The advanced condition assessment of large profiles is applicable in man-accessible sewers made of masonry, cast in place concrete or factory pre-fabricated pipes that are visibly damaged and/or where their load bearing capacity does no longer meet the present or future requirements. The standardised approaches for the acquisition of the condition of drains and sewers made of factory pre-fabricated pipes that were explained in the previous sections …

As a part of the extended condition assessment and in addition to a visual inspection, the geometry and the material constants of the sewer made of masonry as well as the operational limiting conditions that represent the influencing parameters for the rehabilitation planning were determined in detail, they include [ [Borch2007]]:

• A visual inspection and damage acquisition ( (Direct visual inspection of drains and sewers))
• Test drilling to determine …

The extended subsoil investigation served to acquire the geological and hydrogeological conditions, aiming at an adequate subsoil evaluation for structural calculations as well as for further rehabilitation planning (Image 4‑117). The following tests and analyses formed part of the extended subsoil investigation:

• Acquisition of the thickness and sequence of the individual soil layers in the area of the trial pit by means of dynamic core probing to …

Based on the results of the above-mentioned research project, the company S & P Consult GmbH, Bochum, Germany, developed an “Extended investigation and rehabilitation programme for large profile sewers in six steps”, which has established and proven itself in practice [ [FI-S&PCon]]. This programme can be applied for all man-accessible sewers, regardless of their material, cross sectional shape, depth position, condition as well as all other relevant …

According to EN 752 [ [EN752:2017]], environmentally relevant analyses have the objective to determine the environmental impacts of sewage when it leaks from the drain and sewer system depending on its composition and leakage potential.

In this context, these analyses serve to detect [ [EN752:2017]]:

• the effects of leaking drains and sewers on the ground water composition. Drains and sewers in protected or vulnerable groundwater areas that convey …

In accordance with EN 752 [ [EN752:2017]], drain and sewer systems have to be durable, fail-safe and leakproof. The latter requirement means that, in order to avoid an impermissible pollution of the groundwater or an unwanted dilution of the sewage, substances must not enter the groundwater and the groundwater must not be discharged together with the sewage.

To implement this requirement, drain and sewer systems must only be built, operated and maintained …

As a general rule, the subsequently introduced preparatory measures for the execution of a leak tightness testing apply for all methods of testing listed in (Theoretical background on leak tightness testing), Image 4‑124.

(Image: Applicable standards and regulations for leakage testing in the Federal Republic of Germany)

Planning documents

The client has to provide sufficient planning documents for the planning, preparation and execution of the leak …

Theoretical background on leak tightness testing

In all methods that are used for leak tightness testing, the measurement tasks are either limited to:

• the acquisition of the time period within which a certain change in pressure is created, or
• the acquisition of the required quantity of water that has to be added to keep up a constant test pressure.

That means that a certain test media loss is tolerated in all testing methods. The definition of the …

Air pressure testing

The equation that is used for air pressure testing is based on the assumption that an air mass flow escapes through a leak in a defined period of time, resulting in a reduction of pressure (also called pressure loss) in the pipe to be tested. This can be calculated under the assumption of an isentropic and adiabatic flow, that is, during the flow there is neither a loss due to friction nor is there a heat exchange between the …

Due to the different physical properties of the test media (water as an incompressible medium versus air as a compressible medium), the results of leak tightness testings with different test media cannot be directly compared to each other. The determination equations described in the text above are formulated with reference to the leakage area A_L. This allows for a preparation of the results of leak tightness testings with different test media in …

Leak tightness testing of drains and sewers - Testing along entire sections

The principle of a section-wise leak tightness testing of drains and sewers is illustrated in Image 4‑128. The section is blocked at both ends by means of sealing elements that are equipped with connections for compressed air to inflate the individual rubber seals of the sealing elements, to fill the test volume with the test medium, to ensure its venting as well as for pressure …

Pressure testing using water as the test medium represents the classical method of leak tightness testing ( (Theoretical background on leak tightness testing)).

If the water loss during testing exceeds the permissible limit value, the causes have to be identified and eliminated. Then, the test is to be repeated (Image 4‑143).

(Image: Flow chart Water pressure testing – Method “W” in accordance with EN 1610)

In the context of the limiting conditions …

Compared to water pressure testing, leak tightness testing with air as the test medium ( (Air pressure testing, Vacuum testing)) has the following advantages [ [FI-Hydro]]:

• The test section is not filled with water, but with air, so that there are no problems related to water supply and water damages due to sudden pipe breaks.
• Irrespective of the gradient the whole test section is put under a constant test pressure.
• Fast installation of the test …

In leak tightness testing ( (Air pressure testing, Vacuum testing)), a vacuum (negative pressure) is applied to the sewer section or the part of the sewer section to be tested. If there exists a leakage, an increase in pressure (∆p) will occur that, amongst other things, depends on the type and extent of the damage as well as on the type of medium that enters the sewer section through the damaged spot (air, water or a mix of both).

Compared to leak …

For sewers operated under gravity, the leak tightness testing explained in previous sections can be replaced by a visual “testing for infiltration with case-related specifications” by means of a visual inspection ( (Direct visual inspection of drains and sewers)) or a sewer TV inspection ( (Indirect visual inspection of drains and sewers)), if the groundwater level is demonstrably above the pipe crown. Suggestions for the verification of the groundwater …

A special form of testing for infiltration is the infiltration measurement: This method is standardised in the USA in the ASTM-Standard C 1091-90 – 03a (2008) Standard “Test Method for Hydrostatic Infiltration Testing of Vitrified Clay Pipe Lines” [ [ASTMC109190]] for the final acceptance of newly laid gravity sewers made of vitrified clay.

The test according to [ [ASTMC109190]] is carried out on backfilled piping under the condition that the groundwater …

The method of leak tightness testing for individual sectors of sewer sections is applied analogously to section-wise leak tightness testing ( (Leak tightness testing of drains and sewers – Testing of sockets)). The sealing elements, for example, are connected to each other by means of a chain that is adjusted in its length to the length of the sector to be tested and pulled into the required position either manually or by means of a cable winch (…

In the testing or final acceptance of existing or recently rehabilitated drains and sewers, section-wise leak tightness testing is not always economically viable or technically possible. The reasons can be found, for example, in the existence of integrated building connections or connection sewers for non-accessible cross sections, the need for a large water quantity to fill the entire section in the case of larger, man-accessible cross sections …

In EN 1610 [ [DINEN1610: 2015]], the testing of joints with water as the test medium is only described for newly laid or recently rehabilitated drains and sewers. According to that standard, the testing of joints has the same test requirements, i.e. the same water addition values and testing times, as in section- or sector-wise leak tightness testing (Image 4‑164).

(Image: Leak tightness testing of individual pipe joints in newly laid or recently …

In leak tightness testing by means of a compressible medium under pressure (e.g. air), the pressure decay does not only depend on the geometrical dimensions of the leakage, but primarily on the air volume within the section under test and the testing time. These dependencies are also the same for leak tightness testing by means of vacuum. Thus, test results that have been achieved that way are only significant and comparable, if they are referenced …