How to Slope Drain Lines
Quick Column Summary:
- Level waste pipe will not drain
- Sewage in pipes causes bad smell
- Pitch and fall of pipes is crucial
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 I 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."
Because I'm a master plumber, a builder and a geologist, I feel I can speak to Jennifer's issue.
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.
Plumbing AND vent lines are all supposed to be install 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.
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.
If I could be 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.