Go to How Not to Build an Addition Index! This page includes notes on the waste drain test.


Of all inspections, the toughest is the waste/drain inspection. This is the only one that requires a test.

To perform the test, you will be required to plug the drain system, then fill it with water. The criterion is simple: if it does not leak after twenty minutes, you pass. If it drips, sprays, dribbles, seeps, sweats or doesn't show up at class on time, you fail.

It sounds simple enough. Yet, like everything else in life and building, there is a complication. Your new system and old systems are now interconnected. To fill the drain system to the top of the stack means that you are going to have to plug every fixture connected to the main stack. In most homes, this means ALL the fixtures. Plugging is simple on addition drains; they do not have tubs or sinks attached. However, try plugging a bath tub in the old part of the house. It has two drains. The one on the bottom of the tub is easy, but what about the overflow drain? What about the overflow drain in the sink for that matter? Worse, to keep the toilet from backing up, it must be completely removed and a plug placed in the drain below it. This is grating work, made more grating by the knowledge that this part of the system already works. It has worked for thirty years!

I solved the drain-plug-in-the-tub problem by constructing a special gasket to fit in the overflow drain. It was made of rubber, sheet metal, plywood, silicone caulk and a few screws. In retrospect, it might have been easier to simply pull out the tub.

I did not leave the drain test to chance. I decided to test it myself in advance. I got a balloon plug from the plumbing supply store and drain stops for every aperture in the house.

The neighbors will think you eccentric when they see you climb onto the roof with a garden hose. They will think you are crazy when you spray it down the vent pipe. I was up and down that ladder once every minute to check the filling process and to see if there were any leaks. There was only one, and that was in the bathtub with my makeshift plug. However, it was minor and was corrected with the application of more caulk.

I kept filling. After an hour, I thought the drain would never fill. Getting suspicious, I decided to trace the drain system to see if I had somehow missed something and the water was getting past my plug.

This proved to be the case. I found a vent pipe cross-connected a bathroom sink with the clothes washer and that the water was getting into the waste drain below my plug.

In spite of the circumvention of my drain plug, I had managed to build a column of water in the pipes about fifteen feet high. A fair amount of pressure was generated on the balloon plug. This was not a problem for the plug. However, it proved to be a problem for me when I released the air from the plug.

The plug was situated inside the pipe, and was next to the floor. To get to it, I had to kneel on the floor and reach inside the four-inch pipe through a tee. When I released the pressure in the balloon plug, the water was diverted from its natural downward flow by my arm and the now deflated balloon plug, which lodged in the tee. Water went up the sleeve of my shirt, over my chest and throughout the laundry room. In spite of my struggles, the room was flooded before I could clear the blockage.

I had failed the self-test, not because of a leak in the system, but a legitimate cross-connection that came into the system above and below the lowest possible plug. There was only one thing to do: I had to plug the cross connect. I put another tee into the system. It took two more Mission transition no-hub shielded couplings and four hours of cutting with a keyhole saw. (I wasn't about to go back to the rent-all store for that pipe cutter again. I might be put under investigation for mass murder.)

I ended up filling and emptying the system three times before I passed the self-test. Other problems included a blown plug in the toilet, which led to my first experience with geysers, and some seepage past the bell and hub in the old cast iron stack. When the inspector finally got to see my work on the drain system, he was impressed. Making allowances for a few dead ends, he even passed the mess in the crawl space. Unfortunately, the diameter pipe I had used for the hot water supply in the new bathroom was too small. Before he would pass my work, I had to tear out and replace about twenty feet of pipe.


Most inspectors at least pretend to be sympathetic to your cause. Though they are not subject to bribery, they will come back and give you a fair evaluation the second, third and fourth time.

If I learned nothing else from the inspection process, I learned perseverance. A failed inspection is only a temporary set-back, and success is inevitable with the application of time, energy and mulish bullheadedness. Next Page


See below to order the book!

Introduction | Decision Making | Design | Permits | Buying Materials | Demolition | Digging | Masonry | Framing | Electricity | Plumbing | Inspections | Roofing | Sheathing / Siding | Soffits | Insurance | Insulation | Fat Fireman Rule | Drywall | Finish Carpentry | Tile | Painting | Carpet | Done

About the Author:
W.J. Rayment built an addition on his house, and in the course of the project learned from his many mistakes. This on-line compendium is his effort to help you learn from his experience. The advice and stories are often humorous, sometimes silly, but always informative. for yourself or as a gift for family or friends.

Contact Us | Privacy Statement