On a residential development, the most useful sign-offs for a plumbing, heating and gas package come at two points on every plot: before first-fix pipework is hidden by plasterboard, floor decks or screed, and before the plot is offered for completion. At first fix, you want evidence that water, heating and gas pipework was tested and inspected while still accessible. At second fix, you want the commissioning records and notifications that building control and purchasers expect. Agree what each sign-off contains before work starts, and record it plot by plot.
This article assumes the package has been let. For the tender pack itself, see our guide to new-build plumbing tenders.
Why plot-by-plot sign-off matters
Dryliners, floor layers and kitchen fitters close up pipework quickly. A leak or untested gas run found after decoration means opening up finished work, and a missing certificate can hold up a completion. A short hold point on each plot, released by a named person, helps reduce these risks.
First fix: test before it is concealed
Water and heating pipework
In England and Wales, the Water Supply (Water Fittings) Regulations 1999 require a water system to withstand at least one and a half times its maximum design operating pressure. Schedule 2 sets out deemed-to-satisfy test procedures, with separate ones for systems that include plastic pipe. The regulations also require every water system to be tested, flushed and, where necessary, disinfected before it is first used.
In practice, test the section about to be covered and record the plot, section, procedure, pressure, duration, result and tester. Heating pipework under floors or behind boards also needs testing before it is covered; agree the method with the designer, following the pipe manufacturer's instructions.
Pipe routes, joints and access
The same regulations say no water fitting may be embedded in a wall or solid floor, and fittings designed to be operated or maintained, and joints, must not be concealed. "Concealed" includes fittings in a chase or duct, below ground, or anywhere that is inaccessible or difficult to reach. Before boarding or screeding, check that routes follow the agreed design, ducting or sleeving is in place, and valves and joints stay accessible.
Gas installation pipework
Under the Gas Safety (Installation and Use) Regulations 1998, anyone whose work on installation pipework might affect its gastightness must immediately ensure it is tested for gastightness and examined to verify it has been installed in accordance with the regulations. Regulation 19 limits where pipework may run: pipework in a solid wall or floor must be protected against failure caused by movement, and pipework should generally not run in a wall cavity except to pass through it.
On new-build plots the gas supply is often not live at first fix. Regulation 22 says gas must not be allowed into the pipework until it has been purged and tested. Agree who carries out the final test and purge when the meter is fitted, and how it is recorded.
Second fix: commissioning and records
At second fix, sanitaryware, heat source, cylinder, emitters and controls are connected, and the systems are filled, flushed and commissioned. Agree three points in advance.
Flushing and commissioning. Approved Document L, Volume 1 (2021 edition, incorporating 2023 amendments) says heating and primary hot water circuits should be cleaned and flushed before a new heating appliance is installed, with a suitable inhibitor added, and domestic central heating prepared and commissioned to BS 7593. The Benchmark Commissioning Checklist can be used to show commissioning was done.
The commissioning notice. Regulation 44 of the Building Regulations 2010 requires the person carrying out the work to notify building control that fixed building services have been commissioned. For new dwellings, Approved Document L says a commissioning plan should go to the building control body with the design-stage energy calculations, and that building control may withhold a completion certificate until it receives the notice. Decide who prepares the plan and who sends the notice.
Gas appliance notification. Agree which installations need building-regulations notification, who will submit it and which compliance documents will go into the plot handover file. Ask the Gas Safe registered business to confirm the applicable requirements and submission deadline for the project.
Approved Document L has different editions and transitional arrangements. Ask the designer and building control body to confirm which requirements apply to each plot; the guidance discussed here is for England.
Checking gas registration
Under regulation 3 of the gas regulations, a business carrying out gas work must belong to a class of persons approved by HSE, which at present means Gas Safe Register. Regulation 4 adds that anyone who controls gas work at a place of work must take reasonable steps to make sure the person doing it is registered. Check that registration is current and the categories of work cover the scope. MCN Mechanical & Electrical lists its accreditations and memberships, and you can ask for current supporting documentation for your tender.
Reference: The Water Supply (Water Fittings) Regulations 1999, Schedule 2 (paras 7, 12 and 13) · The Gas Safety (Installation and Use) Regulations 1998, regulation 3 (qualification and supervision) · GSIUR 1998, regulation 4 (duty on employer) · GSIUR 1998, regulation 19 (enclosed pipes) · GSIUR 1998, regulation 22 (testing and purging of pipes) · HSE: Gas Safe Register · HSE L56, Safety in the installation and use of gas systems and appliances (ACOP) · The Building Regulations 2010, regulation 44 (commissioning) · Approved Document L, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments (Section 8, paras 8.2–8.8) · GOV.UK: Conservation of fuel and power, Approved Document L (lists the 2026 edition) · Gas Safe Register: Notification factsheet for consumers
A simple plot sign-off record
A one-page record for each plot usually covers:
Plot number, house type and drawing revision installed.
First-fix water and heating tests, with name and date.
Gas pipework test and examination, and whether the supply is live.
Pipe route and access check before boarding or screed.
Second-fix flushing, inhibitor, commissioning checklist, and final gas test and purge.
Commissioning notice and Gas Safe notification references.
Outstanding items, each with an owner and date.
Agree the sign-offs before work starts
Agree these records at tender or pre-start, when they can be priced and programmed. For a wider view of acceptance and handover, see our article on M&E commissioning and handover.
Planning a plumbing, heating and gas package for a residential development? Send MCN Mechanical & Electrical your plot schedule, house types, programme and the sign-off records you need at each stage. Read about our new-build plumbing, heating and gas packages or discuss your package with our team.