Ask the Builder: Putting in plumbing drain pipes

I’ve always loved being a plumber because it’s a very interesting three dimensional challenge to install plumbing, drain and vent piping in a new house or in a major remodel. Being also the lead carpenter and builder on my jobs allowed me to think ahead to make sure all the frames and raw wood were installed so it didn’t have to be butchered to get into the pipes.

Last month, Amanda, who lives in South Carolina, reached out to me. She wanted to know how she could get money from the original plumber who installed the plumbing in her house. Amanda received bad advice from another plumber or remodeler who told her a toilet drain pipe was installed incorrectly by the original plumber.

Amanda paid the new plumber to cut out the perfectly fine pipes and install new ones with smoother bends in them. Too bad she wasted so much money! She could have spent less than $50 and scheduled a simple phone call to see if she could get any good advice. But that’s water over the dam.

Here was Amanda’s situation. The toilet drain pipe ran about 5 feet between two floor joists. It was then turned down with a regular 90-degree connector — some call it a short bent L — and immediately connected to a curved 90-degree connector rotated 90 degrees to allow the toilet waste to continue its journey to the sewage treatment plant below Floor joists, but now perpendicular to the joists.

She was told that the short 90 was inappropriate. I asked her if she had ever had constipation in the eight years since the house was built. Her answer was no. That’s why she never had constipation. The short 90 degree fitting is similar to the exact change in direction of the toilet drain that it would encounter if the pipe were connected to a standard tee fitting. Plumbers have installed horizontal toilet drainpipes connected to tees for many decades.

When you flush the toilet, the water and waste flow straight down and immediately hit a 90 degree fitting under the toilet flange. This 90 degree fitting directs the water horizontally toward the tee that is maybe 1 or 2 feet away. When the sewage reaches the middle of the tee, it makes a sharp turn and flows back down. Imagine a river flowing over a waterfall. This is a perfectly acceptable configuration – after all, it has worked well for Mother Nature for millions of years.

Rip out the plaster or drywall and you’ll find this exact configuration in millions of homes and buildings across the United States. Plumbers have used tees since the early 1900s and still use them today. In fact, I used this exact configuration two years ago when I recorded my video on flushable wipes.

In many situations, the vertical pipe exiting the bottom of the tee is just a vertical stack. This pipe could be 8 or 9 feet tall. Think of a sanitary fireplace as a chimney. Sewage goes down the chimney while smoke goes up a chimney.

At the bottom of the stacks it is best to install a Sweep 90 fitting. These fittings have a slightly larger radius than a short 90 fitting. The longer radius is very friendly to pipe cleaning snakes. This is exactly why plumbers have been using Sweep 90 fittings for decades.

In Amanda’s situation, she had an acceptable piping setup. It’s just that her stack was only 3 inches tall. Nothing wrong with that. I’ve done this before where I needed to tuck a horizontal drain pipe against floor joists in a basement or crawl space. I’ve never had problems with constipation.

It’s possible that Amanda misunderstood the advice that was given to her, or that the plumber who gave the advice wasn’t clear. Any direction change fittings routed under a ceiling should not have 90 degree fittings. If you need to change direction under concrete or other underground pipe conditions, e.g. B. in a sewer line, use two 45 degree fittings. Best practice is to separate the 45 degree connectors by at least 6 inches if possible. This is a tool for draining cleaning snakes.

You can have a 90 degree faucet under a slab, but it must either be at the bottom of a stack, as I described earlier, or it can be under a toilet that sits on a slab. If a clog occurs in either of these locations, it is usually cleared by installing a cleaning tee just above the base of the chimney, or removing the toilet to inspect the 90 degree fitting.

If you want to learn more about plumbing drain lines or the mystical plumbing vent lines, I have several videos for you on my website, askthebuilder.com. Simply enter “sanitary videos” into the search engine there. If you have questions about your drainpipes, look for the Ask Tim navigation link and enter your question for me. I’m happy to help you save time and money.

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