Last month on the Danco blog, we covered the basics of your home’s Drain-Waste-Vent plumbing system, aka the DWV system. Now that you understand the purpose and function of your home’s DWV system, you’re ready to dive in a bit deeper and learn how to test it for leaks.

Why Might I Need to Test My DWV System?

An airtight DWV plumbing system is essential for a safe home. Leaks could lead to sewer gases filling your home, which not only smell terrible, but are potentially toxic as well.

To avoid leaking gases, and failing city plumbing code regulations, you’ll need to test your system, and ensure it’s airtight.

How Do I Test My DWV System?

You have two main options available to you for testing DWV systems: water-pressure and air-pressure.

Air Pressure Test

Air pressure tests work best if you are testing a newly installed DWV system, that hasn’t been connected to the sewer line yet, or if you need to test in sub-zero temperatures.

Your first step is to locate all the clean-out plugs.

Clean-outs are Y-shaped fittings found in floor drains, under sinks and along the DWV system. They’re placed to give plumbers easy access to use plumbing snakes in case of clogs. Clean-outs are capped with plugs with square nuts, which you can tighten with a wrench.

Your second step is to tighten all of these plugs except one.

(NOTE: It is not uncommon to find rusted or faulty plugs, or drains that are missing plugs entirely! If you run across any of these issues, you’ll need to purchase a new DWV test plug to close the gap. Check out Danco’s new product, the PlugAll™ – a 4-in-1 DWV test plug that will perfectly serve your needs!)

Once you’ve tightened all the clean-out plugs except one, remove the cap from the last plug, and insert your air compressor. Fill the pipes to a pressure of 5psi, then turn off the compressor.

Watch the air-pressure reading for 15 minutes. If the pressure drops at all, then you have a leak in the pipes.

Water Pressure Test

If your DWV system is already connected to the sewer line, and/or you’ve already installed plumbing fixtures, your best option is to perform a water pressure test.

Like the air pressure test, the water pressure test begins with locating and tightening the clean-out plugs. This time, tighten all of them.

Next, shut off your system’s main shut-off valve, then attach a pressure gauge to an outside or laundry faucet.

Turn the faucet fully on, then watch the pressure gauge for 15 minutes. If the pressure drops, but none of your faucets are leaking, then you have a leak in your pipes.


DWV systems can be tricky, and as stated above, an airtight system is essential for a safe and healthy home. So, if either of these tests indicate your system has a leak, call in a professional plumber to help.