Plumbing and Sanitary Installation

Drinking water supply installations must comply with DIN 1988-200 (DVGW Technical Rule W 551) and DIN EN 806 series. Pipe sizing must be calculated in accordance with DIN 1988-300 to ensure adequate flow rates and pressure at all draw-off points while avoiding oversizing that promotes stagnation. Materials in contact with drinking water must hold KTW (Kunststoffe im Trinkwasser) or W 270 approval. The installation must maintain hygiene principles — shortest possible pipe runs, avoidance of dead legs and stagnation sections. The system must provide minimum 1.0 bar flowing pressure at the most remote draw-off point.

1. Verify pipe sizing calculation per DIN 1988-300 — adequate flow rates (minimum 0.07 l/s per fixture) and pressure (minimum 1.0 bar at remote draw-off)

2. Check pipe materials hold valid KTW or DVGW certification for drinking water contact

3. Inspect for dead legs and stagnation sections — no unused pipe branches exceeding 3 litres volume (DVGW W 551)

4. Verify pipe routing follows shortest practical path with correct fall on horizontal runs

5. Confirm isolation valves are accessible and correctly positioned for maintenance and emergency shut-off

- Oversized pipes causing slow flow velocities and stagnation, promoting bacterial growth

- Dead legs from abandoned or capped-off pipe branches exceeding the 3-litre volume limit

- Pipe materials without valid DVGW/KTW certification used in drinking water systems

- Insufficient pressure at remote fixtures due to undersized supply pipes or excessive pressure losses

Gravity drainage inside buildings must comply with DIN EN 12056 Parts 1-5, with DIN 1986-100 covering drainage on private ground up to the public sewer connection. Germany applies System I (single stack with partly filled pipes) per DIN EN 12056-2. Pipe gradients must be between 1:50 (0.5 cm/m minimum for DN 100) and 1:20. Trap seals must be minimum 50 mm water depth. Ventilation of the drainage system must comply with DIN EN 12056-2 Section 6 to prevent trap seal loss from siphonage. Access points for cleaning must be provided per DIN EN 12056-1 at changes of direction and at maximum intervals.

1. Verify pipe gradients — minimum 0.5 cm/m (1:200) for DN 50, 1.0 cm/m (1:100) for DN 70-100, maximum 5.0 cm/m per DIN EN 12056-2

2. Check trap seal depth — minimum 50 mm water seal at all fixtures per DIN EN 12056-2

3. Inspect ventilation provisions — stack vent extended above roof or air admittance valves where permitted

4. Verify access and cleaning points are provided at changes of direction exceeding 45° and at intervals per DIN EN 12056-1

5. Confirm pipe materials and jointing comply with the respective product standards (EN 1451 for PP, EN 1329 for PVC-U)

- Pipe gradient too steep (exceeding maximum) causing solids to be left behind as water runs away too fast

- Missing or insufficient ventilation causing trap seal loss and sewer gas entry into the building

- Cleaning access points omitted at bends and junctions, preventing future maintenance

- Trap seals below 50 mm depth or self-siphoning traps installed

- Incorrect pipe diameter used for the connected fixture units

Hot water systems must comply with DVGW W 551 for Legionella prevention and DIN 1988-200 for system design. Storage water heaters must maintain a minimum temperature of 60°C at the heater outlet. The return temperature in circulation systems must not fall below 55°C. The temperature at any draw-off point must reach 55°C within 30 seconds of opening. Systems with storage volumes exceeding 400 litres or pipe volumes exceeding 3 litres between the heater and the most remote draw-off point are classified as large-scale installations and require annual Legionella sampling per TrinkwV (German Drinking Water Ordinance). Circulation pumps must operate continuously or on a timer with a maximum off-period as defined in DVGW W 551.

1. Measure water heater outlet temperature — minimum 60°C at the storage heater outlet per DVGW W 551

2. Check circulation return temperature — must not fall below 55°C at any point in the circulation loop

3. Verify draw-off temperature at the most remote fixture — must reach 55°C within 30 seconds of opening

4. Confirm system classification (small-scale or large-scale) based on storage volume and pipe content thresholds

5. Review Legionella sampling records for large-scale installations — annual testing per TrinkwV with results below 100 CFU/100 ml

6. Check that circulation pumps operate continuously or with controlled timer schedules per DVGW W 551

- Water heater set below 60°C to save energy, creating ideal conditions for Legionella growth

- Circulation return temperature below 55°C due to undersized circulation pump or unbalanced loop

- Dead legs and rarely used branches not flushed regularly, creating stagnation zones

- Large-scale installation not registered for mandatory annual Legionella sampling

- Missing thermostatic mixing valves at draw-off points where scald protection is required

Pipe insulation must comply with the German Building Energy Act (GEG, formerly EnEV) Annex 8. All accessible hot water and heating pipes in unheated areas must be insulated. The minimum insulation thickness depends on the pipe diameter and the thermal conductivity of the insulation material — for pipes up to DN 22, the insulation thickness must equal at least the pipe outer diameter (100% rule) when using material with a thermal conductivity of 0.035 W/mK. For pipes in wall chases and floor voids, a minimum of 50% of the standard thickness applies. Cold water pipes must be insulated to prevent condensation and to maintain drinking water hygiene by keeping temperatures below 25°C per DVGW W 551 and DIN 1988-200.

