Septic Main Sewer Line

[Pettrix]

Design stage for my main house which will tie into an existing septic tank.

The main sewer line looks like it will be a 4" line with a run from the house to the tank of about 150'. There is a natural grade drop of approximately 3-4 feet from the house to the tank.

Local code calls for a minimum 1/8" drop for a 4" main or preferably a 1/4" drop, every 10 feet.

So are my calcs correct? From the house to the tank, if I go with a 1/4" (0.25) drop, I would need a drop of 3.75 feet from the house to the tank?

 

[outinthetalgrass]

My calculator says 3.75 inches
.25 for 10 feet
150 feet = 15 10’ sections
So 15*.25 = 3.75”

 

[grsthegreat]

first make sure they will even allow a tank that far away. here in Idaho they wont. the tank HAS to be within 30 feet of the structure.

 

[PILOON]

Yep, you'd meet the norms.
You don't want too fast a drop either, just enough to keep things flowing.
Glue/seal all joints to assure no roots get in there. Use sand to embed the drain line.

 

[Beeenvenue]

Sounds like too far away. You can extend the discharge lines from the tank but never heard of a tank being that far. Be sure to check with a real septic company - if you get this wrong you’re in deep ****

 

[grsthegreat]

i was just trying to imagine a log jamb created from flushing a 1 gallon toilet and expecting it to flow 150 feet is all im saying. but who knows, it may be totally legit. on my own house the sewer pipe exits the house 2 feet below ground level to start with. the tank is 10 feet away and the connection point is about 3.5 feet below ground level.

 

[ruffdog]

i was just trying to imagine a log jamb created from flushing a 1 gallon toilet and expecting it to flow 150 feet is all im saying. but who knows, it may be totally legit. on my own house the sewer pipe exits the house 2 feet below ground level to start with. the tank is 10 feet away and the connection point is about 3.5 feet below ground level.

"log jamb"......thanks for the visual picture. I wondered the same thing. Any bit of goop stuck in the pipe (grease) will start that log jam.

 

[Pettrix]

Building department has no issues with 150 foot length. As long as its a 4 inch line with the correct drop.

Remember, city sewer lines are 100s and 1,000s of feet at times, depending on where the main and trunk lines are located.

 

[EddieWalker]

Back in the day when sewer lines where clay or cast iron, there was a lot of issues with solid not flowing well and toilet paper building up until there was a blockage. With modern PVC sewer pipe being so smooth on the inside, this just doesn't happen anymore. The same is true with slope, it used to be really critical to get it just right, but with PVC being so smooth, everything flows down it pretty good if there is a any slope, or a lot of slope.

 

[grsthegreat]

my brother in law is a plumber in calif. he makes so much $$$ from clearing main lines, its put alot of scratch in the bank. along with cabin in snow country, new trucks, kids college funds.

Good $$ in stuck log jambs.

Around here the top of septic tank cannot be deeper than 48" from surface. the input hole is about 12" below that. so depending on slope, i guess you could go quite a ways away from house. My place isnt sloped (the ONLY reason i bought this place was because it was flat as i HATE sloped land).

 

[Pettrix]

My calculator says 3.75 inches
.25 for 10 feet
150 feet = 15 10 sections
So 15*.25 = 3.75納/QUOTE]


I swapped inches for feet so my 3.75 was feet, not inches, but you are correct. It's 3.75 inches

 

[bnold]

1/8” per foot is typical for plumbing

150’x1/8” per foot = 18.75” fall

1% is typical for site sewer lines...
1% @ 150’ = 1.5’ or 18” fall

 

[PILOON]

Re slopes:
You also don't want too steep a slope as the sewage will rush downhill and pile up to create a jamb.
Another precaution is to make clean cuts when joining fittings and even de burring the inside edges.
I like a chopsaw for perfect cuts.
As to de burring, I've seen burrs and rough cuts catch and trap J cloths rags etc that occasionally find their way in there.

 

[MossRoad]

Don't forget about putting in enough cleanouts on long lines either. Snakes are only so long.

 

[riptides]

Don't forget about putting in enough cleanouts on long lines either. Snakes are only so long.

Good one.

 

[4570Man]

Don't forget about putting in enough cleanouts on long lines either. Snakes are only so long.

I’m not sure what the distance is but it’s code to have clean outs in it at that distance.

 

[MossRoad]

It's also a good idea to have a cleanout directly outside the house regardless of distance to the septic tank, street hookup, etc... it keeps the goop outside of the house if there's a need to use it.

 

[4570Man]

It's also a good idea to have a cleanout directly outside the house regardless of distance to the septic tank, street hookup, etc... it keeps the goop outside of the house if there's a need to use it.

I never do. It’s code to have one within 10’ of where the line exists the house on the inside and I usually put the tank within 10’ of the structure so 20’ max distance. My experience is the #1 clog location is the baffle at the pipe exit inside the tank.

 

[MossRoad]

I never do. It’s code to have one within 10’ of where the line exists the house on the inside and I usually put the tank within 10’ of the structure so 20’ max distance. My experience is the #1 clog location is the baffle at the pipe exit inside the tank.

Yes, however, we're talking about long runs in this thread, not 10' from the structure. Regardless, I'd rather have a plumber snake a pipe from outside my house than in my basement.

 

[Ford850]

Main septic lines are usually required to have 1/8” - 1/4” fall per foot, not 10’.
1/8” - 1/4” fall per 10’ is usually for drainage tile (water).