Water-supply and drain work sets the final service points for kitchens, bathrooms, and laundry areas, then replaces or extends the pipes that feed and empty them. Most of the installation disappears behind walls and floors, so the route, joints, drainage falls, and test records need to be checked before the finishes close over it.
When this work is needed
Pipework usually changes when a kitchen or bathroom moves, or when a dishwasher, washing machine, concealed tap, or new drain point is added. If fixtures stay where they are, inspect the age, leak history, and condition of the existing branches before deciding on wholesale replacement.
Decide before opening the floor
Fix the final fixture positions and agree which pipes will stay, move, or be replaced.
Final positions of taps, drains, toilet, sink, and water-using appliances
Existing sections to retain and the exact removal, replacement, and extension boundaries
Pipe materials and sizes, plus insulation against heat loss, condensation, or freezing
A drain route with workable falls and the wall or floor excavation it requires
Who witnesses pressure and flow tests and receives the photographs before covering
Check in the quote
A single line for plumbing is not enough. Look for the route, materials, testing, and handover separately.
Are removal, wall and floor cutting, and waste disposal included?
Are supply and drain points, pipe lengths, materials, and sizes listed by room?
Does the scope include hot-water insulation, cold-pipe condensation control, and freeze protection where needed?
Are pressure and flow tests, repairs, and retesting included?
Will you receive dimensions and photographs of the concealed routes with the test results?
What to check on site
Once the pipework is buried, its joints and falls can no longer be seen. Record each handoff from the retained ends to the final fixture locations before anything is covered.
01Remove old pipes
As old pipework is removed, mark the supply and drain sections that will remain and cap every open end. If corrosion or cracking reaches the proposed connection point, reassess the replacement boundary rather than attaching a short new piece to weak pipe.
02Install water-supply piping
Run hot and cold supply lines separately to each fixture and secure them so they cannot move. Keep valves and joints accessible where possible, and use uninterrupted insulation through areas exposed to condensation or freezing.
03Extend kitchen and laundry piping
Set kitchen and laundry connections from the cabinet and appliance drawings. Check them against the actual product dimensions so hoses do not kink behind drawers or machines and valves and traps remain reachable.
04Install bathroom piping
Set basin, shower, toilet, and channel-drain centres from the finished tile faces. Confirm that tap elbows are rigid and that drain heights allow the waterproofing and tiled falls to be formed by the following trades.
05Finish drain piping
Run water through every drain to confirm a continuous fall without ponding, then pressure-test the supply joints. Check traps and ventilation against odour, and photograph the complete routes and results before covering.
Where problems usually start
Concealed supply jointAn incompletely pressed fitting can leak only after the pipe has been buried, so every joint must be inspected during the pressure test.
Poor drain fallA flat or sagging section holds water and waste, leading to repeated blockage, backflow, and odour.
Broken hot-water insulationGaps around fittings increase the wait for hot water and can allow condensation to wet nearby finishes.
A falling gauge does not automatically mean every pipe must be replaced. Check the gauge and temporary caps first, then isolate sections to locate the failed joint.
Before covering, keep the pressure record, drain-flow video, branch locations, and dimensions from fixed wall and floor references. They will guide later drilling and maintenance.
Timing and records
Allow about 16 to 24 hours on site. Pipe extent, excavation, test waiting time, and repairs after a failed test can change the programme, so separate installation from test holds.
Keep pipe materials and sizes, fittings, branch locations, insulation, starting and finishing pressure, drain-flow results, and full-route photographs taken before concealment.
If you have a quote or photographs before covering, I can help check the pipework boundary, drain falls, and test evidence.
