After the lining tube has been pulled in, it is inflated and pressed against the host pipe wall either by air or water pressure. The internal pressure must be selected in such a way that the lining tube remains securely in contact with the host pipe, even if ground water is present.

The internal pressure must be at least higher than the possible external pressure of the ground water. For the host pipe to be rehabilitated, it must be estimated whether it can withstand the required contact pressure.

The contact pressure must be limited upwards so that the composite is not pressurized too much and thus falls below the required design wall thickness.