Q&A / 

How to Slope Drain Lines

How To Slope Drain Lines TIPS

Jennifer Brown, who lives in Panama City, FL, purchased a new home that's got some serious plumbing issues. Read this:

"We purchased a new home about a year ago and have had non-stop plumbing issues. After months of the plumber coming out and telling us there was no problem, it was discovered that one of our pipes was completely level, and since we have a gravity-fed sewer system, the waste was not flowing out to the main line.

After digging up our slab and fixing the slope on one of the pipes, we stopped having sewage back ups but still smelled sewer gas in our laundry room when we used the washing machine. After having the plumber come out once again, he determined that sewage and water were sitting in our pipes.

We are afraid that this is an indication of another pipe that does not have the proper slope. Our builder keeps telling us that it is normal for sewage and water to sit in these pipes since this a gravity-fed system.

Is this correct? The plumber that took video of our line showed us the standing water and waste an indicated that this shouldn't be happening.

I was hoping you could help me because I don't know enough about these types of issues to know if the builder is just trying to save money by not fixing this problem. Any insight would be greatly appreciated."

CLICK HERE to get FREE & FAST BIDS from local plumbers who can install drain lines that slope.

Master Plumber Tim

I've had a very interesting journey. I'm a college-trained geologist, I became a master plumber before the age of 30 and then did custom building.

Because I'm all of the above, I feel I can speak to Jennifer's issue.

Scam Artists

Jennifer, the builder, and his plumber, are IDIOTS and SCAMMERS- and you can quote me on this. I'll also add the Panama City plumbing / building inspectors to the Idiot List too.

Pipes Must Slope

Plumbing AND vent lines are all supposed to be installed with pitch or fall. The generally accepted minimum pitch is 1/8 inch per foot of run.

You can also install pipes with 1/4 inch of fall per foot of run, but I'd be careful about exceeding that slope.

Vent Line Slope

Many homeowners are unaware of the network of vent lines that are part of a plumbing system. You almost always have as much pipe in vent lines as you do in drain lines.

While the vent lines are designed to deliver air to the system from the roof vent pipe, water vapor routinely condenses in the pipes.

This condensate must be allowed to drain back to the sewer or septic tank so the vent lines also must have a minimum fall of 1/8-inch per foot. 

CLICK HERE to get FREE & FAST BIDS from local plumbers who can install drain lines that slope.

Vent Piping Video

Watch this video to see the vast network of vent pipes in a house I plumbed in New Hampshire in 2016.

Too Much Creates Clogs

Plumbing drain lines that are pitched too steeply can clog because the liquids outrun the solids in the pipe. A slope of 1/4-inch per foot of run will ensure you never have issues.

Plumbing Rough-In Diagram

This is a  drawing I made to show you the drain and vent lines in a full bathroom that was to be added to an existing home.

I'm a master plumber and I drew this in about ten minutes. It shows the fixtures in a bathroom that's being added to an existing home. The solid lines carry water and waste. The dashed lines only carry air and some condensation water. (C) Copyright 2017 Tim Carter - Master Plumber

CLICK HERE to read the informative column about plumbing rough-in drawings.

Tough Love Conversation

If I could be a tiny imp on your shoulder whispering in your ear when you next have these two noobs over at your house I think the conversation might go like this:

"Mr. Builder and Plumber. The last time you were here, you said it's normal for plumbing lines to be level, right?"

"Ms. Brown, that's correct."

"Well, I did some research. I talked with the local plumbing inspector and he gave me a copy of the code book. It states right there that all drain and vent lines MUST have slope to them so there is no standing water.

Furthermore, I talked with the head of the local sewage department here in Panama City. I asked him if it's a good idea to install sewer lines level. He CRACKED UP LAUGHING saying the sewer lines would rapidly clog up. What say you?"

(Shuffling of feet, throat-clearing noises, eyes pointed to ground) "Well, that's just someone's else's opinion."

