed: supplies, wastes and any concealed valve bodies. Second fix is after plastering and tiling: taps, toilets, basins, shower controls and appliances are connected and tested.

Should pipes be tested before plasterboard goes on?

Ask for it. Testing first-fix pipework before it is covered means a leak can be fixed without breaking new tiles. Agree how the test will be done.

Can I change my shower or toilet after first fix?

Sometimes, but a concealed valve or wall-hung frame is set in at first fix. Changing it later may mean opening the wall. Decide the products before the plumber starts.