Safe Smoke Testing for Leaks in Sewer, Plumbing and Storage Tanks

Make A Smoke Pump for Leak Testing Converting A Shop Vacuum Cleaner

I get this question many times per week. Can we drop the smoke emitter in the plumbing line and locate leaks. The long and short answer is, “No”. Many sewer lines have methane in them which is extremely flammable and explosive.

IMPORTANT: Do not put a lit device into or even near, an open drain line that is connected to the sewer line or septic system. Methane is a result of or a by-product of, the waste disposal process. Yes, it is the same methane used to heat homes, cook meals etc, otherwise called Natural Gas. It is very explosive and stays low to the ground where you are working since it is heavier than air. Just a spark could ignite the leaked gas and have catastrophic results. For better and safer results use a Smoke Pump. With this method, one would burn the smoke emitter in a contained area and then pump the smoke into the duct, tank, pipe or any enclosed space to find leaks. The smoke itself is not flammable or dangerous to deliver via this method.

To make your own smoke pump most shop vacs will work, however a metal one would be my recommendation for added safety. If you want to control the pressure via the fan speed you will want to use a rheostat on the line so you can control the speed of the motor.

There are many models of smoke pumps available on the market, however they are all rather expensive and decent ones start in the thousands. For a tool that you may only use once in a while, it just may not be the right investment for you at this time. Good news is that with a little ingenuity and imagination you can build your own. I believe that if you are a person that will smoke test a plumbing stack than you must be a person that would have the ability to put something like this together, with a bit of thought. Here a few ideas to help stimulate your own plan. Build your own smoke pump from what you may have around the house or shop.

This concept works around a shop vacuum cleaner or otherwise called a shop-vac and a few other items. Basic steps to prepare the vacuum to be used as a smoke pump.

  1. Empty the debris and remove any potentially flammable dust or fragments left behind.
  2. Drill or punch many 1/8″ holes around the circumference of the can and lid. This will allow the smoke to go through the can without the ash residue.
  3. Remove the filter from the shop vac since it would filter out the smoke we are trying to deliver.
  4. Place the perforated can into the shop vac.
  5. Following the instructions; light a smoke emitter, place it into the metal can and replace the lid back on the can.
  6. Close the shop vac lid.
  7. Move the hose from the suction side onto the exhaust side.

You now have an air pump. With a few additional items and steps we can turn this into a smoke pump.

Supplies needed:

  • A clean or new metal can with lid (just like a paint can). Be careful some of the newer cans have plastic bottoms, select a 100% metal can. I prefer a 128 ounce (gallon) can, which typically measures about 10″ tall x 9″ diameter. However this size may not fit in your vacuum. In that instance and really only for the S103 and S102 size smoke bombs, one could use a 64 ounce (half gallon) can, which typically measures about 6″ tall by 5.5″ in diameter.
  • 2″ gaffers tape (or duct tape if you do not mind the tacky residue it leaves behind)
  • A Fernco (rubber coupling) to attach the hose to your plumbing stack


  • Rheostat on the line so you can control the speed of the motor (when testing a drain line with a sink in it is important to monitor the motor speed because too much pressure will compromise the fluid in the traps allowing the smoke to escape and result in a failed test).

Use white or FP smoke to avoid residue .