1. Verify insulation thickness on hot water and heating pipes — minimum 100% of pipe outer diameter for accessible runs in unheated areas per GEG Annex 8

2. Check that insulation is continuous with no gaps at valves, fittings, pipe supports and penetrations

3. Inspect cold water pipe insulation — confirm insulation prevents condensation and keeps water temperature below 25°C

4. Verify insulation material thermal conductivity matches the design assumption (typically 0.035 W/mK reference value)

5. Check that insulation is protected from mechanical damage and UV exposure in exposed locations

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

- Insufficient insulation thickness — 50% rule applied to accessible pipes where 100% is required

- Cold water pipes uninsulated in warm zones, allowing water temperature to exceed 25°C and promoting Legionella risk

- Insulation joints not sealed, allowing moisture ingress and reducing thermal performance

- Wrong insulation material used for the application (e.g. non-vapour-tight insulation on cold pipes)

Pressure testing of drinking water installations must comply with DIN EN 806-4 and ZVSHK installation guidelines. Two test methods are accepted: the standard pressure test with water and the dry test with compressed air or inert gas for frost-risk situations. For the water test, the system is filled, bled of air and pressurised to 1.5 times the maximum operating pressure (minimum 10 bar) for a holding period. The test pressure must remain stable within permitted tolerances — maximum pressure drop of 0.1 bar over 30 minutes for the final test. All joints, connections and fittings must be visible and accessible during the test. A written test protocol must be completed and signed by the installer and the supervising engineer.

1. Verify test pressure — minimum 1.5 times the maximum operating pressure or 10 bar, whichever is greater per DIN EN 806-4

2. Confirm holding period — no significant pressure drop (maximum 0.1 bar) over the specified 30-minute final test period

3. Check that all joints, connections, press fittings and solder joints are visible and accessible during the test — no concealed connections untested

4. Review the written test protocol — date, test pressure, duration, pressure readings and signatures must be documented

5. Verify the system was properly bled of air before pressurisation to prevent false readings

- Pressure test conducted after pipes are concealed, preventing visual inspection of joints during testing

- Air trapped in the system causing pressure fluctuations and unreliable test results

- Test pressure below the required 1.5 times operating pressure

- No written test protocol produced, making future leak investigation and warranty claims difficult

- Press fittings not fully crimped, passing initial test but failing under thermal cycling

Protection of the drinking water supply against contamination by backflow must comply with DIN EN 1717 and DIN 1988-100. Every connection point to a non-potable system or appliance must be fitted with a backflow prevention device appropriate to the fluid risk category (1-5). Risk Category 5 (health hazard from microbial or chemical contamination) requires a free air gap (Type AA or AB). Category 4 requires a non-return valve with a verifiable check (Type EA). Hose connections below flood level require a pipe disconnector (Type BA or CA). The installer must assess each connection point, document the fluid category and specify the appropriate backflow preventer per DIN EN 1717 Table 1.

1. Identify all connection points to non-potable systems — heating fill loops, garden hoses, washing machines, irrigation systems and industrial processes

2. Verify the fluid risk category assessment for each connection point per DIN EN 1717 Table 1

3. Check that the installed backflow prevention device matches the required type for the assessed risk category

4. Inspect free air gaps (Type AA/AB) — minimum gap must be twice the inlet pipe diameter or 20 mm, whichever is greater

5. Verify that testable backflow preventers (Type BA) are accessible for annual inspection and maintenance

- Heating system fill connection without a system disconnector, allowing contaminated heating water to flow back into the drinking water supply

- Garden hose connections below flood level without appropriate pipe disconnectors

- Free air gaps reduced or eliminated by incorrect installation of overflow pipes or flexible hose connections

- Non-testable devices installed where testable backflow preventers are required

- Missing documentation of fluid category assessment for connection points

Gas installations must comply with DVGW TRGI 2018 (Technical Rules for Gas Installations) and must be carried out by a registered gas installer listed with the local gas supply company (Installationsverzeichnis). The installation includes gas service pipes, gas meters, internal gas pipes, ventilation provisions and connection of gas appliances. Gas pipes must be tested for leak-tightness before commissioning using the prescribed pressure test procedures — usability test at 150 mbar for 10 minutes (no pressure drop permitted). Ventilation openings for gas appliances must comply with DVGW TRGI 2018 requirements based on appliance type (open-flue or room-sealed). A commissioning protocol must be completed and the installation registered with the gas supplier.

1. Verify the installer holds a valid registration in the local gas supplier's Installationsverzeichnis

2. Review the pressure test protocol — usability test at 150 mbar for minimum 10 minutes with no measurable pressure drop

3. Check that all gas pipe joints are accessible for inspection — no concealed joints in inaccessible voids

4. Verify ventilation openings for open-flue gas appliances — minimum free area per DVGW TRGI 2018 based on appliance input rating

5. Confirm that a commissioning protocol is completed and the installation is registered with the gas supply company

6. Inspect gas pipe material and routing — compliance with DVGW TRGI 2018 for material, support spacing and protection from mechanical damage

- Gas installation carried out by an unregistered installer, voiding insurance and warranty

- Pressure test not performed or documented before commissioning

- Ventilation openings undersized or blocked for open-flue gas appliances, creating carbon monoxide risk

- Gas pipes routed through bedrooms or bathrooms without additional protective measures

- Missing gas isolation valve at the meter or before individual appliances