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Minimize Clogged Drains – Plumbing Installation Tips

Installing Plumbing to Minimize Clogs

I have been a licensed master plumber for nearly 20 years. It has been a learning experience the entire way. I have learned from my mistakes. I also have learned some tips from seasoned plumbers and sharp inspectors. Here are some plumbing installation tips that may help you minimize clogs.

Bigger is Not Always Better

Some people think that if you oversize piping you will have fewer clogs. Actually, the opposite is true. Large diameter pipes spread out the energy of the moving water. Keep in mind that the weight of the water moving through drainage pipes under the influence of gravity is the locomotive force propelling solid waste into the sewer or septic system. A large pipe allows water to spread out along the bottom portion of the pipe. A smaller pipe handling the same volume of drain water will pick up and carry solid waste faster and farther. Smaller diameter pipes concentrate this energy and help to quickly move solid waste through the system.

Plumbing codes regulate pipe sizes and attach a value to each fixture. These are often called fixture units. Toilets obviously discharge much more water at a faster rate than a drinking fountain. As such, toilets need a large pipe size to handle the solid waste and large amount of water. Three inch pipes are used to handle most residential toilets. 1.5 inch lines are used to handle waste from kitchen, bathroom and powder room sinks. 2 inch drain lines are common pipes for laundry drains.

Clogs can develop easily on horizontal runs of pipe. Friction causes the water within the pipe to slow down. To achieve good water flow, try to install horizontal drain pipes so they have a minimum of 1/4 inch per foot slope. 3/8 of an inch per foot is actually better.

No Hard 90's Under Ground!

Sharp bends in piping also slow down water movement. They cause the moving water to loose energy. The 90 degree bends also are tough to pass through with drain cleaning equipment.

Never install a 90 degree fitting under ground except when used at the base of a vertical plumbing stack. This is where a vertical pipe turns and goes horizontal. If you have to turn 90 degrees, use two 45 degree angle fittings separated by a 12 or 18 inch piece of straight pipe.

Tub and Shower Drains

When I installed my kids tub drain piping 12 years ago, I had a feeling trouble was brewing. I clearly remember thinking that because of the way I had to twist the 1.5 inch trap and piping around in the tight joist bay, there could be problems. Sure enough, when the tub stopped up, I couldn't get a plumbing snake through the line.

I would have had much better success if I had installed a 2 inch trap and branch line to the primary drain stack. That is my advice to you - use 2 inch traps and drain piping for bathtubs. Most plumbing codes mandate that shower stalls use 2 inch piping and traps. It only makes sense for tubs to be piped in a similar manner. The 2 inch traps accept drain cleaning snakes more readily.

Cleanouts - Test Tees

Where ever possible, make sure you install a cleanout or test tee within visible horizontal runs. Install the fitting so the access plug is not pointed down. Turn it slightly up from the horizontal position. You may never need to use the cleanout, but will thank your lucky stars if there is a clog!

Don't Guess

If you are trying to install your own plumbing system, don't guess at pipe sizes. Get a copy of a code book to make sure you are using the correct sized piping. Check to see if you are even allowed to install plumbing. Some states have highly restrictive laws that do not permit DIY work.

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4 Responses to Minimize Clogged Drains – Plumbing Installation Tips

  1. After flushing my upstairs toilet, I hear a rumble and banging as the water goes down the pipe. I checked the pipe and its solidly attached but has a 90 degree bend at the bottom. Would that be the cause of rumbling and sometime few bangs?

  2. Likely that your roof vent is clogged between the toilet and the roof of your house, snake out the vent and you should be good to go.

  3. Can v place a 1 1/2 inch net at the mouth of the start of 4 inch under ground sewer pipe to stop the clogging under ground?

    • Yes, you can do whatever you want. If you want to do that, go ahead. The power is always is the questions.

      You should have asked: "Tim, is it a wise idea to put a screen in front of an underground pipe to stop clogging?"

      That answer is a resounding NO.

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