UFH Manifold Installation & Pressure Testing: Method Statement Requirements and Risk Controls

Table of Contents

• Introduction: Why Manifold Installation and Pressure Testing Need Detailed Method Statements
• Manifold Installation Method Statement
• Hydraulic Pressure Testing Method Statement
• Why Air Pressure Testing is Prohibited
• Screed Contractor Interface Controls
• What Your Method Statement Must Cover
• Frequently Asked Questions

Introduction: Why Manifold Installation and Pressure Testing Need Detailed Method Statements

Two phases of wet UFH installation carry specific method statement requirements that go beyond general plumbing RAMS: manifold installation (because of the coordination with controls and electrical wiring) and pressure testing (because of the risk of injury from incorrect procedure and the no-air-testing requirement).

Principal contractors on residential development and commercial projects increasingly require these phases to be described in detail in the submitted RAMS. This guide provides the method statement content for each phase and explains the rationale for the safety controls required. Full trade RAMS guidance is available in our underfloor heating RAMS resource.

Browse all trade RAMS templates on the RAMS AI trade hub — covering 22 specialist construction trades.

Manifold Installation Method Statement

The method statement for manifold installation must describe the following sequence:

1. Survey and mark manifold positions — Confirm manifold positions with the principal contractor and structural engineer (where manifolds will be fixed to blockwork or lightweight partition walls, load-bearing capacity must be confirmed). Mark positions on drawings.
2. Fix manifold brackets — Install manifold brackets at the specified height. Use appropriate fixings for the substrate: stainless steel screws and raw plugs for masonry, toggle bolts or timber noggins for lightweight partitions.
3. Install manifold assembly — Mount the manifold on brackets and confirm it is level. Connect supply and return tails using appropriate fittings — compression or press-fit for copper connections, push-fit for plastic pipework. Torque compression fittings to the manufacturer's specification.
4. Install flow meters and commissioning valves — Set flow meters to the design flow rate for each zone before pipe connections are made (this is easier before the loop pipes are connected).
5. Connect UFH loops — Connect each UFH loop pipe to the manifold port in order. Label each loop connection to match the circuit plan drawing. Use the manufacturer's approved fittings.
6. Install actuators — Mount zone actuators on the manifold valves. Confirm that actuator type is compatible with the manifold (normally open vs. normally closed). Wire actuators to the thermostat wiring centre — this step must be carried out by a qualified electrician.

Hydraulic Pressure Testing Method Statement

The pressure test must be conducted before screed is laid and before any insulation or floor covering conceals the pipework. The test procedure:

1. Pre-test checks
   • All loop connections made to manifold
   • All manifold end caps in place
   • All automatic air vents closed
   • Manual air vent on manifold open to allow air purging during fill
   • Calibrated pressure gauge connected to test point — confirm gauge calibration certificate is current
2. Fill and purge
   • Open each loop valve in turn and fill the loop from the return side, pushing air out through the flow manifold manual vent
   • Continue until water runs clear from each loop with no air bubbles
   • Close manual vent after purging is complete
3. Pressurise to test pressure
   • Using a hand pump or pressure testing kit, pressurise the system to 6 bar (or the manufacturer's specified test pressure if lower)
   • Check all connections for immediate leaks — rectify before proceeding
4. Hold test
   • Hold at test pressure for 1 hour — record pressure at 15-minute intervals
   • Maximum permissible pressure drop: typically 0.6 bar in the first hour (accounts for pipe expansion)
   • If pressure drop exceeds this, stop the test, identify and repair the leak, and retest
5. Extended test at working pressure
   • Reduce pressure to working pressure (typically 1.5 to 2.0 bar) and leave for 24 hours
   • Record pressure at the start and end of the 24-hour period
   • A pressure drop of more than 0.2 bar indicates a leak — investigate and retest
6. Record and sign off
   • Complete the pressure test record with: date, test pressure, start reading, end readings at each interval, and signature of the competent person conducting the test
   • Submit the signed test record to the principal contractor

Why Air Pressure Testing is Prohibited

This point must be explicitly stated in your RAMS and method statement. Air pressure testing of UFH water pipework is prohibited because:

• Water is incompressible — when a water-pressurised pipe fails, the energy released is limited to the localised water volume at the failure point
• Air is compressible — when an air-pressurised pipe fails, the stored energy in the compressed air column is released instantaneously, causing an explosive failure that can propel fittings, pipe sections, and water at high velocity
• A pipe failure under 6 bar of air pressure at 20°C stores significantly more energy than the same failure under 6 bar of water — the potential for serious injury is dramatically higher

Your RAMS must state: "UFH pipework shall be hydraulically tested using clean water only. No pneumatic (air) pressure testing of water pipework is permitted under any circumstances."

Screed Contractor Interface Controls

UFH pipe must remain pressurised during the screed-laying operation to:

• Maintain pipe shape (pressurisation prevents pipe collapse under the weight of wet screed)
• Enable immediate detection of pipe damage during screed laying (pressure loss indicates pipe has been damaged by the screed contractor's equipment)

Your RAMS must specify the interface protocol:

• UFH contractor to brief screed contractor before screeding begins on the pressure test status, working pressure, and the procedure for detecting and reporting pressure loss
• Screed contractor to notify UFH contractor immediately if pressure drops significantly during screeding
• UFH contractor or their representative to attend site during the screeding operation (or be available on call)
• No screed to be laid over any section of UFH pipe that has not been pressure tested and signed off

What Your Method Statement Must Cover

• Manifold installation sequence: bracket fixing, assembly mounting, loop connections, actuator installation, electrical interface
• Pressure test procedure: pre-test checks, fill and purge, pressurisation, hold test, extended working pressure test, records
• Explicit prohibition on air pressure testing
• Gauge calibration: specification and calibration certificate requirement
• Screed contractor interface: briefing, pressure monitoring during screeding, attendance or on-call arrangement
• Test record format and submission process

Frequently Asked Questions

Can we use a digital pressure gauge for the UFH pressure test?

Yes, provided the gauge has a valid calibration certificate from an accredited calibration laboratory. Digital gauges with data logging capability are particularly useful for the 24-hour extended test, as they provide a continuous record of pressure rather than manual readings at set intervals. This makes it easier to identify the timing and rate of any pressure drop. Retain the calibration certificate and include it with the test record submitted to the principal contractor.

What should we do if the UFH pipe is damaged during screeding?

Stop screeding immediately around the damaged area. The damaged section must be excavated from the partially laid screed, repaired (or the loop section replaced), and pressure tested again before screeding resumes over that area. Document the incident, the repair, and the retest result. Report the incident to the principal contractor. If the damage is the result of the screed contractor's negligence, this is a contractual matter between the principal contractor and the respective subcontractors — your priority is to ensure the pipe is repaired and tested before it is permanently encased in screed.

At what point can the UFH system be commissioning-balanced?

Commissioning balancing (setting individual loop flow rates to achieve design conditions) should be carried out after the heating source (boiler or heat pump) is installed and commissioned, and after the building envelope is sufficiently complete to allow the building to be heated to operating conditions. Balancing UFH flow rates before these conditions are in place will produce inaccurate results. Most UFH commissioning takes place during the final mechanical commissioning phase of the project, typically 4 to 8 weeks before practical completion.