How to Clear a Plugged Roof Plumbing Stack


If your toilets or sinks are draining abnormally slow, and you can't find an obstruction in the waste lines, there's a good chance it's in the vent stack. The stack is the 2- or 3-inch pipe you see on the roof just above the main bathroom. If the opening doesn't have a cover, there's nothing to stop leaves, pine needles or even a small animal from blocking the flow of air that keeps water moving in your drainage system. To clear out the vent stack, you have to put on some rubber-soled shoes and climb on the roof.

Things You'll Need

  • Extension ladder
  • Ropes
  • Garden hose
  • Nozzle
  • Set an extension ladder against your house that is tall enough to extend at least 2 feet above the edge of the roof. Secure the bottom to the side of the house and the top to the roof fascia with ropes.

  • Climb on the roof and clear leaves, pine needles and other debris from around the vent opening. Reach into the opening as far as you can and pull out any debris lodged inside. If drainage improves after you do this, it may be all you need to do.

  • Screw a nozzle onto a garden hose and connect the hose to a faucet. Turn the water on all the way and climb onto the roof with the hose to clear obstructions deeper in the vent stack.

  • Point the nozzle into the vent opening and spray full force. Position someone in the house to watch the sink drains and toilets for overflowing while you do this. If any drain overflows, it means the obstruction is below it. The water will clear most obstructions, but stop spraying at the first sign of an overflow.

  • Use an auger to clear the vent if water overflows from a drain in the house or from the vent opening itself. Insert the auger head in the vent opening and push it in until you encounter resistance. Crank the handle to clear the blockage. You'll know it's clear, because the backed-up water will drain.

Tips & Warnings

  • If you get overflow from drains in the lower part of the house, you'll need a long auger with a reach of 20 feet or more to clear the blockage. You can rent one of these from a rental outlet.
  • If your roof has a pitch greater than 4/12, which means it rises 4 feet for every 12 feet of horizontal distance, don't depend on friction to support you. Install roof jacks so you can work safely.


  • Photo Credit Jupiterimages/ Images
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