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567

It's GOT to be more than that. It's got to be at least a 9 degree slope. All that crap and toilet paper would HAVE to clog up a 2% slope. How can a 2% slope get rid of all the waste? It just doesn't seem possible.

Who has a septic tank? I'll bet you have more than a 2% slope.

It's GOT to be more than that. It's got to be at least a 9 degree slope. All that crap and toilet paper would HAVE to clog up a 2% slope. How can a 2% slope get rid of all the waste? It just doesn't seem possible. Who has a septic tank? I'll bet you have more than a 2% slope.

(post is archived)

[–] • 5 pts

The slope is one-quarter inch per running foot of drain pipe. It was arrived at through trial and error, over time. It was observed that if the decline in the pipe was less than this, particulate matter would be left behind by the slow-flowing water and the pipe would clog up. However, if the decline was more than this, the water would run away too quickly and leave the particulate matter behind, and the pipe would clog up.

[–] • 0 pt

That's incredible. Who are these people that figured that out? They should have privilege if not worship.

[–] • 4 pts

The 2 degree drop does not start at the top of your drains. The drain first drop vertically at 0 degrees for a few inches through the foundation and the hydraulic pressure of the waste water falling will help to power the solid waste down the 2 degree grade. Water isn't compressible so a vertical drop builds up a lot of pressure when it collides with anything in the drain. This is why you can't have straight down waste water pipes in tall buildings. They limit their vertical height by redirecting it horizontally every few floors because the force of a straight down drop from 40 stories would absolutely burst the pipes and fitting at the lower floors of the building. Hydraulic pressure makes the system work well with only 2 degrees of grade for residential installations.

[–] • 0 pt

You neglected to mention the action of a siphon toilet.

But otherwise, great comment.

[–] [deleted] • 2 pts

Hmmmmm, i have heard that a 15% slope is responsible for 50% of all waste.

[–] • 2 pts

The problem is, with that kind of slope, it won't stay that way, it'll go level occasionally if it's a long run.

I'm no pro though.

[–] • 0 pt

What do you mean..."it'll go level occasionally"?

According to , it's a done deal. Trial and error.

[–] • 0 pt

Well I'm sure they know more than me. But I was in roofing for 30 years and we'd never apply roofing material (shingles) on any slope under a 4/12 pitch, because as the water runs off, it will meet with areas that are NOT the correct slope, if it was under that pitch, due to some natural flattening (for lack of better time) that happens over time.

[–] • 0 pt

Plastic drain pipes are not 100% straight, most have a bit of a bend/warp/curve. But if the run is mostly a drop of .25 inches per foot, it will work out.

[–] • 1 pt

It’s also total drop from source to end. If it falls 18” to start, anything above it pushes down with its weight from that high. You could go more and feel better if you want, won’t hurt.