Plumbing and Sanitary Installation Inspection

In accordance with UNI 9182 (hot and cold water supply systems — design, installation and testing), UNI EN 806-2 (design), UNI EN 806-3 (pipe sizing) and UNI EN 806-5 (operation and maintenance). Pipe materials must comply with the relevant standards: multilayer (UNI EN ISO 21003), copper (UNI EN 1057), stainless steel (UNI EN 10312) or PP-R (UNI EN ISO 15874). System design pressure is typically 6 bar for residential buildings. Minimum flow rates and pressures at outlets must comply with UNI 9182 Table 1 (e.g., 0.10 l/s at 50 kPa for a wash basin).

1. Verify pipe material, diameter and routing against the approved design drawings — check that materials carry the required product markings and CE/UNI conformity

2. Inspect pipe supports and fixings — maximum spacing per material standard (e.g., 1.2 m for 20 mm copper horizontal, 1.8 m for 25 mm multilayer) with provisions for thermal expansion

3. Check that isolation valves (valvole di intercettazione) are installed at each riser, each apartment entry and each appliance group as required by UNI 9182

4. Verify that pipes passing through walls and floors have protective sleeves (controtubi) and that the annular space is sealed with fire-resistant material where required

5. Measure static water pressure at the most remote and highest outlet — minimum 100 kPa (1 bar) dynamic pressure at any outlet per UNI 9182

- Pipes undersized for the number of outlets served, resulting in inadequate flow and pressure at upper floors

- Missing isolation valves at apartment entries, making maintenance impossible without shutting down the entire riser

- Thermal expansion not accommodated, causing pipe stress, joint failure and noise (water hammer)

- Dissimilar metals connected without dielectric fittings, leading to galvanic corrosion

- Pipe sleeves omitted at fire compartment penetrations, compromising fire resistance

In accordance with UNI EN 12056-2 (gravity drainage inside buildings — sanitary pipework), UNI EN 12056-3 (roof drainage) and UNI 9183 (external drainage and sewerage). Waste pipe gradients must comply with UNI EN 12056: minimum 1% (1:100) for pipes ≥100 mm diameter and 1.5% for smaller pipes. All sanitary appliances must be connected via a trap (sifone) with a minimum water seal depth of 50 mm per UNI EN 12056-2. Vent pipes are required per UNI EN 12056-2 to prevent trap siphonage.

1. Verify pipe gradients using a spirit level or laser — minimum 1% for 100 mm pipes and 1.5% for smaller diameters; maximum 5% to avoid solid deposition

2. Check that every sanitary appliance has a functioning trap with minimum 50 mm water seal — verify trap type is appropriate (e.g., bottle trap for basins, P-trap or S-trap for WCs)

3. Inspect all joints for water tightness — solvent-welded PVC joints must be fully bonded, push-fit joints must have the rubber seal correctly seated, and no joints should be within the floor/wall structure without access

4. Verify that vent pipes (colonne di ventilazione) are installed and terminate above roof level or connect to an air admittance valve (AAV) where permitted by UNI EN 12056-2

5. Check that clean-out access points (tappi d'ispezione) are provided at changes of direction, junctions and at regular intervals per UNI 9183

6. For rainwater drainage, verify that downpipe sizing matches the roof catchment area calculation per UNI EN 12056-3

- Insufficient pipe gradient causing slow drainage, blockages and solid deposition in horizontal runs

- Traps siphoned due to missing or inadequate ventilation, allowing sewer gases into the building

- Waste connections made without traps, permitting foul odours and potentially harmful gases to enter habitable spaces

- Clean-out points omitted or inaccessible, making blockage clearance extremely difficult

- Drainage pipes not acoustically isolated from the building structure, transmitting noise to adjacent rooms

In accordance with UNI 9182 (hot water systems), UNI EN 806-2 and the Italian Legionella prevention guidelines (Linee guida per la prevenzione e il controllo della legionellosi — Conferenza Stato-Regioni 07/05/2015). Hot water storage must maintain a minimum temperature of 60°C at the boiler/storage vessel and deliver a minimum of 50°C at the point of use to prevent Legionella colonisation. Hot water distribution systems in buildings with centralised production must incorporate recirculation (ricircolo) to maintain temperature. Anti-scald protection (maximum 48°C) is required at outlets accessible to children and vulnerable persons per D.M. 236/1989.

