What does a sewer pressure test entail?

What does the pressure testing of sewers involve? Is water better than air for this purpose?

Pressure testing using water is probably the most common method for testing sewer tightness. What are its pros and cons? How is a pressure test performed? Why is pressure testing using air better than using water?

Sewer pressure testing is governed by ČSN 756909 standard which defines the method regardless of the pipe material and the means of installation in collectors or on various structures. This standard also applies to sewage delivery pipes.

All piping used in public utilities must be tested prior to commissioning in order to demonstrate its strength and tightness, and thus its quality and readiness of the entire system regarding the future operation.

Pressure testing of sewers is usually conducted in three stages:

  1. Preliminary pressure test
  2. Pressure drop test
  3. Main pressure test.

If a leak or other undesired changes occur in the pipeline during the pressure test, the test is discontinued and the pipe must be repaired. Once the defects are rectified, the pressure test is repeated from the beginning.

Two types of pressure sewer tests

According to law, pressure testing of sewers can use both water and air. What are the processes and the benefits?

Pressure sewer testing using water – the process

  1. Firstly, the parts of the system to be tested are inspected visually. Service pipe seals are inspected.
  2. Sealing bags are fitted and connected to a water supply.
  3. The sewer section is inspected whilst being filled with water and de-aerated.
  4. A test vessel is fitted and water is topped up to a test level.
  5. The section is inspected and water topped up while the material absorbs it.
  6. The system is checked for any water leaks revealing a sealing problem.
  7. An official record of the pressure test is issued.

Sewer pressure test using air under EN 1610, Chapter 13, method ‘L’ – the process

  1. The sewer section to be tested is visually inspected for its ability to undergo a pressure test, including the tightness of service pipes.
  2. Sealing bags are fitted and connected to an air supply.
  3. The section is pressurised using a compressor, and the pressure must not drop during the test.
  4. Pressure is checked using a pressure gauge and potential leaks are calculated using computer software.
  5. The pressure is relieved and seals removed.
  6. A test record is prepared.

Sewer tightness test using air

This type of testing is now legal and utilises a precise and continuous process. This offers the following benefits:

  • The test is provable, with each measurement recorded with a precise date, time, and section.
  • The measurements are conclusive and their providers lock the test record documents so that they cannot be altered.
  • Expert measurements are easy to navigate with a graphical presentation and description of sewer status.
  • The measurements are compliant with the ČSN EN 1610 and ČSN 75 6909 methodologies.
  • The measurements are taken using computerised technology, which eliminates the risk of human error. Moreover, the readings are extremely precise!

Benefits of pressure sewer testing by air

Even though pressure testing of sewers using water is the most common method, providers are increasingly switching to pressure testing by air – this is because it is better at detecting all types of leaks, minimises damage such as when masonry is compromised and can be implemented all year round, including in the winter.

A safer pressure test that causes no property damage

Although pressure testing of sewers using water can easily identify leaks, the leaks can cause damage; for example, by disrupting electrical installations, being absorbed into material, and so on. Pressure testing using air poses no such risks.

Pressure testing of sewers by air can be performed all year round

New pipes can be pressure tested throughout the year using air, including in winter when temperatures fall well below zero. In addition, it eliminates the risk of creating slippery spots on site. Above all, pressure testing of sewers with air is much simpler and quicker than the water method.