Plumbing and Water Supply Installation

CTE DB-HS4 establishes requirements for potable water supply installations in buildings. The installation must guarantee minimum flow rates and pressures at each outlet: 100 kPa minimum at any point of use, maximum 500 kPa static pressure. Pipe sizing must follow the simultaneous use coefficients defined in CTE DB-HS4. Materials must comply with UNE-EN 806 and be suitable for contact with potable water.

1. Verify pipe materials and dimensions match the project specification and comply with UNE-EN 806 for potable water suitability

2. Check that pipe routing, supports, and fixings are correct — horizontal pipes at minimum 0.5% fall towards drain points per CTE DB-HS4

3. Confirm isolation valves are installed at each riser, branch, and individual dwelling as required by CTE DB-HS4

4. Measure water pressure at the most unfavourable outlet — minimum 100 kPa for taps, 150 kPa for thermostatic valves per CTE DB-HS4

5. Verify flow rates at representative outlets meet minimum values specified in CTE DB-HS4 Table 2.1

- Insufficient pressure at upper floor outlets due to inadequate pipe sizing

- Missing isolation valves on branches making maintenance impossible without shutting down the entire system

- Pipe supports too far apart causing sagging and air locks

- Non-certified pipe materials used in potable water installations

CTE DB-HS5 establishes requirements for building drainage installations. Drainage pipes must be sized using the discharge unit method defined in CTE DB-HS5 tables. Minimum pipe gradients are 1% for collectors with diameter 160 mm or less, and 0.5% for larger diameters. All sanitary appliances must connect through a trap with a minimum 50 mm water seal. Ventilation of the drainage network is required per CTE DB-HS5 Section 3.3.

1. Verify drainage pipe sizes match the discharge unit calculations per CTE DB-HS5 Tables 4.1 to 4.5

2. Check pipe gradients with a spirit level or laser — minimum 1% for branch pipes and small collectors per CTE DB-HS5

3. Confirm every sanitary appliance has a trap with minimum 50 mm water seal and that traps are accessible for cleaning

4. Verify the ventilation system is installed — primary ventilation on all soil stacks extending above roof level per CTE DB-HS5

5. Check that all joints are watertight and pipes are properly supported at maximum intervals per material specifications

6. Confirm cleanout access points are provided at changes of direction and at maximum 15 m intervals on horizontal runs

- Insufficient pipe gradient causing slow drainage and blockages

- Missing or inadequate ventilation causing trap siphonage and odour entry

- Traps without access for cleaning leading to persistent blockages

- Drainage pipes not properly tested for watertightness before concealment

- Undersized pipes for the connected discharge units

RD 865/2003 establishes criteria for Legionella prevention in hot water systems. Storage water heaters must maintain water at minimum 60 degrees C throughout the tank. Distribution temperature must be at least 50 degrees C at the furthest point. Return circulation temperature must not fall below 50 degrees C. CTE DB-HE4 requires solar thermal contribution to domestic hot water based on climate zone. Dead legs must not exceed 3 metres from the circulation loop.

1. Measure stored hot water temperature at the heater outlet — minimum 60 degrees C per RD 865/2003

2. Check distribution temperature at the furthest outlet — minimum 50 degrees C at the point of use per RD 865/2003

3. Verify return circulation loop temperature — must not fall below 50 degrees C at any point per RD 865/2003

4. Confirm dead legs from the recirculation loop to each outlet do not exceed 3 metres to prevent Legionella colonisation

5. Check that the system includes thermal disinfection capability — able to raise temperature to 70 degrees C throughout per RD 865/2003

6. Verify solar thermal system is installed and operational where required by CTE DB-HE4 for the climate zone

- Hot water storage temperature below 60 degrees C allowing Legionella growth

- Dead legs exceeding 3 metres creating stagnant water zones for bacterial colonisation

- Missing or non-functional recirculation pump causing temperature drop in distribution

- Solar thermal system not properly integrated with backup heater

RITE (Reglamento de Instalaciones Termicas en los Edificios) IT 1.2.4.2 specifies minimum insulation thickness for hot and cold water pipes based on pipe diameter and whether the pipe runs indoors or outdoors. Hot water pipes must be insulated to reduce heat loss. Cold water pipes must be insulated to prevent condensation and to maintain water temperature below 20 degrees C per RD 865/2003 for Legionella prevention.