"So how about Mother Nature? In the REAL WORLD all drain lines (brooks, streams, creeks and rivers) have SLOPE. Basins that have no slope like ponds, lakes and lagoons eventually FILL UP WITH sediment because there is no slope or fall to them. I want you to fix EVERY drain line in my house that doesn't have the proper fall to it."

Game, set and match.

CLICK HERE to get FREE & FAST BIDS from local plumbers who can install drain lines that slope.


7 Responses to How to Slope Drain Lines

  1. Please ask Jennifer to give us an update after she speaks to those folks. I'm really interested in knowing the outcome. Please and thanks. franne

  2. There are a lot of incompetent "craftsmen" out there, and the average consumer doesn't know enough about the issue so they get away with it. I once had a person who installed sheetrock in a house I was building tell me the seams that were showing were "normal" and would go away on their own after a few months. Needless to say, he did the job over.

  3. I purchased my house 4 years ago. I made upgrades to already working features to give it my own personal touch. Several months ago, the kitchen drain was getting slow. I tried everything including baking soda and vinegar, Liquid Plumber, Drano Max, and even Pepsi Cola. It got worse. Finally, it stopped draining. I tried plunging and running a 25 foot snake down the drain. Nothing. I went down to the basement to see where 25 feet of snake got me. I looked at the run of the drain that started at the sink and ended at the lead into the main. The pipe was over cabinets that wee over a work bench. Ontop of the cabinet was a block of wood that held up the drain pipe. Between this block and the lead from the sink, you could see that the drain pipe bowed. And, to my surprise, there were no pipe hangers securing the drain and creating an angle. I went out and got a 50 foot snake. I removed the drain pipe that was connected to the lead to the main, I snaked the pipe that was clogged about 26 feet from the sink! I reconnected the pipe and installed pipe hangers that I purchased when I bought the snake. The angle of the pipe is crucial. Luckily, I got it right . But, reading Tim's story, he didn't mention pipe hangers. These are import to correcting the angle problem. I used the plastic "J" hangers I found at Lowes. I used a smaller size to secure water and heating lines to avoid rattling. Just some info to pass along.

  4. I could not help but commenting Tim on your response to this situation as it is a good reminder to me here in Costa Rica that we don't actually have all the idiots here. Electrical and plumbing standards are basically horrible here with next to zero in inspections.

    One rescue mission we did was in a new building for a restaurant/hotel under construction where we took over from the 3 Stooges. They had a 16' toilet line running horizontal to the stack that sloped 3" back to the toilet forget about just being level. Apparently they though crap actually runs up hill. And how many vents ZERO! This is not a tough science just an unyielding one.

    It would be most curious to hear the next responses to this line of insanity from these two stooges.

    Trevor Chilton

  5. A year or two ago a bathtub drain clogged up and with my regular plumber not available I called RotoRooter. Guy came over, ran his snake for a while very noisily, and proclaimed the drain open He ran some water, and sure - the tub quickly emptied.

    All into the downstairs bathroom, unfortunately. His full speed ahead snake work smashed open the drain. I was finally able to get my regular plumber to come over and clean up the mess, and R R returned my payment but never paid for the work my plumber had to do.

  6. For almost 30 years I worked as a senior commercial lines underwriter for 3 major insurance companies. Sounds like Jennifer had the house built. Hopefully, somewhere in her paperwork with the GC, he has shown some info re his commercial lines policies. She may be lucky and have a "certificate of insurance" (COI) that spells out who his wok comp and "GENERAL LIABILITY" is insured by. If so, she just needs to call either his insurance agent or the company and submit a GL loss! In the claim she would explain how she was told level sewer pipes where just fine on a gravity system. Her claim is for the money it will cost to repair all of the damages and reimburse her for any money already spent to fix the problem. And she may want to give her GC a call telling him she HAS submitted the claim. For anyone reading this, if you have any major job around your house then you really need a COI. This will protect yourself plus it proves the contractor is not a gypsy. BTW, a COI could have helped R Troy get his money back when he paid his plumber what he charged to fix the crappy (pun intended) work.

Leave a Reply

You have to agree to the comment policy.