Leak testing and SC-Contur: testing dry and finding forgotten pressings

Why testing is done dry today

Whoever pressure-tests a drinking-water installation with water has filled it – and a filled installation must go into operation: complete water exchange every three days to VDI 6023 part 1, at the latest every seven days to EN 806. If it stands longer, germs grow in the stagnant water, and an installation once filled can as a rule no longer be drained completely. That is why EN 806-4 requires the leak test to be carried out dry, with oil-free compressed air or inert gas, and the subsequent load test wet only if intended operation follows immediately. For everything else there is the alternative dry load test according to the leaflet of the German ZVSHK or BTGA rule 5.001.

The manufacturers follow this: in its planning manual Viega declares the dry load test permissible for all its installation systems and calls it the standard for building projects executed in lots. The corrosion assessment to EN 12502 that the designer makes beforehand also assumes a dry pressure test. The wet test is not wrong – it is only tied to the condition that water flows immediately afterwards.

How the dry test runs (manufacturer statement Viega)

• Leak test: compressed air or inert gas at 150 mbar; after reaching the test pressure, test time at least 120 minutes for a pipe volume up to 100 litres, 20 minutes longer per further 100 litres.
• Load test dry: at most 3 bar for nominal sizes up to DN 50, 1 bar above DN 50, over 10 minutes – combined with a visual inspection of all joints for tightness.
• Load test wet (if operation follows immediately): test pressure 1.1 times the maximum operating pressure to EN 806-4; test time with metal pipes 10 minutes after temperature equalisation, with plastic pipes preliminary and main test per manufacturer statement.
• Report: the installer records the test as specified by the system manufacturer – the report is part of the handover.

The figures are manufacturer statements for the Viega systems; Sanha, Geberit and the ZVSHK codes of practice give similar values. What governs is always the current instructions for use of the system and the leaflet according to which the test is made.

Unpressed = leaking: SC-Contur, UVUD, press indicator

The visual inspection of all joints is not always possible in practice and seldom economical. That is why there are separate provisions for joining systems with the property unpressed = leaking: a connector that has not been pressed must not happen to be tight during the leak test – it must inevitably leak so that the forgotten pressing shows on the pressure gauge.

Viega SC-Contur: all Viega press connectors carry the SC-Contur, a forced leakage of the unpressed connector over the entire pressure range of the test – dry from 22 mbar to 3 bar, wet from 1 to 6.5 bar, irrespective of the sealing element; Viega guarantees the detection of unpressed joints in dry tests from 22 hPa to 0.3 MPa and in wet tests from 0.1 to 0.65 MPa. According to the manufacturer the property was tested by the DVGW and by the German public insurers' institute for loss prevention and loss research. A cylindrical pipe guide protects the sealing element during insertion.

Sanha UVUD: Sanha calls the property “unverpresst undicht” (UVUD, unpressed = leaking): before pressing, joints are visibly leaking during the pressure test, forgotten pressings can be identified reliably – for NiroSan, SANHA-Press, Therm and Heavy Steel Press.

Geberit press indicator: FlowFit makes the pressing visible with a press indicator and has defined leak paths that show the unpressed state during the test.

What the property does not replace: the test itself. An unpressed SC-Contur connector is noticed only if pressure is built up, held and read – and the visual inspection remains mandatory for everything that does not have this property.

What is different with threads, push-fit and couplings

Threaded joints and unions must, according to the manufacturer, be checked by hand: an investigation has shown that they cannot be reliably checked centrally, neither with a dry nor with a wet test, neither at low nor at high pressures – an insufficiently tightened thread can be tight at 150 mbar and drip at 6 bar. At every transition to malleable iron or stainless-steel threaded fittings the joint therefore belongs in the visual inspection.

Push-fit systems (GF iFIT) have no pressing that could be missing; their check is the visible insertion depth (mark on the pipe, inspection window on the fitting) and the leak test as with every system. Two O-rings and the pull-out protection take over what bead and deformation do in a press system.

Grooved couplings (Victaulic) are mechanical joints: seat of the coupling in the groove, tightening of the bolts (manufacturer statement on torque) and metal-to-metal contact of the coupling halves are visible from outside; the leak test follows the rules of the plant (sprinklers: VdS, industry: operator).

For all of them: test before plastering, insulating or grouting. A joint you can no longer see can only be measured.

Further reading

Tools of this section: System finder (which system suits medium, pipe and size) · Joining methods compared · Cost comparison calculator · Press systems overview.

The cross-cutting topics: Mixed installation and corrosion · Press profiles and tools · Seals and media · Zeta values of press connectors