Best Practice Procedure

Here is a brief run down of the best practice process when performing a new mains chlorination. and we have a number of frequently asked questions below.

Hopefully this will help you understand how a mains chlorination should be performed and ensure that you can obtain a quality service from any contractor you choose to use. Clearly we would like it to be us but we appreciate we aren’t the only brilliant company out there but please be mindful of the unscrupulous companies who really haven’t got the correct skills or qualifications to perform the works to the correct standard.

Mains Chlorination Frequently asked Questions!

Do I really need to swab the pipe?

In reality no, but if you are performing a pressure test then it makes it much safer and it also ensure that dirt and debris are removed from the pipe work so why wouldn’t you for the very small cost of the swab itself?

Do I really need a pressure test?

This depends on which Water Authority is making the connection. Some Water Authorities such as United Utilities insist on a pressure test whilst for others it isn’t an absolute requirement. However, bear in mind a 15 litre per minute leak means around 7.8 million litres of lost water and if you are on a meter then this is a huge cost.

It is much cheaper to include a pressure test at the time of mains chlorination so it just makes sense.

How Sensitive are Our Pressure Tests?

Our Pressure Tests Are Super Sensitive!

We are often asked just how sensitive are our pressure tests and the answer is very, very sensitive.

Using the highest specification equipment, routinely calibrated and having experienced engineers means you can be assured that we will find the leaks.

This is good because the one thing about leaks is that they only ever get bigger. Over time water erodes away the areas around the leak and the leak keeps growing and growing and growing.

What started out as a weep becomes a trickle which then becomes a stream and eventually if left can result in total pipe failure.

Our pressure tests will determine tha slightest weep and our engineers can help locate the leak resulting in a fix prior to the connection and any future problems. Nobody likes a leak but better to find them before the cost of back filling and reinstatement.

What are the Pipe Pressure Testing Standards

There are a number of standards quoted for hydrostatic pressure testing of pipes but the actual standard used can vary depending on a number of factors such as material of pipe, water authority requirements and the size and SDR of the pipe to be tested.

The main standards for testing of pipes are as follows:

WIS 4-01-03. This was released in March 2024 and covers the hydrostatic pressure testing of new PE pipes. It replaces the IGN 4-01-03 for PE mains testing.

IGN 4-01-03. This has now been replaced by the WIS standard for PE but it still contains much of the standards for the testing of cement lined ductile iron.

BS EN 805:2000. Water supply. Requirements for systems and components outside buildings (currently under review). This has a number of hydrostatic test types but for PE these have been superseded by the WIS 4-01-03.

What is Involved in Mains Pressure Testing

New mains pressure testing is performed using hydrostatic means and is known as hydrostatic pressure testing. To perform a hydrostatic pressure test the new pipe work is first filled with water. This generally requires the use of a foam swab, pushed ahead of the water, to remove air. Air will interfere with the pressure testing process and will produce invalid pressure test certificates that will be rejected by the local water authority.

Water is then added to the pipe to be tested through the use of a pressure test pump and a high precision pressure datalogger records and stores the pressure data for later analysis.

The pressure is measured and recorded for the required test time based on a number of factors and the data is then downloaded and analysed based on the specialist equations laid out in the WIS 4-01-03 or the BS EN 805 to determine if the pressure test is a pass or fail. A pressure test certificate is then created.

Considerations When Performing a New Mains Pressure Test

Pressure Testing Safety

When bringing a main to pressure there is a degree of stored energy and this can be highly dangerous if operatives are unaware of the risks. As such staff performing pressure tests should be trained, experienced and competency checked to ensure they are aware of the health and safety risks. Further details can be found on the HSE Website relating to Pressure Testing Systems.

Pipe Material

The pipe material affects the type of test performed and as such the equipment required. Generally most testing is performed on PE pipes which exhibit viscoelastic effects, that is they stretch under pressure. As such this means that they will lose pressure due to the increased pipe volumes and it requires specific calculations to determine if this pressure drop is due to the presence of a leak or if it is due to the natural elasticity of the pipe work.

As such the testing of PE pipes requires specialist equipment and high accuracy dataloggers that can accurately log and record data at regular intervals. Our dataloggers are configurable to allow us to change the data collection times but generally we have a 5 second logging interval for high accuracy.