1. Verify insulation material and thickness on hot water pipes meet RITE IT 1.2.4.2 minimum requirements for the pipe diameter and location

2. Check insulation on cold water pipes — required where pipes pass through heated spaces or where condensation risk exists

3. Confirm insulation is continuous with no gaps at valves, fittings, supports, or pipe penetrations

4. Verify vapour barrier is intact on cold water pipe insulation to prevent condensation within the insulation

5. Check that insulation is properly secured and finished, with no damage from other trades

- Insulation missing at valves, flanges, and pipe supports creating thermal bridges

- Vapour barrier damaged on cold water pipe insulation causing condensation and dripping

- Insulation thickness below RITE minimum requirements

- Hot and cold water pipes run in contact without insulation between them causing heat transfer

CTE DB-HS4 requires pressure testing of water supply installations before commissioning. The test must be conducted at 1.5 times the maximum working pressure, with a minimum of 1000 kPa, maintained for a minimum of 2 hours with no visible leaks and no pressure drop exceeding 20 kPa. Drainage installations must be tested per CTE DB-HS5 using water fill or air pressure tests. All tests must be witnessed and documented.

1. Verify water supply pressure test is conducted at 1.5 times working pressure (minimum 1000 kPa) per CTE DB-HS4

2. Confirm test duration is minimum 2 hours with pressure monitored and recorded at regular intervals

3. Check that pressure drop does not exceed 20 kPa over the test period — any greater drop indicates a leak

4. Verify drainage system is tested by filling to the top of the highest stack and holding for 30 minutes with no leaks per CTE DB-HS5

5. Confirm all test results are documented with date, test pressure, duration, and results signed by the installer and inspector

- Pressure test conducted at insufficient pressure or for inadequate duration

- Test not witnessed by an independent party

- Leaks at threaded connections and compression fittings discovered during testing

- Test documentation incomplete or missing for building control submission

UNE-EN 1717 classifies backflow prevention devices and specifies their application based on the fluid risk category. CTE DB-HS4 requires backflow prevention at the building connection and at all points where contamination of the potable water supply could occur. Air gaps (Type AA or AB per UNE-EN 1717) provide the highest level of protection. Check valves alone are insufficient for high-risk fluid categories.

1. Verify a backflow prevention device is installed at the building water service entry point per CTE DB-HS4

2. Check that each point of potential contamination has a backflow preventer appropriate to its fluid risk category per UNE-EN 1717

3. Confirm air gaps at storage cisterns and tanks meet minimum requirements — Type AA gap must be at least twice the inlet pipe diameter

4. Verify that heating system fill connections have appropriate backflow prevention (minimum Type CA device per UNE-EN 1717)

5. Check that all backflow prevention devices are accessible for testing and maintenance

- Missing backflow prevention at the building service entry

- Inadequate device type for the fluid risk category — check valve used where reduced pressure zone valve is required

- Air gap at cistern insufficient or bypassed by overflow arrangement

- Backflow devices installed in inaccessible locations preventing routine testing

RD 919/2006 regulates gas installations in Spain, covering design, installation, testing, and commissioning. Gas pipes must be tested at 1.5 times operating pressure (minimum 100 mbar for low-pressure installations). Ventilation requirements must meet RD 919/2006 for appliance rooms — combustion air supply openings sized to the total appliance input rating. Gas detectors and automatic shut-off valves are required in certain occupancies.

1. Verify gas pipe materials, sizes, and routing comply with RD 919/2006 — copper, steel, or approved PE for buried sections

2. Confirm gas tightness test has been performed at the required pressure and duration per RD 919/2006 with no detectable leaks

3. Check that combustion air ventilation openings are correctly sized for the total appliance input rating and are unobstructed

4. Verify gas isolation valves are installed at the meter, at each riser, and at each appliance per RD 919/2006

5. Confirm gas appliance flues are correctly terminated, with adequate clearance from openable windows and air intakes

6. Check that gas installation has been certified by an authorised installer (empresa instaladora autorizada) with documentation submitted to the gas distributor

- Gas pipes not pressure tested or test not properly documented

- Combustion air ventilation openings undersized or blocked

- Gas pipe joints not accessible for leak detection in concealed runs

- Missing gas isolation valve at individual appliances

- Gas installation certificate not submitted to the distributor