Leak testing is one of the very important tasks in any plumbing system work. Failure to do so would result in catastrophic damages especially when the building is already finished.
There are 2 methods of Water Pressure Leak testing:
1. Hydrostatic Pressure Test
2. Air Pressure test
A hydrostatic test is the most commonly used method employed in conducting a pressurized leak test since it is the most practical and could easily be done. While Pressurised Air Test is allowed as stated in Section 501.2.6 of the Revised National Plumbing Code of the Philippines (NPCP), it is a difficult method especially when the leak test fails, it would be too difficult to find the source of the leak since we cannot see air. For this reason, we will focus our discussion on the hydrostatic pressure test method.
How to Hydrostatic Test?
The first consideration in performing the hydrostatic test is by determining the scope of the test. While complete testing could be easily done in small projects, in large and complex buildings, It would be difficult and impractical to do the test one time, big time!
Works on most if not all building projects are programmed and sequenced in such a way as to maximize the time required to finish the project. Other works on the project cannot wait until all the pipes are installed especially when pipes are embedded on walls, ceilings, and below the ground.
When to test?
Hydrostatic testing shall be done while the pipe works to be tested are still visible. This must be planned and discussed in the toolbox meeting onsite. The last thing you wouldn't want to know is the mason had already completely plastered or tiled the walls when the testing is not yet done. For pipes installed on masonry walls, it is important to avoid putting the temporary fixing mortar along joints of pipes since it is where most pipe leaks occur.
Hydrostatic Testing requirements:
As per our revised NPCP, the minimum test requirement for any water piping shall not be less than the working pressure under which it is to be used plus 50%. The piping must withstand the test without leaking for a period of not less than fifteen (15) minutes.
In a perfect world, there would be no allowable leakage. However, as we all know, nothing is perfect. By experience, it would be too difficult to meet a no-leak system. This is the reason why most plumbing designers resort to other leak testing criteria other than the NPCP.
AWWA Standards such as AWWA C600 for ductile iron mains and C605 for PVC mains provide for a table for allowable leakages. A common procedure for testing is in the following table:
Pressure and Leakage Test Requirements
Procedure | Test Pressure | Duration of Test |
|---|---|---|
Simultaneous Pressure and Leakage Test | 150% of working pressure at the point of test, but not less than 125% of normal working pressure at the highest elevation. | 2 Hours |
Separate Pressure Test | 150% of working pressure at the point of test, but not less than 125% of normal working pressure at the highest elevation. | 1 Hour |
Separate Leakage test | 150% of working pressure of segment being tested. | 2 Hours |
The most common criteria of hydrostatic pressure testing are for the piping to be tested under 150% of the calculated working pressure for 2 hours, with an allowable drop of 5 psi. For low-rise projects such as residential and light commercial buildings, especially for those without booster pumps, the most common minimum test pressure is no lesser than 100 psi. However, it is important to determine the actual water main pressure by conducting a 7-day pressure monitoring test to determine the maximum actual pressure from the water main.
For example, if the calculated working pressure of a boosted system is 130 psi, therefore the testing pressure shall be computed as 130 psi x 1.5 = 195 psi.
Step-by-Step procedure in performing a Hydrostatic Test:
1. Prepare a printed Test Form and a drawing of the pipe segment to be tested.
Documentation is of utmost importance in conducting a test because it will serve as a piece of evidence that a pressure test was performed. At a minimum, the test form shall contain the criteria, results, participants, and authorized witnesses by both contractor and owner.
2. Prepare the testing tools and equipment. The following are the basic equipment used in the performance of a hydrostatic test:
a. Pressure Test Pump
There are two kinds of test pumps, the first is a manual test pump which has an integrated bucket filled with water. The other one is an electric test pump which has an electric motor to easily pump water into the system.
b. Pressure Test Manifold
A pressure test manifold is a simple assembly composed of a pressure test gauge, a valve that closes the system, and other fittings to connect it to the piping system as well as to the test pump.
c. Plugs
Plugs are usually of threaded galvanized iron or stainless steel material. It is used to temporarily close all open piping or terminations to fixtures. Do not use melted PPR pipe as some contractors do as it usually would cause leaks and would delay the pipe testing.
d. Basic Plumbing tools such as pipe and hex wrenches.
3. Connect the Test manifold to the piping system, then connect the test pump to the test manifold.
4. Plug all pipe terminations of the pipe system to be tested except the highest termination, open all valves within the pipeline.
5. It is important to extract all the air within the system, the best method is to plug the terminations as the water is filled and comes out of the terminations. In this way, no air is trapped in the pipes being tested as air is compressible and would allow fluctuations in the test readings.
6. Plug tightly all terminations starting from the bottom up to the top of the system until water comes out of the remaining topmost portion. Plug the remaining opening.
7. Increase the pressure using the test pump while observing the piping system being tested, making sure there are no visible leaks. When leaks are seen, correct the source of the leak before continuing and then re-pressurize again until the testing pressure is met, without visible leaks.
8. Record the start test pressure, then observe and wait until the required testing duration has lapsed.
9. If the pressure drops more than the maximum allowable pressure drop, the pressure testing fails. Correction and retests shall be done until the required pressure drop is within the allowable pressure drop.
10. The pipe system tested shall pass only if it meets the allowable required pressure drop under the required testing pressure for the required test duration.
11. Record and archive the test results and making sure that the same is signed by respective parties especially from the authorized representative of the owner and the contractor.
12. Submit copies to respective parties for their documentation. The test is complete!
Author:
Ar. James Ray L. Magdadaro, NAMPAP, ASPE
Registered and Licensed Master Plumber
PRC Reg. No. 6491
Leakage on plastic piping or even in steel piping is due mainly on Bolt torqueing and Gasket & Flange preservation Handling. Gasket must be preserved properly, Flange face must be protected during transport and storage, Bolts must be tighten using torque wrench and in alternating opposite sequence. Follow recommended torque published by manufacturer.
Thanks James..