1. Measure stored hot water temperature at the boiler or storage cylinder — minimum 60°C to inhibit Legionella growth as per Italian health guidelines

2. Measure hot water temperature at the most remote outlet — minimum 50°C within 30 seconds of opening the tap; if below, the recirculation system may be inadequate

3. Verify that thermostatic mixing valves (TMVs) are installed at outlets serving vulnerable users — maximum delivery temperature 48°C at the outlet per D.M. 236/1989

4. Check that dead legs (tratti morti) in the hot water distribution are minimised — no dead leg should exceed 3 litres volume per UNI EN 806-2

5. For centralised hot water systems, verify the recirculation pump operates continuously or on a timer that maintains temperature, and that a balancing valve is installed on each recirculation loop

- Hot water storage temperature set below 60°C to save energy, creating conditions favourable for Legionella proliferation

- Dead legs in the distribution system where stagnant water remains at ambient temperature, providing a breeding ground for Legionella

- Missing or failed thermostatic mixing valves, exposing users to scalding risk

- Recirculation system not balanced, resulting in hot water reaching some outlets quickly but not others

In accordance with D.Lgs. 192/2005 (energy performance of buildings — implementing EU Directive 2002/91/CE), D.M. 26/06/2015 Appendix B (minimum insulation thickness for piping) and UNI EN ISO 12241 (thermal insulation for building equipment). All hot water, heating and cooling pipes must be insulated to reduce energy losses. Minimum insulation thickness depends on pipe diameter, fluid temperature and insulation thermal conductivity (reference λ = 0.040 W/mK). Cold water pipes in unheated spaces must be insulated to prevent condensation and freezing.

1. Verify that all hot water and heating pipes are insulated continuously, including at valves, fittings and supports — check that insulation thickness meets the minimum values in D.M. 26/06/2015 Appendix B (e.g., 30 mm for pipes up to 32 mm diameter at λ = 0.040)

2. Inspect insulation at pipe supports — ensure that thermal bridges are not created by metal clamps compressing the insulation directly against the pipe; use insulated support shoes

3. Check that cold water pipes in unheated spaces (garages, cellars, roof voids) are insulated to prevent freezing — minimum 13 mm closed-cell insulation for frost protection

4. Verify that insulation joints are sealed with vapour-tight adhesive tape on cold pipes to prevent condensation forming under the insulation

5. For pipes in exposed locations, check that insulation is protected with a durable outer cladding (aluminium or PVC jacket) resistant to UV and mechanical damage

- Insulation missing at valves, fittings and pipe supports, creating thermal bridges that account for significant energy losses

- Insulation thickness below the minimum required by D.M. 26/06/2015, resulting in non-compliance and wasted energy

- Vapour barrier not sealed on cold pipe insulation, allowing condensation under the insulation that leads to corrosion and mould

- Insulation damaged during construction and not repaired before walls/ceilings are closed

In accordance with UNI EN 806-4 (specifications for installations inside buildings carrying water for human consumption — installation) and UNI 9182. All water supply pipework must be pressure tested before being concealed (buried in screeds, chased into walls or enclosed in partitions). The test pressure is 1.5 times the maximum design operating pressure, with a minimum of 10 bar, held for a minimum of 30 minutes. No drop in pressure is permitted. Drainage systems must be tested per UNI EN 12056-2 by filling with water to the top of the highest stack and checking for leaks.

