On Oct 31, 3:00*am, harry wrote:
On Oct 30, 9:23*pm, RicodJour wrote:





On Oct 30, 2:36*pm, lj wrote:

On Oct 30, 9:49*am, RicodJour wrote:

On Oct 30, 9:29*am, lj wrote:

On Oct 30, 4:57*am, harry wrote:

On Oct 29, 11:53*pm, mike wrote:

Just because I'm sick of seeing the liquids-outrunning-solids-on-steep-
slopes myth on the net....

http://www.pmmag.com/CDA/Archives/83...M100000f932a8c...

"A few years later I took a college course that we nicknamed Sewer
101. You got it; the course was on the design of sewers and sewage
treatment facilities. The professor was explaining the installation of
sewers in steep terrain. He was suggesting that we change piping
materials for sewers that were pitched more than 30 degrees.

I raised my hand wondering about the problems that would be
encountered. My mind was abuzz with whether my father was right, or
the plumbing inspector was right. I asked, "If you pitch the pipe too
much, won't the liquids run away from the solids, resulting in an
increased amount of stoppages?"

The professor started laughing as I tried to disappear under my desk.
He said, "You're a plumber, right?" He already knew I was because we
had talked about it many times. "Yeah," is all I could say.

"I don't know why they always teach plumbers that myth. Maybe it is
because they want them to install perfectly aligned sewers."

Of course, I found out that the professor was setting me up. This lead
to the presentation of a new equation. The equation calculated the
minimum flow rate to keep solids in suspension in a sewer system. The
inverse of the equation calculated the maximum pitch before the
liquids ran away from the solids. Of course, the answer to the maximum
pitch was infinity. In other words, you could never reach that point.

Then the professor asked, "What is the maximum pitch we could have for
a project?" That one's easy -- a vertical stack! "Yeah, and in a
stack, the solids land at the bottom first." Excuse me?!

"You got it, the solids land first and the liquids come along and pick
them up and carry them down the drain."

Most of the students just took this all in. Me, my eyes were bulging.
This was mind-blowing stuff. All I could do was think back to that
sewer with the 350 feet of distance and 150 feet of vertical drop. The
professor just told me (indirectly, of course) that we didn't have to
put in one of those vertical drops.

If I knew then what I know now, that sewer would have been 2 feet
below grade pitch straight down that hill. The sewage would have been
humming when it hit the public sewer connection.

I have long since forgotten that equation. But I learned an important
lesson. More than 25 years later, some plumbing instructors are still
teaching that if you pitch the pipe too much, the liquid will run away
from the solids. But all of you know better.

As for that 3-inch pipe, you can pitch it 1/8 inch per foot without a
problem. Of course, at 1/4 inch per foot the flow will run faster."

We use 4" pipe (minimum) over here. *And the optimum fall is 1:30.
And it's perfectly true that if it's too steep the turds get left
behind. i have seen all this demonstrated in a system made out of
glass pipes and adjustable for various slopes at our BRE (Building
Research Inststute) So never mind the theoretical equations, this has
been determined by practical experiment.
And the turds float blunt end first.
The sharp end is to stop the cheeks of your arse clapping
together. * :-)- Hide quoted text -

- Show quoted text -

I wonder if the drag experienced by solids verses water has something
to do with it.

I have a situation where I've not been able to get optimum slope. *I
have a 3" darin between the garage and house that goes about 18'
between the joists of a deck that connects the two structures.http://www.jamesgangnc.com/housefront.jpg*I had no other way to get
the 2nd floor of the garage connected to the septic because the grade
around the garage is too low. *Tank is in front of the house. *The run
goes out under a stair landing on the garage side and through the
house wall on top of the foundation. *I even cut the pt board on top
of the house foundation where the pipe is to maximize the slope but
water poured in the garage end just barely goes through. *The start of
the run begins with a 7' straight down drop. *So I'm hoping that the
additional force from the drop will help propel it along. *All the
drains in the garage are at the top of the 7' drop so I'm thinking
that even if some solids get stopped in the middle the next drain
event will pick them up and move along.

The momentum from that 7' drop basically disappears when it hits the
horizontal run. *If the pipe were always full it would be a different
story.

Where are you that you don't have to worry about running a drainage
line outside? *It doesn't freeze up in winter? *How come you didn't
poke a hole through the foundation so there'd be more drop?

R- Hide quoted text -

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Even though I used a one of those T's with a long sweep? *You think
none of the down velocity is going to remain after it comes out of the
long sweep?

Most of the momentum will be lost in turbulence, and the rest will be
lost in the low slope situation. *I'd try to block it intentionally
and see if there will be a problem down the road.

North Carolina. *I ran it inside a piece of 5" r8 flex duct. *I figure
the septic tank is always venting warm gas. *The tank is about 8' from
the house. *The dw for the house is in a crawl that never gets much
below 50. *On the garage side it goes in right above an electric hw
tank. *It's marginal but we seldom have lows that remain below
freezing during the day so it's not going to take much to keep it from
freezing. *It's a block foundation plus I wanted to keep the pipe in
between the deck joists to further reduce it's exposure to freezing.

Hind sight and all that, I would have poked a hole in the block wall.
Easy enough to do and there'd be no question about the slope. *If it
ever becomes a problem you could still do it. *You'd only need two or
three slip couplings and half a day. *Everything else could be reused..

The only other solution would have been to pump up to the septic tank
and the garage just as a 3/4 bath that will be used occasionally. *The
grade at the garage is lower that the top of the tank. *The main house
has 3 full baths.

I did put a clean out directly in line with it on the garage end.

At every change of direction - cleanouts are your friend.

R- Hide quoted text -

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Quite right.

A septic tank eight feet from the house? * Dunno how you can stand the
stench. *They are supposed to be 30 ft away over here- Hide quoted text -

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It's closed tank. Never smell anything. The house is at a lake and
in order to be close to the corp land surrounding the lake the houses
are built on the back side of the lots. Since it's lake that's
usually the low end of the lot as well. So the field is a pump up.
Tank is huge, I guess because it has a divider and a pump inside it.