3" or 4" line to Septic Tank?

Question

We are in the Process of installing a new Septic Tank and wanted people's opinions on if I should have a 3" line to the Tank or a 4" line to the tank?

I've heard that the 3" is 1/4" per foot Drop and with the steeper sides allows the solids to be carried away easier with less liquid. Clogs a bit more then a 4"

I'm heard that the 4" is 1/8" per foot Drop. With the shallower sides it would allow the liquid to run away from the solids much faster and would hardly ever clog.

So it seems like there are plusses and minuses to both. I'm going about 80' from the house to the tank and have the 1/4" drop that I would need for 4"

Suggestions? Comments?

Thanks!

lee houston · Accepted Answer

80 feet is a long run. Go with the 4" and use your 1/4" drop for bestflow.lee h

cornytheclown · Answer

Around here in northeast tennessee 4 inch is the minimum size you canrun once you leave the house......ther is probably a reason for that ~:>

Scott Townsend · Answer

Thanks Guys!!  4" it is.Now for the Secondary Question...  (-;We are adding a Granny unit to the main house and they want us to have the main house tank drain into the Sump Tank for the New Granny unit, then pump both up to the leach field.I have another 60-70' run that Will be from an Existing line of unknown size to a Sump Tank. Should that also be 4"?  It only going to be the liquid from the second chamber of the primary tank.We have yet to find the line, so thats why I dont know the size yet. I just wanted to make the hardware run today and get all the material.Thanks again!

George E. Cawthon · Answer

And put a clean out every 20 feet.

Scott Townsend · Answer

every 20'???Hmmm... Seems Excessive?  We were thinking of one right at the exit of the home, then its pretty much a straight shot to the tank.   Would look funny with 4 cleanouts sprinkled throughout the yard?Thanks!

HeyBub · Answer

Set a Bar-B-Que on the first, a rock garden on the second, and a bird-bath on the third.You'll have a hard time going eighty feed with a fifty-foot snake.

lee houston · Answer

electric motor powered snakes from rental place can go 100 ft.lee h

Al Bundy · Answer

"HeyBub"  wrote innews:     LOL. Good one.

PSZach · Answer

and wantedYour slope or fall will be 20? at ¼? per foot. Try to dismiss this olddebate ofsolids being left behind swiftly moving liquids. Concentrateon atrue/consistent slope without ?bellies?. Install at least 2cleanouts withaccess at grade level. A 4? line will allow for futureneeds and improvements.I would recommend 'ABS drain products'() such as these.

HerHusband · Answer

I would use 4" from the house to the tank, 3" for main lines inside the house. Remember to put a cleanout tee near the outside of the foundation for easy maintenance in the future.

3" is supposed to work better with today's low flow toilets, as a 4" pipe lets the smaller amount of water spread out too thin to carry the solids away. Of course, anything that does get left behind usually gets washed away with the next flush, laundry, shower, or sink usage...

1/4" per foot is about the ideal slope regardless of pipe size. But, you can get by with 1/8" per foot on larger pipe if you have longer distances to cover. 1/4" per foot would require about a 20 inch drop over your 80 feet. 1/8" per foot would only need about a 10 inch drop for the same 80 feet.

I'd still choose the 1/4" per foot slope if you have the height to accomodate it.

Anthony

3" or 4" line to Septic Tank?

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