1. Confirm that the pressure test is carried out before any pipework is concealed — pipes must be visible and accessible during the test

2. Verify test pressure: minimum 1.5 times the design pressure or 10 bar (whichever is greater) per UNI EN 806-4; check the manometer calibration certificate

3. Monitor the test manometer for the full 30-minute duration — no pressure drop is acceptable; any drop indicates a leak that must be located and repaired

4. For drainage systems, verify that the system is filled with water to the top of the stack and all joints are inspected for leaks after a minimum of 15 minutes

5. Obtain a signed pressure test certificate from the installer, recording the date, test pressure, duration, result and the name of the responsible person

- Pressure test not performed before pipes are buried in screed or concealed in walls, making leak detection and repair extremely difficult and costly

- Test pressure too low or test duration too short, failing to reveal slow leaks at joints

- Manometer not calibrated, giving inaccurate readings and a false-pass result

- Pressure test passed but pipes subsequently damaged during other trades' work (e.g., electrician drilling through a pipe), requiring re-testing

In accordance with UNI EN 1717 (protection against pollution of potable water — backflow prevention) and UNI 9182. Backflow prevention devices must be installed to protect the potable water supply from contamination by back-siphonage or back-pressure. The type of device required depends on the fluid category (1 to 5 per EN 1717). Common requirements: Type AA air gap at storage tanks, Type EA verifiable check valve at boiler fill connections, Type BA reduced-pressure zone (RPZ) valve for high-risk connections. Every building must have a check valve (valvola di non ritorno) at the point of supply entry.

1. Verify that a check valve or backflow preventer is installed at the building's water supply entry point, immediately after the water meter, as required by UNI EN 1717

2. Check that each cross-connection risk point has the appropriate backflow prevention device for its fluid category — e.g., Type AA air gap for WC cistern overflow, Type EA for heating system fill, Type BA for irrigation connections

3. Inspect hose connection points (bidet sprays, garden taps, washing machine connections) for backflow protection — a minimum Type EB or EC device is required per EN 1717

4. Verify that air gaps at storage tanks and cisterns comply with the minimum distance requirement — Type AA air gap must be at least twice the pipe diameter, minimum 20 mm

5. For RPZ valves and other testable devices, confirm that the installer has tested the device and provided a test certificate; verify that annual testing is scheduled in the maintenance plan

- No backflow prevention at the building entry, risking contamination of the public water supply

- Garden tap or irrigation system connected without backflow protection, allowing pesticides or fertilisers to back-siphon into the potable supply

- Air gap at storage tank reduced or eliminated by modifications, removing the primary backflow protection

- Testable backflow devices (RPZ valves) installed but never tested or maintained

In accordance with UNI 7129 (installations for the distribution and use of combustible gases — domestic and similar installations) and UNI 7131 (LPG installations). Gas installations must be carried out by a qualified installer holding the requisite authorisation under D.M. 37/2008 (Article 1, letter e). All gas pipes must be visible or installed in ventilated ducts; buried gas pipes require cathodic protection or polyethylene material (UNI EN 1555). Rooms containing gas appliances must have permanent ventilation openings sized per UNI 7129 Part 2 (minimum 6 cm² per kW of installed power for Type B appliances).

1. Verify that the gas installation has been carried out by an installer qualified under D.M. 37/2008 for gas systems (letter e) — request the installer's qualification certificate

2. Check gas pipe material and routing — copper (UNI EN 1057), steel (UNI EN 10255) or stainless steel (UNI EN 10312) for internal runs; pipes must be visible or in ventilated ducts, never buried in walls or floors without proper protection

3. Inspect ventilation openings in rooms with gas appliances — verify the free area meets UNI 7129 Part 2 requirements (minimum 100 cm² for Type B appliances up to 16 kW; 6 cm² per kW above 16 kW)

4. Verify gas pipe tightness test — the installer must pressure test at 100 mbar for 15 minutes (low-pressure systems) with no pressure drop per UNI 7129 Part 1

5. Check that a gas shut-off valve (rubinetto generale) is accessible at the building entry and at each apartment, and that an emergency shut-off device is provided at each appliance

6. Confirm that the Dichiarazione di Conformità (DiCo) per D.M. 37/2008 has been issued for the gas installation, listing the standards applied (UNI 7129/7131)

- Ventilation openings undersized or blocked, creating a risk of carbon monoxide accumulation from incomplete combustion

- Gas pipes buried in walls without protective sleeves or ventilated ducts, making leak detection impossible

- Flexible gas connections (tubi flessibili) exceeding the maximum length of 2 m or not secured against accidental disconnection

- Gas tightness test certificate missing or test not performed, leaving undetected leaks in the system

- DiCo not issued by the installer, leaving the building owner without the legally required compliance declaration