30th May 2023
In this blog we take a look at the requirements for drain testing.
One of the commissioning and test certificates we are likely to ask you for is evidence of drain testing, and failure to provide it will hold up the issuing of the final certificate.
The requirement for drain testing is clearly set out in the Building Regulations and can be found in Approved Document H sections 1.38 and 2.59-2.62, with further guidance in BS 8000 Pt 13, BS EN 752, and BS EN 12056.
We often get asked why we insist on the test, as some builders will claim that they haven’t been asked to do one before. Not all Building Inspectors are as thorough as us and may apply a light touch to the regulations.
However, it’s in everyone’s interest to make sure that they are tested. After all the purpose of the tests are to make sure that the drains aren’t blocked or leaking. As a homeowner, I’m sure you will agree that it’s well worth getting the drains tested, as no-one wants smells, leaks or raw sewage backing up into their house, and the problems may not become apparent until the builder has long left site. For the builder it also proves that there wasn’t a problem with the drainage when they left site, providing protection against a claim for defective work.
When to test
The tests are performed by the builder or plumber before the drains are covered up and again at completion. It’s the test at completion that’s most important, as the drains can be damaged or blocked during the course of the works. Unfortunately, it’s not uncommon for paint, plaster or other materials to be tipped down the toilet, and these won’t be detected from the earlier test.
Types of Test
Below Ground Drainage
For below ground drainage there are 3 main ways to test that everything is OK.
Air Test: This is a quick and efficient method to check if pipes and drain runs are working properly. A section of the drain is sealed with two gauges, and air is pumped in to increase the pressure. The pressure readings are monitored for changes, which might indicate a problem.
Water Test: This is a slower method that might take up to 2 hours to set up, but it allows testing a whole system at once. The ends of the system are sealed, and water is charged into the system. The water levels are then monitored from an access point.
CCTV test: The test involves inserting a small high-tech camera into the drains which will then capture real-time footage. From the CCTV footage, you can see if there are any cracks, displaced joints, signs of poor installation (such as joining the wrong materials) or blockages. See example here. The CCTV test can also help ensure that the new drainage has been correctly connected to the foul or surface water sewer if you are on a separate system. A CCTV test can also be performed before works commence as this will give you valuable information on the condition and location of your existing drains.
Above Ground Drainage
For above ground drainage (also known as an SVP, Soil Stack, or Sanitary Pipework Test ) the main method is the Air test (see above). However, in larger projects we may also ask for a discharge or self-siphonage test.
Discharge test: To test for the effect of self-siphonage the appliance should be filled to overflowing level and discharged by removing the plug; WC pans should be flushed. Ranges of appliances, connected to a common discharge pipe, scan also be tested for induced siphonage in a similar way. Then the level of water remaining in the trap is measured to make sure that the traps have not “pulled” or emptied out as this will allow smells out of the drains and into your home.