This test requires specialist calculations to determine the pass or fail criteria of the data collected.

Ductile iron is generally tested utilising the water added method. As ductile iron has no elasticity the main will not stretch and as such should maintain the pressure to which it is raised. There may be some slight losses and there is an allowable loss rate within the IGN/BS EN 805. The pipe pressure is maintained by pumping and the water added to keep the pipe at this pressure is measured.

This method requires highly accurate flow meters capable of measuring millilitre flow rates.

Water Hygiene

It is important that the potable water status of the main is not forgotten and any equipment or fittings used are clean and only used for potable mains testing. It is also important that water used for filling and swabbing is wholesome.

Standard Test Pressure Requirements

Individual Water Authorities can have different pressure specifications and this can change depending on the pipe type and rating. As such it is important to be familiar with these testing specifications to ensure compliance with any particular water authority requirements. Failure to provide testing to the correct pressure will result in a rejected test and you will be unable to connect your new main to the existing water infrastructure.

Swabbing and Air Removal

Air removal is essential when performing a pressure test as air volumes of greater than 4% mean an invalid pressure test that will not be accepted by the water authority. As such swabbing of the new main must be performed and this requires a mains water supply with adequate flow and pressure to drive the swab.

The presence of air will also increase the pump times as more water will be required (as air compresses) to raise the pressure. This results in increased pump up times and subsequently increased times the main must stand under pressure.

Safety is also a significant consideration with the presence of air. As air compresses under pressure the presence of large amounts of air creates a significant safety issue. Should the main fail and this compressed air be released it will do so explosively and this can result in debris being thrown, at high speed, out of the failure site, causing potentially catastrophic results.

Pumps and Pump Up Times

When adding pressure to the pipe there are a wide range of pressure test pumps that can be used, each with different output capabilities and it is important to choose the correct pump for the main in being tested. This allows pressure rise times to be minimised, raising the pressure quickly and efficiently whilst also ensuring that rise times are not too fast, which can make analysis of the test data difficult.

Choosing the correct pressure test pump is important as pressure test run times are calculated from a calculation of the time taken to raise the pipe from static pressure to the required test pressure multiplied by 20. As such a pump time needs to be minimised as otherwise long test times are required which increases labour costs through additional time on site.

To alleviate this issue some contractors can be tempted t pre-pressurise the main from the mains water supply but this is forbidden under the WIS and will be obvious on graphs and data, resulting in an invalid test and the requirement to repeat the works,

Dataloggers and Pressure Gauges

Dataloggers need to be accurate and recently calibrated to ensure they are accurate and are measuring the correct pressures. For PE pipes they are generally set to record data at 20 second intervals but more accurate dataloggers can be programmed. We set our dataloggers to provide a pressure data point every 5 seconds, allowing for highly accurate analysis.

The ability to see graphs as they are created will also allow fast indication of a pass or fail and will allow any required remedial work to be performed on the pipework to ensure a pass can be obtained.

Mains Pressure Test Certification

The pressure testing certificate needs to contain a number of things to ensure it meets the water authority requirements and meets the WIS 4-01-03 standards (or the ductile iron testing requirements). The certificate should contain as a minimum the following:

Date of the pressure test
Engineer performing the pressure test including their EUSR water hygiene card number
Location of the pressure test including ideally the GPS co-ordinates
The details of the pipes tested including the SDR, length and OD as well as the total volume of the system
The standard test pressure
The amount of water added to raise the pressure from static pressure to the standard test pressure
A calculation to show the amount of air present in the pipe (this MSUT be less than 4% for a valid test)
The logarithmic calculations showing the N1/N2 ratio and the PASS or FAIL status of the pipe
The pressure vs time graph
The logarithmic N1/N2 graph showing ideally a straight line
The raw data from the datalogger

Ideally all the above will be provided in a single document for ease of provision to the water authority so that they can signal a pass and the new water pipes can be connected to the mains.

Chlorination

Generally the next stage after any mains pressure test is a chlorination of the tested pipe work to ensure it is clean and fit for connection to the main. This will include UKAS accredited sampling to ensure no microbiological contaminants are present. The requirements for chlorination are covered in detail in our chlorination page.